NEETS Q&A

ALTERNATING CURRENT GENERATORS

Q1. Magnetic induction occurs when there is relative motion between what two elements? A1. A conductor and a magnetic field.

Q2. What is the part of an alternator in which the output voltage is generated? A2. Armature.

Q3. What are the two basic types of alternators? A3. Rotating armature and rotating field.

Q4. What is the main advantage of the rotating field alternator? A4. Output voltage is taken directly from the armature (not through brushes or slip rings). Q5. Most large alternators have a small dc generator built into them. What is its purpose? A5. To provide dc current for the rotating field.

Q6. How are alternators usually rated? A6. Kilovolt-amperes (volt amperes).

Q7. What type of prime mover requires a specially designed high-speed alternator? A7. Steam turbine. Q8. Salient-pole rotors may be used in alternators driven by what types of prime movers? A8. Internal combustion engines, water force and electric motors.

Q9. What does the term single phase indicate? A9. One voltage (one output). Q10. In single-phase alternators, in order for the voltages induced in all the armature windings to add together for a single output, how must the windings be connected? A10. In series. Q11. What determines the phase relationship between the voltages in a two-phase ac generator? A11. Placement of armature coils. Q12. How many voltage outputs are available from a two-phase three-wire alternator? A12. Three. Q13. What is the relationship of the voltage at C in figure 3-7 to the voltages at A and B? A13. C is 1.414 times greater than A or B. Q14. In a three-phase alternator, what is the phase relationship between the individual output voltages? A14. Each phase is displaced 120º from the other two. Q15. What are the two methods of connecting the outputs from a three-phase alternator to the load? A15. Wye and Delta. Q16. Ships’ generators produce 450-volt, three-phase, ac power; however, most equipment uses 117-volt, single-phase power What transformers and connections are used to convert 450-volt, threephase power to 117-volt, single-phase power? A16. Three single-phase, delta-delta, step-down transformers. Q17. What two factors determine the frequency of the output voltage of an alternator? A17. Speed of rotation and number of poles.

Q18. What is the frequency of the output voltage of an alternator with four poles that is rotated at 3600 rpm? A18. 120 Hz. Q19. The variation in output voltage as the load changes is referred to as what? How is it expressed? A19. Voltage regulation. As a percentage.

Q20. How is output voltage controlled in practical alternators? A20. By varying the voltage applied to the field windings.

Q21. What generator characteristics must be considered when alternators are synchronized for parallel operation? A21. Output voltage, frequency, and phase relationships.

ALTERNATING CURRENT MOTORS

Q1. What are the three basic types of ac motors? A1. Series, synchronous, induction.

Q2. Series motors are generally used to operate what type of equipment? A2. To power small appliances.

Q3. Why series motors are sometimes called universal motors? A3. They operate on either ac or dc. Q4. What determines the number of field poles required to establish a rotating magnetic field in a multiphase motor stator? A4. The number of phases in the applied voltage. Q5. What is the angular displacement between field poles in a two-phase motor stator?

A5. 90º .

Q6. What is the major difference between a two-phase and a three-phase stator? A6. Number and location of field poles. Q7. What requirement is the synchronous motor specifically designed to meet? A7. Constant speed required by some loads. Q8. Why is the ac induction motor used more often than other types? A8. They are simple and inexpensive to make. Q9. The speed of the rotor is always somewhat less than the speed of the rotating field. What is the difference called? A9. Slip.

Q10. What determines the amount of slip in an induction motor? A10. Load.

Q11. What type of ac motor is most widely used? A11. Single-phase induction motor.

Q12. How do split-phase induction motors become self-starting? A12. By using combinations of inductance and capacitance to apply out-of phase currents in starting windings. Q13. Why are shaded-pole motors used to drive only very small devices? A13. They have very weak starting torques.

AMPLIFIERS

Q-1. What is amplification? A-1. Amplification is the control of an output signal by an input signal so that the output signal has some (or all) of the characteristics of the input signal. The output signal is generally larger than the input signal in terms of voltage, current, or power. Q-2. Does an amplifier actually change an input signal? Why or why not? A-2. No, the input signal is unchanged, the output signal is controlled by the input signal but does not effect the actual input signal.

Q-3. Why do electronic devices use amplifiers?

A-3. To amplify the input signal to a usable level.

Q-4. In what two ways are amplifiers classified?

A-4. By function and frequency response. Q-5. What type of amplifier would be used to drive the speaker system of a record player?

A-5. An audio power amplifier. Q-6. What type of amplifier would be used to amplify the signal from a radio antenna?

A-6. An rf voltage amplifier.

Q-7. What determines the class of operation of an amplifier? A-7. The amount of time (in relation to the input signal) in which current flows in the output circuit.

Q-8. What are the four classes of operation of a transistor amplifier?

A-8. A, AB, B, C. Q-9. If the output of a circuit needs to be a complete representation of one-half of the input signal, what class of operation is indicated?

A-9. Class B operation.

Q-10. Why is class C operation more efficient than class A operation? A-10. The amplifier operates (and therefore uses power) for less time in class C than in class A.

Q-11. What class of operation has the highest fidelity?

A-11. Class A operation.

Q-12. What is the purpose of an amplifier-coupling network?

A-12. To transfer energy (a signal) from one stage to another.

Q-13. What are four methods of coupling amplifier stages?

A-13. Direct, RC, impedance, and transformer coupling.

Q-14. What is the most common form of coupling?

A-14. RC coupling. Q-15. What type coupling is usually used to couple the output from a power amplifier?

A-15. Transformer coupling.

Q-16. What type coupling would be most useful for an audio amplifier between the first and second stages?

A-16. RC coupling. Q-17. What type of coupling is most effective at high frequencies?

A-17. Impedance coupling. Q-18. What impedance relationship between the output of one circuit and the input of another circuit will provide the maximum

NEETS Q&A

power transfer?

A-18. Equal impedance. Q-19. If maximum current is desired at the input to a circuit, should the input impedance of that circuit be lower than, equal to, or higher than the output impedance of the previous stage?

A-19. Lower than. Q-20. What are the input- and output-impedance characteristics of the three transistor configurations? A-20. Common emitter-medium input, medium output; common base-low input, high output; common collector-high input, low output.

Q-21. What transistor circuit configuration should be used to match a high output impedance to a low input impedance?

A-21. Common collector. Q-22. What type of coupling is most useful for impedance matching?

A-22. Transformer coupling.

Q-23. What is feedback? A-23. The process of coupling a portion of the output of a circuit back to the circuit input.

Q-24. What are the two types of feedback?

A-24. Positive and negative or regenerative and degenerative. Q-25. What type feedback provides increased amplitude output signals?

A-25. Positive (regenerative) feedback.

Q-26. What type feedback provides the best fidelity?

A-26. Negative (degenerative) feedback. Q-27. If the feedback signal is out of phase with the input signal, what type feedback is provided?

A-27. Negative (degenerative) feedback. Q-28. What type feedback is provided by an unbypassed emitter resistor in a common-emitter transistor amplifier?

A-28. Negative (degenerative) feedback.

Q-29. What is a phase splitter? A-29. A device that provides two output signals that differ in phase from a single input signal.

Q-30. What is one use for a splitter? A-30. A phase splitter is used to provide the input signals to a push-pull amplifier.

Q-31. What is a common use for a push-pull amplifier? A-31. A push-pull amplifier is used when high power output and good fidelity are needed.

Q-32. What is the advantage of a push-pull amplifier? A-32. A push-pull amplifier provides more gain than a single transistor amplifier. Q-33. What class of operation can be used with a push-pull amplifier to provide good fidelity output signals?

A-33. Class A, Class AB or Class B operation.

AMPLITUDE MODULATION

Q-1. What is modulation? A-1. Modulation is the impressing of intelligence on a transmission medium. Q-2. What is a transmission medium? A-2. May be anything that transmits information, such as light, smoke, sound, wire lines, or radio-frequency waves. Q-3. What is heterodyning? A-3. Mixing two frequencies across a nonlinear impedance. Q-4. What is demodulation? A-4. The process of recovering intelligence from a modulated carrier. Q-5. What waveform is the basis of all complex waveforms? A-5. The sine wave. Q-6. What is the purpose of using vectors? A-6. To represent quantities that has both magnitude and direction. Q-7. What is the trigonometric ratio for the sine of an angle? A-7. Sine θ = opposite side ÷ hypotenuse. Q-8. What is the mathematical formula for computing the output voltage from a moving coil in a magnetic field? A-8. e = Emax sine θ. Q-9. What is the instantaneous amplitude of a sine wave? A-9. The value at any given point on the sine wave. Q-10. What term describes how much of a cycle has been completed? A-10. Phase or phase angle. Q-11. What determines the frequency of a sine wave? A-11. The rate at which the vector which is generating the sine wave is rotating. Q-12. What is the period of a cycle? A-12. The elapsed time from the beginning of cycle to its completion. Q-13. How do you calculate the wavelength of a sine wave? A-13. Wavelength = rate of travel × period. Q-14. Define the heterodyne principle.

A-14. Process of combining two signal frequencies in a nonlinear device. Q-15. What is a nonlinear impedance? A-15. An impedance in which the resulting current is not proportional to the applied voltage. Q-16. What is spectrum analysis? A-16. The display of electromagnetic energy that is arranged according to wavelength or frequency. Q-17. What two conditions are necessary for heterodyning to take place? A-17. At least two different frequencies applied to a nonlinear impedance. Q-18. What is amplitude modulation? A-18. Any method of modulating an electromagnetic carrier frequency by varying its amplitude in accordance with the intelligence. Q-19. What are the three requirements for cw transmission? A-19. A method of generating oscillations, a method of turning the oscillations on and off (keying), and an antenna to radiate the energy. Q-20. Name two methods of oscillator keying. A-20. Plate keying and cathode keying. Q-21. State the method used to increase the speed of keying in a cw transmitter. A-21. Machine keying. Q-22. Name three advantages of cw transmission. A-22. A high degree of clarity even under severe noise conditions, long-range operation, and narrow bandwidth. Q-23. Name a disadvantage of a single-stage cw transmitter. A-23. Antenna-to-ground capacitance can cause the oscillator frequency to vary. Q-24. What is the purpose of the power-amplifier stage in a master oscillator power amplifier cw transmitter? A-24. To isolate the oscillator from the antenna and increase the amplitude of the rf oscillations to the required output level. Q-25. What is the purpose of frequency-multiplier stages in a VHF transmitter? A-25. To raise the low frequency of a stable oscillator to the vhf range. Q-26. What is a microphone? A-26. An energy converter that changes sound energy into electrical energy. Q-27. What special electromechanical effect is the basis for carbon microphone operation? A-27. The changing resistance of carbon granules as pressure is applied to them. Q-28. What is a major disadvantage of a carbon microphone? A-28. Background hiss resulting from random changes in the resistance between individual carbon granules. Q-29. What property of a crystalline material is used in a crystal microphone? A-29. The piezoelectric effect. Q-30. What is the difference between a dynamic microphone and a magnetic microphone? A-30. A dynamic microphone has a moving coil and the magnetic microphone has a moving armature. Q-31. What are the two major sections of a typical AM transmitter? A-31. Rf and af units. Q-32. When 100 kilohertz and 5 kilohertz are heterodyned, what frequencies are present? A-32. 100 kilohertz, 5 kilohertz, 95 kilohertz, and 105 kilohertz. Q-33. What is the upper sideband of an AM transmission? A-33. All of the sum frequencies above the carrier. Q-34. Where is the intelligence in an AM transmission located? A-34. The intelligence is contained in the spacing between the carrier and sideband frequencies. Q-35. What determines the bandwidth of an AM transmission? A-35. The highest modulating frequency. Q-36. What is percent of modulation? A-36. The depth or degree of modulation. Q-37. With a single modulating tone, what is the amplitude of the sideband frequencies at 100-percent modulation? A-37. One-half the amplitude of the carrier. Q-38. What is the formula for percent of modulation?

A-38. 100%Ec

Em%M ×=

Q-39. What is high-level modulation? A-39. Modulation produced in the plate circuit of the last radio stage of the system. Q-40. For what class of operation is the final rf power amplifier of a plate-modulator circuit biased? A-40. Class C. Q-41. The modulator is required to be what kind of a circuit stage in a plate modulator? A-41. Power amplifier. Q-42. How much must the fpa plate current vary to produce 100-percent modulation in a plate modulator? A-42. Between 0 and nearly two times its unmodulated value.

NEETS Q&A

Q-43. The collector-injection modulator is similar to what type of tube modulator? A-43. Plate modulator. Q-44. When is a control-grid modulator used? A-44. In cases when the use of a minimum of af modulator power is desired. Q-45. What type of modulator is the cathode modulator (low- or high-level)? A-45. Low-level. Q-46. What causes the change in collector current in an emitter-injection modulator? A-46. Gain is varied by changing the voltage on the emitter.

ANGLE AND PULSE MODULATION

Q-1. What are the two types of angle modulation?

A-1. Frequency and phase. Q-2. Name the modulation system in which the frequency alternates between two discrete values in response to the opening and closing of a key?

A-2. Frequency-shift keying. Q-3. What is the primary advantage of an fsk transmission system?

A-3. Resistance to noise interference. Q-4. What characteristic of a carrier wave is varied in frequency modulation?

A-4. Instantaneous frequency. Q-5. How is the degree of modulation expressed in an fm system? A-5. As the ratio of the frequency deviation to the maximum frequency deviation allowable. Q-6. What two values may be used to determine the bandwidth of an fm wave? A-6. The number of significant sidebands and the modulating frequency. Q-7. How does the reactance-tube modulator impress intelligence onto an rf carrier? A-7. By changing the reactance of an oscillator circuit in consonance with the modulating voltage. Q-8. What characteristic of a transistor is varied in a semiconductor-reactance modulator?

A-8. Collector-to-emitter capacitance. Q-9. What circuit section is required in the output of a multivibrator modulator to eliminate unwanted output frequencies?

A-9. An LCR filter. Q-10. What characteristic of a varactor is used in an fm modulator?

A-10. Capacitance. Q-11. What type of modulation depends on the carrier-wave phase shift?

A-11. Phase. Q-12. What components may be used to build a basic phase modulator? A-12. A phase-shift network such as a variable resistor and capacitor in series. Q-13. Phase-shift keying is similar to what other two types of modulation?

A-13. Cw and frequency-shift keying. Q-14. Overmodulating an rf carrier in amplitude modulation produces a waveform which is similar to what modulated waveform?

A-14. Pulse modulation.

Q-15. What is prt?

A-15. Pulse-repetition time.

Q-16. What is nonpulse time?

A-16. Rest time.

Q-17. What is average power in a pulsed system? A-17. Peak power during a pulse averaged over pulse time plus rest time. Q-18. What is the primary component for a spark-gap modulator? A-18. Either a fixed spark gap that uses a trigger pulse to ionize the air between the contacts, or a rotary gap that is similar to a mechanical switch.

Q-19. What are the basic components of a thyratron modulator? A-19. Power source, a circuit for storing energy, a circuit for discharging the storage circuit, and a pulse transformer. Q-20. What action is necessary to impress intelligence on the pulse train in pulse modulation?

A-20. Some characteristic of the pulses has to be varied. Q-21. To ensure the accuracy of a transmission, what is the minimum number of times a modulating wave should be sampled in pulse modulation?

A-21. 2.5 times the highest modulating frequency. Q-22. What, if any, noise susceptibility advantage exists for pulse-amplitude modulation over analog amplitude modulation?

A-22. Both are susceptible to noise and interference. Q-23. What characteristics of a pulse can be changed in pulse-time modulation? A-23. The time duration of the pulses or the time of occurrence of the pulses. Q-24. Which edges of the pulse can be modulated in pulse-duration modulation?

A-24. Either, or both at the same time. Q-25. What is the main disadvantage of pulse-position modulation? A-25. It requires synchronization between the transmitter and receiver.

Q-26. What is pulse-frequency modulation? A-26. A method of pulse modulation in which a modulating wave is used to frequency modulate a pulse-generating circuit. Q-27. Pulse-code modulation requires the use of approximations of value that are obtained by what process?

A-27. Quantization. Q-28. If a modulating wave is sampled 10 times per cycle with a 5-element binary code, how many bits of information are required to transmit the signal?

A-28. 50. Q-29. What is the primary advantage of pulse-modulation systems?

A-29. Low susceptibility to noise.

ANTENNAS

Q1. What are the two basic classifications of antennas?

A1. Half-wave (Hertz) and quarter-wave (Marconi).

Q2. What are the three parts of a complete antenna system?

A2. Coupling device, feeder, and antenna. Q3. What three factors determine the type, size, and shape of an antenna? A3. Frequency of operation of the transmitter, amount of power to be radiated, and general direction of the receiving set. Q4. If a wave travels exactly the length of an antenna from one end to the other and back during the period of 1 cycle, what is the length of the antenna?

A4. One-half the wavelength. Q5. What is the term used to identify the points of high current and high voltage on an antenna?

A5. Current and voltage loops. Q6. What is the term used to identify the points of minimum current and minimum voltage on an antenna?

A6. Current and voltage nodes. Q7. The various properties of a transmitting antenna can apply equally to the same antenna when it is used as a receiving antenna. What term is used for this property?

A7. Reciprocity of antennas. Q8. The direction of what field is used to designate the polarization of a wave?

A8. Electric (E) field. Q9. If a wave's electric lines of force rotate through 360 degrees with every cycle of rf energy, what is the polarization of this wave?

A9. Circular polarization. Q10. What type of polarization should be used at medium and low frequencies?

A10. Vertical polarization. Q11. What is an advantage of using horizontal polarization at high frequencies?

A11. Less interference is experienced by man-made noise sources. Q12. What type of polarization should be used if an antenna is mounted on a moving vehicle at frequencies below 50 megahertz?

A12. Vertical polarization. Q13. What is the radiation resistance of a half-wave antenna in free space?

A13. 73 ohms. Q14. A radiating source that radiates energy stronger in one direction than another is known as what type of radiator?

A14. Anisotropic radiator.

NEETS Q&A

Q15. A radiating source that radiates energy equally in all directions is known as what type of radiator?

A15. Isotropic radiator.

Q16. A flashlight is an example of what type of radiator?

A16. Anisotropic radiator. Q17. What terms are often used to describe basic half-wave antennas?

A17. Dipole, doublet and Hertz. Q18. If a basic half-wave antenna is mounted vertically, what type of radiation pattern will be produced?

A18. Nondirectional. Q19. In which plane will the half-wave antenna be operating if it is mounted horizontally?

A19. Vertical plane. Q20. Since the radiation pattern of a dipole is similar to that of a doublet, what will happen to the pattern if the length of the doublet is increased?

A20. The pattern would flatten. Q21. What is the simplest method of feeding power to the half-wave antenna? A21. To connect one end through a capacitor to the final output stage of the transmitter.

Q22. What is the radiation pattern of a quarter-wave antenna? A22. A circular radiation pattern in the horizontal plane, or same as a half wave.

Q23. Describe the physical arrangement of a ground screen. A23. It is composed of a series of conductors arranged in a radial pattern and buried 1 to 2 feet below the ground. Q24. What is the difference in the amount of impedance between a three-wire dipole and a simple center-fed dipole?

A24. Nine times the feed-point impedance. Q25. Which has a wider frequency range, a simple dipole or a folded dipole?

A25. Folded dipole.

Q26. What is the purpose of antenna stubs? A26. To produce desired phase relationship between connected elements. Q27. What is the primary difference between the major and minor lobes of a radiation pattern?

A27. Major lobes have the greatest amount of radiation. Q28. What is the maximum number of elements ordinarily used in a collinear array?

A28. Four. Q29. Why is the number of elements used in a collinear array limited? A29. As more elements are added, an unbalanced condition in the system occurs which impairs efficiency. Q30. How can the frequency range of a collinear array be increased?

A30. By increasing the lengths of the elements of the array. Q31. How is directivity of a collinear array affected when the number of elements is increased?

A31. Directivity increases. Q32. What is the primary cause of broadside arrays losing efficiency when not operating at their designed frequency?

A32. Lower radiation resistance. Q33. When more than two elements are used in a broadside array, how are the elements arranged?

A33. Parallel and in the same plane. Q34. As the spacing between elements in a broadside array increases, what is the effect on the major lobes?

A34. They sharpen.

Q35. What are some disadvantages of the end-fire array? A35. Extremely low radiation resistance, confined to one frequency, and affected by atmospheric conditions.

Q36. Where does the major lobe in the end-fire array occur?

A36. Along the major axis Q37. To maintain the required balance of phase relationships and critical feeding, how must the end-fire array be constructed?

A37. Symmetrically. Q38. What two factors determine the directivity pattern of the parasitic array? A38. Length of the parasitic element (tuning) and spacing between the parasitic and driven elements. Q39. What two main advantages of a parasitic array can be obtained by combining a reflector and a director with the driven element?

A39. Increased gain and directivity. Q40. The parasitic array can be rotated to receive or transmit in different directions. What is the name given to such an antenna?

A40. Rotary array.

Q41. What are the disadvantages of the parasitic array? A41. Their adjustment is critical and they do not operate over a wide frequency range. Q42. What is the advantage of adding parasitic elements to a Yagi array?

A42. Increased gain.

Q43. The Yagi antenna is an example of what type of array?

A43. Multielement parasitic array. Q44. To radiate power efficiently, a long-wire antenna must have what minimum overall length?

A44. One-half wavelength.

Q45. What is another name for the Beverage antenna?

A45. Wave antenna.

Q46. What is the polarity of the currents that feed the V antenna?

A46. Opposite.

Q47. What is the main disadvantage of the rhombic antenna?

A47. It requires a large antenna site. Q48. What is the primary reason for the development of the turnstile antenna?

A48. For omnidirectional vhf communications.

BACKGROUND ON FIBER OPTICS

Q1. Define fiber optics. A1. Fiber optics is the branch of optical technology concerned with the transmission of radiant power (light energy) through fibers.

Q2. Describe the basic functions of a fiber optic data link. A2. The basic functions of a fiber optic data link are to convert an electrical input signal to an optical signal, send the optical signal over an optical fiber, and convert the optical signal back to an electrical signal.

Q3. List the three parts of a fiber optic data link.

A3. Transmitter, optical fiber, and receiver. Q4. What mechanisms in the fiber waveguides weaken and distort the optical signal?

A4. Scattering, absorption, and dispersion.

Q5. What effect does noise have on the fiber optic signal?

A5. Noise obscures or reduces the quality of the signal.

Q6. Define loss. A6. Loss is the decrease in the amount of light reaching the end of the fiber. Q7. In 1969, what did several scientists conclude about optical fiber loss? A7. Impurities in the fiber material caused the signal loss in optical fibers. The basic fiber material did not prevent the light signal from reaching the end of the fiber. Q8. How can loss be reduced during construction (or fabrication) of optical fibers?

A8. By removing the impurities from optical fiber.

Q9. What are the two basic types of optical fibers?

A9. Multimode and single mode fibers. Q10. Which type of optical fiber (multimode or single mode) tends to have lower loss and produces less signal distortion?

A10. Single mode fiber. Q11. What optical fiber properties reduce connection loss in short-distance systems?

A11. Larger fiber core and higher fiber numerical aperture (NA).

Q12. In fiber optic systems, designers consider what trade-offs? A12. Trade-offs in fiber properties, types of connections, optical sources, and detector types in military and subscriber-loop applications. Q13. List seven advantages of fiber optics over electrical systems. A13. Advantages of fiber optics are improved system performance, immunity to electrical noise, signal security, electrical isolation, reduced size and weight, environmental protection, and overall system economy.

BASIC MEASUREMENTS

Q-1. What assures the accuracy of your electronic test equipment?

A-1. Its calibration. Q-2. The input impedance of your test equipment should exceed the impedance of the circuit under test by what ratio?

A-2. 10 to 1

Q-3. What are the advantages of using two voltmeters in series? A-3. Increased input impedance, greater accuracy, and increased voltage range.

NEETS Q&A

Q-4. At what point on a meter movement are the most accurate readings taken?

A-4. Midscale.

Q-5. What are the advantages of using a differential voltmeter?

A-5. Accuracy and high input impedance. Q-6. The frequency response of test equipment refers to what aspect of ac voltage measurements?

A-6. The range of frequencies that can accurately be measured. Q-7. Ideally, an oscilloscope presentation should cover what vertical portion of the screen?

A-7. At least 60% of the vertical trace. Q-8. What are the advantages of connecting ammeters in parallel when performing current measurements? A-8. Decreased internal meter resistance, greater accuracy, and greater current range.

Q-9. What is the primary advantage of using a current probe? A-9. Current probes enable you to perform current measurements without disconnecting wires. Current probes are clamped around the insulated wire. Q-10. How do you compensate for the resistance of the test leads of a meter?

A-10. By zeroing the meter with the test leads shorted. Q-11. Why are digital multimeters well suited for testing sensitive devices?

A-11. The current flow through the component is limited to 1 milliamp.

Q-12. Charged capacitors can kill. True or false?

A-12. True. Q-13. Which is more accurate, the bridge- or reactance-type meter?

A-13. Bridge type.

Q-14. What type of core produces the greatest inductance?

A-14. Magnetic-metal core. Q-15. A Hay bridge measures inductance by comparing an inductor to what component?

A-15. A capacitor. Q-16. Is the current flow through an inductor directly proportional or inversely proportional to its inductance value?

A-16. Directly proportional.

BASIC METERS

Q-1. What meters operate from their own power sources?

A-1. Self-excited. Q-2. What physical component of a galvanometer provides the restoring force for the coil?

A-2. Phosphor bronze ribbons. Q-3. In a galvanometer, what two methods are used to indicate the amount of coil rotation?

A-3. The pointer arrangement and the light and mirror arrangement. Q-4. What is the primary disadvantage of the pointer arrangement for indicating coil rotation?

A-4. Coil balance. Q-5. What component of the D’Arsonval meter movement completes the circuit for current flow to the coil?

A-5. Hairspring. Q-6. What component supplies restoring force to the coil of the D’Arsonval meter movement?

A-6. Hairspring. Q-7. What advantage is gained by using pole pieces with curved faces in the D’Arsonval meter movement? A-7. Makes it possible to have a more linear scale than if the poles were flat. Q-8. What structurally large, low-resistance conductor is connected in parallel with the meter movement to prevent damage?

A-8. Shunt. Q-9. What type of temperature coefficient material does not produce increased heat in response to increased current flow?

A-9. Zero-temperature coefficient. Q-10. A good choice of shunt resistance will place the indicating pointer near what part of the meter scale with a normal load?

A-10. Midscale. Q-11. In what manner are current-measuring instruments connected to a circuit?

A-11. In series. Q-12. An ammeter should always be connected so that current will flow into what terminal and out of what terminal?

A-12. Negative, positive. Q-13. (True or False) The larger the current required to produce full-scale deflection of the meter coil, the better the sensitivity of

the meter.

A-13. False. Q-14. What condition exists when the insertion of a meter into a circuit changes the operation of the circuit?

A-14. Meter-loading. Q-15. What modification is made to the D’Arsonval meter movement to enable the meter to measure voltage? A-15. A multimeter (high resistance) is placed in series with the coil of the meter.

Q-16. What factors determine the value of the multiplier resistor? A-16. The current required for full-scale deflection, and the range of the voltage to be measured. Q-17. In what manner are voltage-measuring instruments connected to the circuit to be measured?

A-17. In parallel. Q-18. When making voltage measurements in a high-resistance circuit, you should always use a voltmeter with what relative value of resistance?

A-18. High. Q-19. What term is used to express the sensitivity of a voltmeter?

A-19. Ohms per volt. Q-20. What instrument is used for measuring the insulation resistance of cables?

A-20. Megohmmeter (megger). Q-21. What added features enable a dc milliammeter to function as an ohmmeter? A-21. 1. A source of dc potential. 2. One or more resistors (one of which is variable). Q-22. A full-scale deflection on an ohmmeter scale indicates what resistance between the leads?

A-22. Zero. Q-23. The R x 100 resistance selection on an ohmmeter has what amount of resistance compared to the R x 10 selection?

A-23. 1/10.

Q-24. What is the purpose of the guard ring in a megohmmeter?

A-24. Shunts leakage current, which prevents false readings.

Q-25. Most meggers you will use are rated at what voltage?

A-25. 500. Q-26. The development of excessive test voltages is avoided by the use of meggers equipped with what device?

A-26. Friction clutches. Q-27. What components in an electrodynamometer-type meter movement produce the magnetic field?

A-27. Fixed coils. Q-28. What is the limiting factor as to the amount of current an electrodynamometer meter movement can handle?

A-28. Size of spiral conducting. Q-29. What is the primary advantage of the electrodynamometer-type meter over the D’Arsonval-type meter? A-29. The electrodynamometer-type meter can be used to measure both ac and dc currents.

BATTERIES

Q1. What is the purpose of a cell? A1.A cell is a device that converts chemical energy to electrical energy.

Q2. What are the three parts of a cell?

A2.The electrodes, the electrolyte, and the container.

Q3. What is the purpose of each of the three parts of a cell? A3.The electrodes are the current conductors of the cell. The electrolyte is the solution that acts upon the electrodes. The container holds the electrolyte and provides a means of mounting the electrodes.

Q4. What are the two types of cells?

A4.Primary and secondary.

Q5. What is the main difference between the two types of cells? A5.The secondary cell can be restored to its original condition by an electric current. The primary cell cannot.

Q6. What is electrochemical action?

A6.The process of converting chemical energy into electrical energy. Q7. What is another name for the (a) positive electrode, and the (b) negative electrode?

A7.(a) The anode, (b) the cathode. Q8. In the primary cell, why are negative ions attracted to the negative terminal of the cell? A8.The positive charge caused by electrons leaving the negative electrode attracts the negative ions.

Q9. How do electrons get from the negative electrode to the

NEETS Q&A

positive electrode?

A9.By current flow through the load.

Q10. What causes the negative electrode to be eaten away? A10.The chemical action between the negative electrode and the electrolyte.

Q11. Refer to figure 2-3(B). Why is the sulfuric acid decreasing? A11.The sulfuric acid is chemically acting upon the anode and cathode which creates a current flow through the load. Q12. Refer to figure 2-3(D). How is it possible for the sulfuric acid to be increasing? A12.The charging currents causes the lead sulfate in the anode and cathode to be changed back to lead peroxide, sponge lead, and sulfuric acid. Q13. Refer to figure 2-3(D). When all the lead sulfate has been converted, what is the condition of the cell?

A13.Fully charged.

Q14. Describe three ways to prevent polarization. A14.Vent the cell, add a material rich in oxygen, and use a material that will absorb hydrogen.

Q15. Describe local action

A15.Current flow in a cell with no external load.

Q16. What serves as the cathode of a dry cell?

A16.The zinc container.

Q17. Why is a dry cell called a DRY cell?

A17.The electrolyte is not a liquid but is in the form of a paste.

Q18. What does the term "shelf life" mean?

A18.The period that a cell can be stored and still be useable.

Q19. Why should a mercury cell NOT be shorted?

A19.The danger of explosion. Q20. What factors should be considered when selecting a primary cell for a power source?

A20.Cost, size, ease of replacement, and voltage or current needs.

Q21. What are the four basic types of secondary (wet) cells? A21.Lead-acid, nickel-cadmium (NICAD), silver-zinc, and silver-cadmium. Q22. What are the advantages of a nicad cell over a lead-acid cell? A22.Can be charged in a shorter time, can deliver a larger amount of power, and stays idle longer. Q23. What type of cell is most commonly used for emergency systems?

A23.Silver-zinc cell.

Q24. What three cells use the same electrolyte?

A24.Silver-cadmium, silver-zinc, and nickel-cadmium.

Q25. What does the term battery normally refer to? A25.A voltage source in a single container made from one or more cells. Q26. What are the three ways of combining cells, and what is each used for? A26.Series, to increase voltage but not current. Parallel, to increase current but not voltage. Series-Parallel, to increase both current and voltage. Q27. Other than the type of cell used, what is the major difference between the construction of the leadacid and nicad battery?

A27.The cells in the nicad battery can be replaced.

Q28. How is the type of battery most easily determined?

A28.By looking at the nameplate data.

Q29. What is the purpose of the hydrometer?

A29.To measure the amount of active ingredient in the electrolyte. Q30. Which electrolyte has more active ingredient? Electrolyte A, specific gravity 1.015? Electrolyte B, specific gravity 1.125?

A30.Electrolyte B. It is heavier per unit volume. Q31. When should safety precautions pertaining to batteries be observed?

A31.At all times. Q32. How long should a 200 ampere-hour battery be able to deliver 5 amperes?

A32.Forty hours.

Q33. Can a battery be recharged by adding more electrolytes?

A33.No, a current must be passed through the battery. Q34. If violent gassing occurs during a battery charge, what action should be taken?

A34.Reduce the charging rate.

CAPACITANCE

Q1. Define the terms "capacitor" and "capacitance." A1. a. A capacitor is a device that stores electrical energy in an electrostatic field. b. Capacitance is the property of a circuit which opposes changes in voltage.

Q2. State four characteristics of electrostatic lines of force. A2. a. They are polarized from positive to negative. b. They radiate from a charged particle in straight lines and do not form closed loops. c. They have the ability to pass through any known material. d. They have the ability to distort the orbits of electrons circling the nucleus. Q3. An electron moves into the electrostatic field between a positive charge and a negative charge. Toward which charge will the electron move?

A3. Toward the positive charge.

Q4. What are the basic parts of a capacitor?

A4. Two pieces of conducting material separated by an insulator.

Q5. Define the term "farad." A5. A farad is the unit of capacitance. A capacitor has a capacitance of 1 farad when a difference of 1 volt will charge it with 1 coulomb of electrons. Q6. What is the mathematical relationship between a farad, a microfarad, and a picofarad. A6. a. One microfarad equals 10-6 farad. b. One picofarad equals 10-12 farad.

Q7. State three factors that affect the capacitance of a capacitor. A7. a. The area of the plates. b. The distance between the plates. c. The dielectric constant of the material between the plates. Q8. A parallel plate capacitor has the following values: K = 81, d = .025 inches, A = 6 square inches. What is the capacitance of the capacitor?

A8. 4372 picofarads 0.025

6810.2249 C

d

KA0.2249 C

×== = 4372

picofarads (round off)

Q9. Name two types of power losses associated with a capacitor. A9. a. Hysteresis b. Dielectric leakage Q10. a. Define the term "working voltage" of a capacitor. b. What should be the working voltage of a capacitor in a circuit that is operating at 600 volts? A10. a. It is the maximum voltage the capacitor can work without risk of damage. b. 900 volts. Q11. State what happens to the electrons in a capacitor circuit when (a) the capacitor is charging and (b) the capacitor is discharging. A11. a. When the capacitor is charging, electrons accumulate on the negative plate and leave the positive plate until the charge on the capacitor is equal to the battery voltage. b. When the capacitor is discharging, electrons flow from the negatively charged plate to the positively charged plate until the charge on each plate is neutral. Q12. At what instant does the greatest voltage appear across the resistor in a series RC circuit when the capacitor is charging?

A12. At the instant of the initiation of the action. Q13. What is the voltage drop across the resistor in an RC charging circuit when the charge on the capacitor is equal to the battery voltage?

A13. Zero. Q14. What is the RC time constant of a series RC circuit that contains a 12-megohm resistor and a 12-microfarad capacitor?

A14.144 seconds (t=R x C) Q15. A circuit is to be designed in which a capacitor must charge to 40 percent of the maximum charging voltage in 200 microseconds. The resistor to be used has a resistance of 40,000 ohms. What size capacitor must be used?

A15. 0.1 microfarads 40% from the graph = 0.5 Q16. What is the total capacitance of a circuit that contains two capacitors (10 µF and 0.1 µF) wired together in series?

A16. 0.1microfarads

2C

1C

2C

1C

T

C+

=

Q17. What is the total capacitance of a circuit in which four capacitors (10 µF, 21 µF, 0.1 µF and 2 µF) are connected in parallel?

A17. 33.1µF CT = C1 + C2 + C3 + C4

Q18. a. An oxide-film dielectric is used in what type of capacitor? b. A screw adjustment is used to vary the distance

NEETS Q&A

between the plates of what type of capacitor?

A18. a. Electrolytic capacitor b. Trimmer capacitor

Q19. Examine the three capacitors shown below. What is the capacitance of each? A19. a. 26µF or 260,00pF b. 630pF c. 9600pF

CIRCUIT CONTROL DEVICES

Q1. What are three reasons circuit control is needed? A1. To remove power from a malfunctioning device; to remove power from a device you wish to work on and restore power when the work is completed; to turn devices on and off as the device is needed; to select the function or circuit desired within a device.

Q2. What are the three types of circuit control devices?

A2. Switches, solenoids, and relays. Q3. Label the schematic symbols shown in figure 3-2.

a. Solenoid. b. Switch. c. Relay.

Q4. What is the difference between a manual and an automatic switch? A4. A manual switch must be turned on or off by a person. An automatic switch turns a circuit on or off without the action of a person (by using mechanical or electrical devices).

Q5. What is one example of a manual switch?

A5. A light switch, an ignition switch, television channel selector, etc.

Q6. What is one example of an automatic switch?

A6. A thermostat, an automobile distributor, a limit switch, etc.

Q7. Why are multicontact switches used? A7. Multicontact switches make possible the control of more than one circuit or the selection of one of several possible circuits with a single switch. Q8. Label the schematic symbols shown in figure 3-4 as to number of poles and number of throws.

a. Three-pole, single-throw (triple-pole, single-throw)

b. Double-pole, double-throw

c. Single-pole, double-throw

d. Single-pole, single-throw

e. Double-pole, triple-throw

f. Six-pole, double-throw Q9. Label the switch schematics shown in figure 3-10A through 3-10G.

a. Single-pole, single-throw, single-break

b. Single-pole, double-throw, single-break

c. Single-pole, single-throw, double-break

d. Single-pole, double-throw, double-break

e. Rotary

f. Wafer

g. Double-pole, double-throw, double-break Q10. What classification of a switch is used when you describe it as a rocker switch?

A10. The type of actuator.

Q11. In describing a switch by the number of positions of the actuator, what are the two possible configurations for a single-pole, double-throw switch?

A11. Two-position and three-position. Q12. What type of switch should be used to control a circuit that requires a temporary actuation signal?

A12. A momentary switch. Q13. What type of switch is used if it is necessary to guard against a circuit being accidentally turned

A13. A locked-position switch. Q14. What is the common name used for an accurate snap-acting switch?

A14. A microswitch.

Q15. What is the current rating of a switch?

A15. The maximum current a switch is designed to carry.

Q16. What is the voltage rating of a switch? A16. The maximum voltage allowable in the circuit in which the switch is installed.

Q17. What two types of meters can be used to check a switch?

A17. An ohmmeter and a voltmeter. Q18. If a switch must be checked with power applied, what type of meter is used?

A18. A voltmeter. Q19. A double-pole, double-throw, single-break, three-position, toggle switch is faulty. This switch has a momentary position 1 and is locked out opposition 3. The voltage and current ratings for the switch are 115 volt dc, 5 amperes. No direct replacement is available. From switches A through I, in table 3-1, indicate if the switch is acceptable or not acceptable as a substitute. Of the

A19.

a. Not acceptable-single throw.

b. Not acceptable-double break.

c. Acceptable-choice #2 (different actuator).

d. Not acceptable-single pole.

e. Not acceptable-no momentary position.

f. Acceptable-choice #1 (higher rating).

g. Not acceptable-locked position incorrect.

h. Not acceptable-current rating too low.

i. Not acceptable-voltage rating too low. Q20. What should you check when performing preventive maintenance on a switch? A20. The switch operation for smooth and correct operation, the terminals for corrosion, and the physical condition of the switch.

Q21. What is the operating principle of a solenoid? A21. The magnetic field created in a coil of wire and core will attract a soft iron plunger when current flows through the coil.

Q22. What is one example of the use of a solenoid?

A22. A starter motor and solenoid. Q23. If a solenoid is not operating properly, what items should be checked? A23. The connections, the plunger, the mechanism that the solenoid actuates, the energizing voltage, and the coil of the solenoid.

Q24. What is the operating principle of a relay? A24. The magnetic field created in a coil of wire will attract aft armature causing a movement in sets of contacts.

Q25. How does a relay differ from a solenoid? A25. The solenoid provides a mechanical movement of a plunger (a moveable core) while the core of a relay is fixed.

Q26. What are the two classifications of relays?

A26. Control relays and power relays (contactors).

Q27. How can you determine if a relay is operating (changing from one position to the other)? A27. By observing the movement of the contacts if the relay is open or sealed with a transparent cover. If the relay has an opaque cover, you can "feel" the operation of the relay by placing your finger on the cover.

Q28. What items should be checked on a relay that is not operating properly? A28. The coil should be checked for opens, shorts, or a short to ground; terminal leads should be checked for charred or burned

NEETS Q&A

insulation; the contact surfaces should be checked for film, carbon, arcing, and contact spacing.

Q29. What is used to clean the contacts of a relay?

A29. A burnishing tool.

Q30. What tool is used to set contact clearances on a relay?

A30. A point bender

CIRCUIT MEASUREMENT

Q1. What are two ways that circuit measurement is used? A1. Circuit measurement is used to (1) monitor the operation of a piece of electrical or electronic equipment and (2) determine the reason a piece of electrical or electronic equipment is not functioning properly.

Q2. Why is in-circuit meters used? A2. In-circuit meters are used to monitor the operation of electrical or electronic devices.

Q3. What is one advantage of an out-of-circuit meter when it is compared with an in-circuit meter? A3. Out-of-circuit meters can be used on more than one electrical or electronic device. Q4. How does a compass react when placed close to a current carrying conductor? A4. The compass needle swings away from magnetic north and aligns itself with the magnetic field around the conductor Q5. If the amount of current in the conductor changes, what happens to the magnetic field around the conductor? A5. If the current increases the magnetic field increases; if the current decreases the magnetic field decreases.

Q6. How does the compass needle react to a decreased magnetic field? A6. The compass needle will not be deflected as far from magnetic north. Q7. What type of meter movement is the d’Arsonval meter movement? A7. A permanent-magnet moving-coil meter movement used in most electrical and electronic meters. Q8. What is the effect of current flow through the coil in a d’Arsonval meter movement? A8. A magnetic field is generated around the coil and the attraction of this field with the permanent magnet causes the coil to move.

Q9. What are three functions of the hairsprings in a d’Arsonval meter movement? A9. To return the pointer to its rest position when there is no current flow; to oppose the coil movement when there is current flow; to provide electrical connections for the coil. Q10. How would a compass react when placed close to a conductor carrying alternating current at a low frequency? A10. The compass needle would swing back and forth as the current changed from positive to negative.

Q11. How would the compass react if the alternating current through the conductor was a high frequency? A11. The compass needle would vibrate rapidly around the zero-current point ac meter (magnetic north).

Q12. What is the purpose of a rectifier in a meter? A12. A rectifier changes alternating current to pulsating direct current and allows a dc meter to measure ac.

Q13. How can a d’Arsonval meter movement be adapted for use as an ac meter? A13. By the use of a rectifier

Q14. What is damping? A14. The process of "smoothing out" the oscillation in a meter movement.

Q15. What are two methods used to damp a meter movement? A15. As the coil moves through the field of the permanent magnet, a current is induced in the coil opposing the movement of the coil; and a vane can be attached to the coil and placed in the airtight chamber so that the movement of the vane opposes the movement of the coil.

Q16. What value does a meter movement react to (actually measure) when measuring ac? A16. Average value.

Q17. What value is indicated on the scale of an ac meter?

A17. Effective value (rms).

Q18. List three meter movements that can measure either ac or dc without the use of a rectifier. A18. Electrodynamic, moving vane, and hot-wire or thermocouple.

Q19. What electrical property is used by all the meter movements discussed so far? A19. Current.

Q20. What electrical property does an ammeter measure?

A20. Current.

Q21. How is an ammeter connected to the circuit under test?

A21. In series.

Q22. How does an ammeter affect the circuit being measured? A22. Since the ammeter is a resistor in series with the load, it increases the resistance of the circuit and lowers circuit current.

Q23. How the ammeter’s effect on the circuit being measured is kept to a minimum? A23. The resistance of the ammeter must be much smaller than the circuit load.

Q24. What is ammeter sensitivity?

A24. The amount of current that will cause full-scale deflection.

Q25. What is used to allow an ammeter to measure different ranges? A25. Shunt resistors (internal or external).

Q26. Why should you use the highest range of an ammeter for the initial measurement? A26. To prevent damage to the meter movement from excessive current. Q27. What range of an ammeter is selected for the final measurement? A27. A range that allows a meter reading near the center of the scale.

Q28. List the six safety precautions for the use of ammeters. A28. a. Always connect an ammeter in series. b. Always start with the highest range. c. In dc ammeters, observe the proper polarity. d. Deenergize and discharge the circuit before connecting or disconnecting the ammeter. e. Never use a dc ammeter to measure ac current. f. Observe the general safety precautions of electric and electronic devices. Q29. Why will an ammeter be damaged if connected in parallel with the circuit to be measured? A29. Since the ammeter has a small resistance compared to the load, it will have very high current if it is connected in parallel. This high current will damage the meter.

Q30. What electrical quantity is measured by a voltmeter?

A30. Voltage.

Q31. How is a voltmeter connected to the circuit to be measured? A31. In parallel.

Q32. What is the loading effect of a voltmeter? A32. The connection of a voltmeter adds a resistance in parallel with the circuit changing the total circuit resistance, and loads the circuit.

Q33. How is the loading effect of a voltmeter kept to a minimum? A33. A voltmeter must have a high resistance compared to the circuit being measured. Q34. How is it possible to use a current sensitive meter movement to measure voltage? A34. Since the resistance of a meter movement remains the same as the pointer is deflected, the amount of current through the movement is proportional to the voltage applied. Therefore, only the scale of the movement must be changed.

Q35. What is voltmeter sensitivity? A35. It is an indication of the resistance of the meter expressed in ohms per volt. The total resistance of the meter is the sensitivity multiplied by the full-scale voltage. Q36. What method is used to allow a voltmeter to have several ranges? A36. The use of resistors in series with the meter movement.

Q37. Why should you always use the highest range when connecting a voltmeter to a circuit? A37. To prevent excess current through the meter movement.

Q38. What type of meter movement reacts to voltage rather than current? A38. Electrostatic.

Q39. What is the only use for the voltage sensitive meter movement? A39. High-voltage measurement.

Q40. List the six safety precautions for the use of voltmeters. A40. a. Always connect a voltmeter in parallel. b. Always start with the highest range. c. Deenergize and discharge the circuit before connecting or disconnecting the voltmeter. d. In a dc voltmeter, observe the proper polarity. e. Never use a dc voltmeter to measure ac voltage. f. Observe the general safety precautions of electric and electronic devices.

Q41. What electrical quantity is measured by an ohmmeter?

A41. Resistance.

Q42. What other measurement can an ohmmeter make?

A42. Circuit continuity.

Q43. How is a series-type ohmmeter connected to the circuit being measured?

NEETS Q&A

A43. The ohmmeter is connected in series with the resistance to be measured.

Q44. What is used to provide the ohmmeter with several ranges? A44. An ohmmeter has several internal range resistors and a switch or a series of jacks to select the proper range.

Q45. What area of an ohmmeter scale should be used when measuring circuits? A45. The middle of the scale.

Q46. What are the two types of ohmmeters?

A46. Series and shunt.

Q47. What is the most obvious difference between the two types of ohmmeters? A47. Series ohmmeters have 0 on the right end of the scale and ¥ on the left end of the scale. Shunt ohmmeters are the opposite. Q48. List the four safety precautions observed when using ohmmeters. A48. a. Deenergize and discharge the circuit before connecting an ohmmeter. b. Do not apply power to a circuit while measuring resistance. c. Switch ohmmeters to the OFF position, if provided, or to highest range and remove meter leads from the meter when finished measuring resistance. d. Adjust the ohmmeter after changing resistance range and before measuring reading indicates the resistance.

Q49. What is the primary use of a megger?

A49. To measure high resistance.

Q50. What is the procedure for using a megger to check the insulation of a conductor? A50. Connect one lead to the insulation and one lead to the conductor. Turn the handcrank until it starts to slip. Note the reading. Q51. What is a normal indication on a megger when checking insulation? A51. Infinity.

Q52. List the four safety precautions observed when using a megger. A52. a. Use meggers for high-resistance measurement only. b. Never touch the test leads when the handle is being cranked. c. Deenergize and discharge the circuit completely before connecting a megger. d. Disconnect the item being checked from other circuitry, if possible, before using a megger.

Q53. What is a multimeter? A53. A single measuring device capable of performing the functions of a dc voltmeter and ammeter, an ac voltmeter and ammeter, and an ohmmeter.

Q54. Why is a multimeter preferred over separate meters? A54. It is much more convenient to have one meter with several functions than several meters each with a single function.

Q55. How is a multimeter changed from a voltage measuring device to a resistance measuring device? A55. By changing the position of the function switch.

Q56. Why is the dc scale on a multimeter different than the ac scale? A56. The meter movement reacts to average ac voltage and current and the effective value is desired.

Q57. What is the reason for having a mirror on the scale of a multimeter? A57. To stop parallax error

Q58. How is the mirror on a multimeter used? A58. Make sure no image of the pointer is visible in the mirror when reading the meter.

Q59. List the 11 safety precautions for multimeters. A59. a. Deenergize and discharge the circuit completely before connecting or disconnecting a multimeter. b. Never apply power to the circuit while measuring resistance with a multimeter. c. Connect the multimeter in series with the circuit for current measurements, and in parallel for voltage measurements. d. Be certain the multimeter is switched to ac before attempting to measure ac circuits. e. Observe proper dc polarity when measuring dc. f. When you are finished with a multimeter, switch it to the OFF position, if available. If there is no OFF position, switch the multimeter to the highest ac voltage position. g. Always start with the highest voltage or current range. h. Select a final range that allows a reading near the middle of the scale. i. Adjust the "0 ohms" reading after changing resistance ranges and before making a resistance measurement. j. Be certain to read ac measurements on the ac scale of a multimeter. k. Observe the general safety precautions for electrical and

electronic devices.

Q60. Why would you use a hook-on voltmeter instead of a multimeter? A60. To measure current safely and easily (with no need to disconnect the wiring of the circuit).

Q61. What electrical quantity is measured by a wattmeter?

A61. Power.

Q62. What electrical quantity is measured by a watt-hour meter?

A62. Energy.

Q63. What is the quantity shown on the watt-hour meter in figure 1-46? A63. 5.945 megawatt-hours, or 5,945 kilowatt-hours, or 5,945, 000 watt-hours.

Q64. What are two types of frequency meters?

A64. Vibrating reed and moving disk.

Q65. What type of meter is shown and what is the value of the quantity being measured for each meter in figure1-49? A65. a. A dc ammeter, 90 mA dc b. A dc voltmeter, 200 V dc c. An ac voltmeter, 4.6 V ac d. An ohmmeter, 400 ohms Q66. What meter reading is shown on each multimeter in each part of figure 1-50? A66. (A) 410 mA dc; (B) 3.9 mA ac; (C) -22 V dc; (D) 600 V ac; (E) 1.4 V ac; (F) 1.9 kohms

Q67. Which part of figure1-50 shows the switch positions the multimeter should be left in when the meter is secured?

A67. Q68. What type of meter is shown and what is the value of the quantity being measured for each meter in figure 1-51? A68. (A) Megger (megohmmeter), infinity; (B) Wattmeter, 9.5 kilowatts (9,500 watts). (C) Watt-hour meter, 2.693 megawatt-hours 2,693 kilowatt-hours) (2,693,000 watt-hours). Q69. If the insulation of a conductor was being measured in figure1-51 (A), would the reading indicate a good insulation? A69. Yes.

Q70. What type of frequency meter is shown and what is the value indicated for each meter in figure 1-52? A70. (A) Vibrating-reed, 60Hz. (B) Moving-disk, 58 Hz.

CIRCUIT PROTECTION DEVICES

Q1. Why are circuit protection devices necessary? A1. To protect people and circuits from possible hazardous conditions.

Q2. What are the three conditions that require circuit protection?

A2. A direct short, excessive current and excessive heat.

Q3. What is a direct short? A3. A condition in which some point in the circuit where full system voltage is present comes in contact with the ground or return side of the circuit.

Q4. What is an excessive current condition? A4. A condition that is not a direct short but in which circuit current increases beyond the designed current carrying ability of the circuit.

Q5. What is an excessive heat condition? A5. A condition in which the heat in or around the circuit increases to a higher than normal level

Q6. How are circuits protections devices connected to the circuit they are intended to protect and why are they connected in this way?

A6. In series, so total current will be stopped when the device opens.

Q7. What are the two types of circuit protection devices?

A7. Fuses and circuit breakers. Q8. Label the schematic symbols shown in figure 2-3 below.

a. circuit breaker b. Fuse.

Q9. Label the fuses shown in figure 2-6 according to type.

NEETS Q&A

a. cartridge b. plug c. plug d. cartridge.

Q10. Identify the open fuses shown in figure 2-6.

A10. A, C.

Q11. In what three ways are fuses rated?

A11. Current, voltage, and time delay.

Q12. What does the current rating of a fuse indicate?

A12. The amount of current the fuse will allow without opening.

Q13. What does the voltage rating of a fuse indicate? A13. The ability of the fuse to quickly extinguish the arc after the fuse element melts and the maximum voltage that cannot jump across the gap of the fuse after the fuse opens.

Q14. What are the three time delay ratings of fuses?

A14. Delay, standard, and fast.

Q15. Give an example of a device you could protect with each type of time delay fuse. A15. Delay-Motors, solenoids, or transformers. Standard-Automobiles, lighting or electrical power circuits. Fast-Delicate instruments or semiconductor devices. Q16. What are the voltage, current, and time delay ratings for a fuse with the designation

A16.

a. 125 volts or less, 1.5 amperes, delay

b. 250 volts or less, 1/8 ampere standard Q17. What are the voltage and current ratings for a fuse designated

A17.

a. 125 volts or less, 1/16 ampere

b. 250 volts or less, .15 ampere

Q18. What is the new military designation for a fuse with the old military designation F05A20ROB?

A18. F05B32V20A.

Q19. Label the fuseholders in figure 2-12.

a. Post-type fuseholder b. Clip-type fuseholder

Q20. Which connector should you use to connect the (a) power source and (b) load to the fuseholder shown in figure 2-12(A)?

a. Center connector b. Outside connector

Q21. What are three methods for determining if a fuse is open?

A21. Visual inspection, indicators, and using a meter.

Q22. You have just checked a fuse with an ohmmeter and find that the fuse is shorted. What should you A22. Put it back in the circuit. A good fuse will have zero ohms of resistance. Q23. You have just checked a 1/500-ampere fuse with an ohmmeter and find it is open. Checking the replacement fuse shows the replacement fuse is open also. Why would the replacement fuse indicate open? A23. The ohmmeter causes more than 1/500 ampere through the fuse when you check the fuse, thus it opens the fuse. Q24. How could you check a 1/500-ampere fuse with an ohmmeter? A24. Use a resistor in series with the fuse when you check it with the ohmmeter. Q25. List the safety precautions to be observed when checking fuses. A25. Turn the power off and discharge the circuit before you remove fuses. Use a fuse puller (an insulated tool) when you remove fuses

front clip-type fuse holders. When you check fuses with a voltmeter, be careful to avoid shocks and short circuits.

Q26. You have removed an open fuse from a fuseholder and repaired the cause of the fuse opening. The parts list specifies a fuse coded F02BI25VñA. There are no fuses available with that identification. In the following list, indicate if the fuse is a direct replacement, a good substitute, or not acceptable. For the fuses that are good substitutes, number them in order of preference and explain why they are numbered that way. If the fuse is not acceptable, explain why.

(a) F03BI25V½A

(b) F02BI25V3/8A

(c) F02GR500B

(d) F02B32V½A

(e) F02DR500B

(f) F02A250V5/8A

(g) F02AI25V½A

A26.

a. Not acceptable-wrong style

b. Substitute #3-smaller current rating

c. Substitute #1-identical, except higher voltage rating

d. Not acceptable-lower voltage rating

e. Direct replacement

f. Not acceptable-higher current rating

g. Substitute #2-Faster time delay rating

Q27. What two things should you check before replacing a fuse?

A27. Check for the proper type of replacement fuse and proper fit. Q28. List the safety precautions to be observed when replacing a fuse. A28. Be sure the power is off in the circuit and the circuit is discharged before replacing a fuse. Use an identical replacement fuse if possible. Remove any corrosion from the fuseholders before replacing the fuses. Q29. What conditions should you check for when conducting preventive maintenance on fuses?

A29. Improper fuse, corrosion, improper fit, and open fuse.

Q30. What are the five main components of a circuit breaker? A30. Frame, operating mechanism, arc extinguishers, terminal connectors, and trip element.

Q31. What are the three types of circuit breaker trip elements?

A31. Thermal, magnetic, and thermal-magnetic.

Q32. How does each type of trip element react to an overload? A32. The thermal trip element makes use of a bimetallic element that bends with an increase in temperature or current. The bending causes the trip bar to be moved releasing the latch.

Q33. What is a trip-free circuit breaker? A33. A circuit breaker that will trip even if the operating mechanism is held ON.

Q34. What is a nontrip-free circuit breaker? A34. A circuit breaker that can be overridden if the operating mechanism is held ON.

Q35. Where should you use a trip-free circuit breaker?

A35. In current sensitive or nonemergency systems.

Q36. Where should you use a nontrip-free circuit breaker?

A36. In emergency or essential circuits.

Q37. What are the three time delay ratings for circuit breakers?

A37. Instantaneous, short time delay, and long time delay.

Q38. What is selective tripping and why is it used? A38. It is the use of time delay ratings to cause the circuit breaker closest to the faulty circuit to trip. This isolates the faulty circuit without affecting other circuits. Q39. If the power distribution system shown in figure 2-22 uses selective tripping, what is the time delay rating for each of the circuit breakers shown?

A39. CB1-long time delay; CB2, CB3-short time delay; CB4 through CB10-instantaneous.

NEETS Q&A

Q40. What factors are used to select a circuit breaker? A40. The power requirements of the circuit and the physical space available.

Q41. What type of circuit breaker is used on a multimeter? A41. A push button or push-pull circuit breaker (small size, low power). Q42. What steps are to be taken before beginning work on a circuit breaker? A42. Check the applicable technical manual, obtain the approval of the electrical or engineering officer (for shipboard circuit breakers), remove power from the circuit breaker, and tag the switch that supplies power to the circuit breaker. Q43. What items are you to check when working on a circuit breaker? A43. Check the operating mechanism for smooth operation, check the contacts for pitting, check the terminals for tightness and corrosion, check the mounting hardware for tightness and wear, check all components for wear, and check the entire circuit breaker for cleanliness.

COMMON TEST EQUIPMENT

Q-1. What is one of the greatest advantages of a VOM?

A-1. No external power source is required. Q-2. Before you connect a VOM in a circuit for an ohmmeter reading, in what condition must the circuit be?

A-2. De-energized. Q-3. When taking resistance readings with a VOM, you will obtain the most accurate readings at or near what part of the scale?

A-3. Midscale. Q-4. Besides setting up the meter for expected voltage ranges, what must be strictly observed when taking dc voltage readings?

A-4. Polarity. Q-5. Power for the electronic digital multimeter is normally supplied by what internal power source?

A-5. Rechargeable batteries. Q-6. How is an overload condition indicated by the electronic digital multimeter?

A-6. Simultaneous flashing of display readouts. Q-7. In an electronic digital multimeter, the digital information is displayed by what type of numerical readouts?

A-7. Light-emitting diodes.

Q-8. What is the general function of the differential voltmeter? A-8. To compare an unknown voltage with a known reference voltage and indicate the difference in their values.

SPECIAL-APPLICATION TEST EQUIPMENT

Q-1. To measure incident power, you must rotate the coupler-detector of the wattmeter so that the arrow indicating power flow points toward which end of the transmission line?

A-1. Load. Q-2. What condition produces the 10-kHz error signal generated by the metering bridge in the HP- 431C power meter?

A-2. An unbalance in the metering bridge. Q-3. In signal generators, what device is used to regulate the voltage of the output signal?

A-3. Attenuator. Q-4. Name the three main sections of a typical rf signal generator.

A-4. Oscillator circuit, modulator, and output control circuit.

Q-5. What is the function of the modulating circuit? A-5. To produce an af (or video) signal that can be superimposed on the rf signal produced by the oscillator. Q-6. What frequencies are provided through the back-panel BNC?

A-6. 1 MHz and 10 MHz. Q-7. The LED lamps of a typical logic probe are normally in what state?

A-7. DIM. Q-8. On the CRT display, what information is displayed in Quadrant 4?

A-8. Positive voltage (+V) and negative current ( −I). Q-9. When aligning the trace with a short applied to channel A, which control should be adjusted to bring the trace parallel to the vertical axis?

A-9. TRACE ROTATE control. Q-10. What minimum/maximum voltage level can be attained in the pulse generator section by adjusting the LEVEL control?

A-10. 0 to 5 volts. Q-11. Medium 1 range is designed to check what resistance values?

A-11. 50 ohms to 10K ohms.

COMPONENT TESTING

Q-1. Why are most ships limited in their ability to stock replacement modules for repair of electronic equipment?

A-1. Lack of adequate storage space.

Q-2. What is the most common cause of electron tube failure?

A-2. Open filaments.

Q-3. What is the most accurate method of determining the condition of an electron tube?

A-3. Testing the tube in its circuit.

Q-4. Normally, how are high-power rf tubes tested?

A-4. In their circuit.

Q-5. What should you do if a klystron becomes gassy? A-5. Restore it to serviceable condition by operating it temporarily at reduced beam voltage.

Q-6. When used as an amplifier, what is the best indication that a twt is operating properly?

A-6. Correct gain figure.

Q-7. What is the major advantage of a transistor over a tube?

A-7. Rugged design.

Q-8. Name two major disadvantages of transistors.

A-8. Sensitive to heat and minor overloads. Q-9. When you are using an ohmmeter to test a transistor, what range settings should be avoided? A-9. Any range setting that produces a current flow through the transistor that exceeds 1 milliamp (usually R x 1 range). Q-10. At approximately what minimum voltage potential should you be able to feel an electrostatic discharge?

A-10. 3,500 to 4,000 volts. Q-11. A MOSFET can be damaged by an electrostatic discharge at approximately what minimum potential?

A-11. 35 volts.

Q-12. Why should you avoid using ac-powered test equipment when wearing a wrist strap?

A-12. For your own safety.

Q-13. Prior to substituting a diode, what measurements should you take to determine its condition?

A-13. Voltages and resistances. Q-14. As a rule of thumb, what is an acceptable ratio of back-to-forward resistance for a diode?

A-14. Greater than 10 to 1. Q-15. When testing an SCR with an ohmmeter, the SCR will conduct if what two elements are shorted together?

A-15. Gate and anode. Q-16. When a Triac is properly gated, what is/are the direction(s) of current flow between anodes 1 and 2?

A-16. Current is allowed to flow in either direction.

Q-17. Why is it not advisable to use a solder sucker when working on MOSFETs? A-17. Solder suckers create an electrostatic charge capable of damaging a MOSFET.

Q-18. Name two advantages in using ICs.

A-18. Low power consumption, compact size, and lower cost.

Q-19. Why should you consider an IC as a black box? A-19. ICs cannot be repaired. All you need to test is output versus input.

Q-20. What are the two logic states of an IC?

A-20. A "1" or "0."

Q-21. A lighted LED on a logic clip represents what logic level?

A-21. A "1" state.

Q-22. What does a lighted LED indicate on a logic comparator? A-22. A difference in logic states between the reference IC and the IC under test.

Q-23. What is the purpose of a logic probe? A-23. They provide you with a visual indication of the logic state at any point you choose in the circuit. Q-24. Emergency eyewash facilities must be located within what minimum number of feet of an eyehazard area?

A-24. 10 feet. Q-25. What is the advantage of using a battery test set versus a voltmeter to test batteries?

A-25. A battery test set will test batteries under load conditions. Q-26. At what voltage is a NICAD battery considered to be fully discharged?

NEETS Q&A

A-26. At 1.1 volts. Q-27. What is the most common method of testing a fixed rf attenuator?

A-27. Rf substitution method.

Q-28. What is the most common method of testing resistive terminations?

A-28. Reading their resistances with a standard ohmmeter.

Q-29. What is the main disadvantage of using fiber-optic cables?

A-29. High attenuation. Q-30. What two features make the Huntron Tracker 2000 a widely used troubleshooting tool? A-30. It eliminates the need for multiple pieces of test equipment and it is lightweight and portable.

Q-31. What is the most preferred method of troubleshooting?

A-31. Testing components by comparison. Q-32. Why is it recommended to use more than one range while troubleshooting a device? A-32. Some defective devices may appear to be good in certain ranges.

Q-33. When you are testing individual components in a circuit, what may cause a defective component to appear good?

A-33. A parallel resistor or diode of similar value.

CONCEPTS OF ALTERNATING CURRENT

Q1. Define direct current.

A1. An electrical current which flows in one direction only.

Q2. Define alternating current. A2. An electrical current which is constantly varying in amplitude, and which changes direction at regular intervals. Q3. What is a disadvantage of a direct-current system with respect to supply voltage? A3. The dc voltage must be generated at the level required by the load. Q4. What disadvantage of a direct current is due to the resistance of the transmission wires?

A4. The I2R power loss is excessive.

Q5. What kind of electrical current is used in most modern power distribution systems?

A5. Alternating current (ac). Q6. When placed in the vicinity of a current-carrying conductor, the needle of a compass becomes aligned at what angle to the conductor?

A6. The needle aligns itself at right angles to the conductor. Q7. What is the direction of the magnetic field around a vertical conductor when (a) the current flows upward and (b) the current flows downward?

A7. (a) Clockwise (b) counterclockwise. Q8. The "left-hand rule" for a conductor is used for what purpose A8. It is used to determine the relation between the direction of the magnetic lines of force around a conductor and the direction of current through the conductor.

Q9. In what direction will the compass needle point when the compass is placed in the magnetic field surrounding a wire? A9. The north pole of the compass will point in the direction of the magnetic lines of force. Q10. When two adjacent parallel wires carry current in the same direction, the magnetic field about one wire has what effect on the magnetic field about the other conductor?

A10. It combines with the other field. Q11.When two adjacent parallel conductors carry current in opposite directions, the magnetic field about one conductor has what effect on the magnetic field about the other conductor?

A11. It deforms the other field. Q12. What is the shape of the magnetic field that exists around (a) a straight conductor and (b) a coil? A12. (a) The field consists of concentric circles in a plane perpendicular to the wire (b) the field of each turn of wire links with the fields of adjacent turns producing a two-pole field similar in shape to that of a simple bar magnet. Q13. What happens to the two-pole field of a coil when the current through the coil is reversed?

A13. The polarity of the two-pole field reverses. Q14. What rule is used to determine the polarity of a coil when the direction of the electron current flow in the coil is known?

A14. Use the left-hand rule for coils.

Q15. State the rule whose purpose is described in Q14. A15. Grasp the coil in your left hand, with your fingers "wrapped around" in the direction of electron flow. The thumb will point toward the north pole.

Q16. When a conductor is rotated in a magnetic field, at what points in the cycle is emf (a) at maximum amplitude and (b) at minimum amplitude? A16. (a) When the conductors are cutting directly across the magnetic lines of force (at the 90º and 270º points). (b) When the conductors are moving parallel to the magnetic lines of force (at the 0° , 180° , and 360° points). Q17. One cycle is equal to how many degrees of rotation of a conductor in a magnetic field?

A17. 360° Q18. State the left-hand rule used to determine the direction of current in a generator. A18. Extend your left hand so that your thumb points in the direction of conductor movement, and your forefinger points in the direction of the magnetic flux (north to south). Now point your middle finger 90° from the forefinger and it will point in the direction of electron current flow in the conductor.

Q19. How is an ac voltage produced by an ac generator? A19. Continuous rotation of the conductor through magnetic fines of force produces a series of cycles of alternating voltage or, in other words, an alternating voltage or a sine wave of voltage.

Q20. Define Frequency. A20. Frequency is the number of complete cycles of alternating voltage or current completed each second. Q21. What term is used to indicate the time of one complete cycle of a waveform?

A21. Period.

Q22. What is a positive alternation? A22. A positive alternation is the positive variation in the voltage or current of a sine curve. Q23. What do the period and the wavelength of a sine wave measure, respectively? A23. The period measures time and the wavelength measures distance.

Q24. What is meant by peak and peak-to-peak values of ac? A24. The peak value is the maximum value of one alternation; the peak-to-peak value is twice the maximum or peak value. Q25. How many times is the maximum or peak value of emf or current reached during one cycle of ac?

A25. Twice.

Q26. If any point on a sine wave is selected at random and the value of the current or voltage is measured at that one particular moment, what value is being measured?

A26. The instantaneous value (Einst or Iinst) Q27. What value of current or voltage is computed by averaging all of the instantaneous values during the negative alternation of a sine wave?

A27. Average value (Eavg or Iavg) Q28. What is the average value of all of the instantaneous currents or voltages occurring during one complete cycle of a sine wave?

A28. Zero Q29. What mathematical formulas are used to find the average value of current and average value of voltage of a sine wave? A29. Iavg = 0.636 x Imax

Eavg = 0.636 x Emax

Q30. If Emax is 115 volts, what is Eavg? A30. Eavg = 0.636 x 115 volts Eavg = 73.14 volts

Q31. If Iavg is 1.272 ampere, what is Imax?

A31. If Iavg = Imax x 0.636, then Imax = 0.636

Iavg= ampere

0.636

1.272 = 2

amperes Q32. What is the most convenient basis for comparing alternating and direct voltages and currents? A32. The power (heat) produced in a resistance by a dc voltage is compared to that produced in the same resistance by an ac voltage of the same peak amplitude.

Q33. What value of ac is used as a comparison to dc?

A33. The effective value. Q34. What is the formula for finding the effective value of an alternating current?

A34. Ieff = 0.707 x Imax

Q35. If the peak value of a sine wave is 1,000 volts, what is the effective (Eeff) value?

A35. Eeff = 0.707 x 1,000 volts = 707 volts

Q36. If Ieff = 4.25 ampere, what is Imax? A36. Imax = 1.414 x 4.25 amperes = 6 amperes (Remember: Unless specified otherwise, the voltage or current value is always considered

NEETS Q&A

to be the effective value.)

Q37. When are the voltage wave and the current wave in a circuit considered to be in phase? A37. When the two waves go through their maximum and minimum points at the same time and in the same direction. Q38. When are two voltage waves considered to be out of phase? A38. When the waves do not go through their maximum and minimum points at the same time, a PHASE DIFFERENCE exists, and the two waves are said to be out of phase. (Two waves are also considered to be out of phase if they differ in phase by 180° and their instantaneous voltages are always of opposite polarity, even though both waves go through their maximum and minimum points at the same time). Q39. What is the phase relationship between two voltage waves that differ in phase by 360° ?

A39. They are in phase with each other. Q40. How do you determine the phase difference between two sine waves that are plotted on the same graph? A40. Locate the points on the time axis where the two waves cross traveling in the same direction. The number of degrees between these two points is the phase difference.

Q41. A series circuit consists of three resistors (R1 = 10 Ω, R2 = 20 Ω, R3 = 15 Ω) and an alternating voltage source of 100 volts. What is the effective value of current in the circuit?

A41. Ieff = 45

100= 2.22 amperes

Q42. If the alternating source in Q41 is changed to 200 volts peak-to-peak, what is Iavg?

A42. Iavg = 0.636 × Imax = 1.41 amperes.

Q43. If Eeff is 130 volts and Ieff is 3 amperes, what is the total resistance (RT) in the circuit?

A43. 43.3 ohms.

DATA REPRESENTATION AND COMMUNICATIONS

Q-1. What is a general term used to describe raw facts?

A-1. Data.

Q-2. How is data represented?

A-2. By symbols.

Q-3. What were the first computers designed to manipulate in order to solve arithmetic problems?

A-3. Numbers.

Q-4. By what two means can the data contained on a source document be converted into a machinereadable form for processing?

A-4. By either direct or indirect means.

Q-5. What are some of the types of input media on which data may be indirectly entered?

A-5. Punched cards, paper tape, magnetic tape, or magnetic disk.

Q-6. What does the acronym EBCDIC stand for?

A-6. Extended Binary Coded Decimal Interchange Code.

Q-7. By using an 8-bit code, how many characters or bit combinations can be represented?

A-7. 256.

Q-8. What is the base of a hexadecimal number system?

A-8. 16.

Q-9. What term is used for the representation of two numeric characters stored in eight bits?

A-9. Packing or packed data.

Q-10. What does the acronym ASCII mean?

A-10. American Standard Code for Information Interchange.

Q-11. What was the purpose of several computer manufacturers cooperating to develop ASCII code for processing and transmitting data? A-11. To standardize a binary code to give the computer user the capability of using several machines to process data regardless of the manufacturer.

Q-12. Are there any differences in the concepts and advantages of ASCII and EBCDIC?

A-12. No, they are identical.

Q-13. How is the parity bit in each storage location used?

A-13. To detect errors in the circuitry.

Q-14. A computer or device that uses 8-bit ASCII or EBCDIC will use how many bits to store each character?

A-14. Nine.

Q-15. What area in the computer's primary storage area holds the processing instructions (the program)?

A-15. Program storage area.

Q-16. How are the boundaries determined for the separate areas of the computer's primary storage area?

A-16. By the individual programs being used.

Q-17. What is a bit?

A-17. A single binary digit.

Q-18. How many bits make up a byte?

A-18. Eight. Q-19. Primary storage capacities are usually specified in what unit of measure?

A-19. Number of bytes.

Q-20. How are core planes formed?

A-20. Magnetic cores are strung together on a screen of wire.

Q-21. Where are core planes used?

A-21. In primary storage. Q-22. Who designs and builds the storage capacity of an address into a computer?

A-22. The manufacturer. Q-23. What is another name for computers designed to be character-oriented or character-addressable?

A-23. Variable-word-length or byte-addressable. Q-24. Which computer has the faster calculating speeds, the variable-word-length or the fixed-word-length?

A-24. Fixed-word-length. Q-25. What is the normal organization of data recorded on magnetic storage media?

A-25. By bits, characters (bytes), fields, records, and files.

Q-26. What is a file?

A-26. A collection of related records. Q-27. Punched cards, paper tape, and magnetic tape use what storage access method?

A-27. Sequential-access.

Q-28. What kind of storage allows you to access the 125th record without having to read the 124 records in front of it?

A-28. Direct-access storage.

Q-29. Random-access storage media refers to what types of storage?

A-29. Magnetic core, semiconductor, thin film, and bubble. Q-30. Any system composed of one or more computers and terminals can be defined as what?

A-30. A network. Q-31. A network system allows dissimilar machines to do what within one universal system?

A-31. Exchange information.

Q-32. What does the make-up of a local area network consist of?

A-32. A communications facility and interface units. Q-33. How many designs of local area networks are there that can be used?

A-33. Two. Q-34. What are the different designs of local area networks called?

A-34. Broadband and baseband.

Q-35. What is a baseband communication channel like?

A-35. A party line.

Q-36. What do wide area networks provide for?

A-36. Global connections.

Q-37. Where does the word modem come from?

A-37. It is an acronym for modulator/demodulator.

Q-38. What are interface elements?

A-38. Those devices that serve to interconnect.

Q-39. How does a modem know when to expect data?

A-39. It is given a signal warning that data is about to be transmitted. Q-40. Whenever data is transferred between devices, it involves the exchange of prearranged signals; what is this process called?

A-40. Handshaking.

DEMODULATION

Q-1. What is demodulation? A-1. Re-creating original modulating frequencies (intelligence) from radio frequencies.

Q-2. What is a demodulator?

A-2. Circuit in which intelligence restoration is achieved.

Q-3. What is the simplest form of cw detector?

NEETS Q&A

A-3. A circuit that can detect the presence or absence of rf energy. Q-4. What are the essential components of a cw receiver system? A-4. An antenna, tank circuit for tuning, rectifier for detection, filter to give constant output, and an indicator device. Q-5. What principle is used to help distinguish between two cw signals that are close in frequency?

A-5. Heterodyning.

Q-6. How does heterodyning distinguish between cw signals?

A-6. By giving a different beat frequency for each signal. Q-7. What simple, one-transistor detector circuit uses the heterodyne principle?

A-7. Regenerative detector. Q-8. What three functions does the transistor in a regenerative detector serve?

A-8. Oscillator, mixer, and detector.

Q-9. What are the three requirements for an AM demodulator? A-9. (1) Sensitive to the type of modulation applied, (2) nonlinear, and (3) provide filtering. Q-10. What does the simplest diode detector use to reproduce the modulating frequency?

A-10. The modulation envelope. Q-11. What is the function of the diode in a series-diode detector?

A-11. Rectifies the rf pulses in the received signal.

Q-12. In figure 3-5, what is the function of C2? A-12. To filter the rf pulses and develop the modulating wave (intelligence) from the modulation envelope. Q-13. How does the current-diode detector differ from the voltage-diode detector?

A-13. The current-diode detector is in parallel with the input and load. Q-14. Under what circuit conditions would the shunt detector be used? A-14. When the input voltage variations are too small to give a usable output from a series detector. Q-15. Which junction of the transistor in the common-emitter detector detects the modulation envelope?

A-15. Emitter-base junction. Q-16. Which component in figure 3-7 develops the af signal at the input?

A-16. R1. Q-17. How is the output signal developed in the common-emitter detector?

A-17. By the collector current flow through R4. Q-18. Which junction acts as the detector in a common-base detector?

A-18. Emitter-base junction. Q-19. To what circuit arrangement is a common-base detector equivalent?

A-19. A diode detector followed by a stage of audio amplification. Q-20. In figure 3-8, which components act as the filter network in the diode detector?

A-20. C1 and R1.

Q-21. What is the simplest form of fm detector?

A-21. Slope detector.

Q-22. What is the function of an fm detector? A-22. Converting frequency variations of received fm signals to amplitude variations. Q-23. What type of tank circuit is used in the Foster-Seeley discriminator?

A-23. A double-tuned tank circuit. Q-24. What is the purpose of CR1 and CR2 in the Foster-Seeley discriminator?

A-24. Rectify the rf voltage from the discriminator. Q-25. What type of impedance does the tank circuit have above resonance?

A-25. Inductive.

Q-26. What is the primary advantage of a ratio detector?

A-26. Suppresses amplitude noise without limiter stages.

Q-27. What is the purpose of C5 in figure 3-12? A-27. It helps to maintain a constant circuit voltage to prevent noise fluctuations from interfering with the output. Q-28. What circuit functions does the tube in a gated-beam detector serve?

A-28. Limits, detects, and amplifies. Q-29. What condition must exist on both the limiter and quadrature grids for current to flow in a gated-beam detector?

A-29. Both grids must be positively biased.

Q-30. Name two advantages of the gated-beam detector.

A-30. Extreme simplicity, few components, and ease of adjustment. Q-31. Where is the intelligence contained in a phase-modulated signal?

A-31. In the amount and rate of phase shift of the carrier wave. Q-32. Why can phase-modulated signals be detected by fm detectors? A-32. Because of the incidental frequency shift that is caused while phase-shifting a carrier wave that is similar to fm modulation. Q-33. How is a quadrature detector changed when used for phase demodulation? A-33. The quadrature grid signal is excited by a reference from the transmitter. Q-34. In its simplest form, what functions must a radar detector be capable of performing?

A-34. Detecting the presence of rf energy. Q-35. What characteristic of a pulse does a peak detector sample?

A-35. Pulse amplitude or pulse duration. Q-36. What is the time constant of the resistor and capacitor in a peak detector for pam?

A-36. At least 10 times the interpulse period. Q-37. How can a peak detector for pam be modified to detect pdm? A-37. By making the time constant for charging the capacitor at least 10 times the maximum received pulse width.

Q-38. How does a low-pass filter detect pdm? A-38. By averaging the value of the pulses over the period of the pulse-repetition rate.

Q-39. How is conversion used in pulse demodulation? A-39. Ppm, pfm, and pcm are converted to either pdm or pam for demodulation. Q-40. What is the discharge rate for the capacitor in a pcm converter?

A-40. It will discharge to one-half its value between pulses.

DIGITAL MAGNETIC TAPE RECORDING

Q-1. In digital magnetic tape recording, the series of recorded digital pulses can represent what three types of data? A1. a. Data used by digital computers. b. Pulsed squarewave signals. c. Digitized analog waveforms.

Q-2. What three formats are used for digital magnetic tape recording?

A2. (1) Serial, (2) parallel, and (3) serial-parallel. Q-3. What format of digital tape recording is normally used to store computer data?

A3. Parallel digital magnetic tape recording. Q-4. What format of digital tape recording takes a serial input stream of data pulses, breaks them up, and records them on more than one data track?

A4. Serial-parallel digital magnetic tape recording. Q-5. What format of digital tape recording is normally used to record instrumentation or telemetry data?

A5. Serial digital magnetic tape recording. Q-6. Which of the eight methods for encoding digital data onto magnetic tape is most widely used because it’s accurate, simple, and reliable?

A6. Non-return-to-zero (NRZ) encoding. Q-7. Which digital data tape encoding method presets the magnetic tape to all zeros and then records digital ones onto the tape?

A7. Return-to-bias (RB) encoding. Q-8. Which digital data encoding method records a digital one as a positive pulse and a digital (zero) as a negative pulse and returns the tape to neutral between pulses?

A8. Return-to-zero (RZ) encoding. Q-9. Which method of digital data encoding does NOT return the tape to neutral between pulses but, instead, saturates the tape positively or negatively as the incoming data changes between zero and one?

A9. Non-return-to-zero (NRZ) encoding.

Q-10. What are the four widely used variations of the NRZ encoding method? A10. a. Non-return-to-zero level (NRZ-L). b. Enhanced non-return-to-zero level (E-NRZ-L). c. Non-return-to-zero mark (NRZ-M). d. Non-return-to-zero space (NRZ-S).

Q-11. Which digital data encoding method helps overcome a tape recorder’s low-frequency response problems by recording two logic levels for each incoming data bit?

A11. Bi-phase level encoding. Q-12. Digital magnetic tape recorders used to store and retrieve digital data fall into what three categories?

NEETS Q&A

A12. a. Computer-compatible digital tape recorders. b. Telemetry digital tape recorders. c. Instrumentation digital tape recorders. Q-13. What category of digital tape recorder is used for recording pulsed square-wave signals with a bandwidth of 500 kHz to 2 MHz?

A13. Telemetry digital tape recorders. Q-14. What category of digital tape recorder is used to record special signals with a bandwidth of less than 500 kHz?

A14. Instrumentation digital tape recorders.

DIRECT CURRENT

Q1. In figure 3-2, what part of the circuit is the (a) load and (b) source? A1. (a) DS1, the flashlight bulb (b) BAT, the dry cell

Q2. What happens to the path for current when S1 is open as shown in figure 3-2(A)? A2. The path for current is incomplete; or, there is no path for current with S1 open. Q3. What is the name given to the "picture" of a circuit such as the one shown in figure 3-2? A3. A schematic diagram.

Q4. According to Ohm’s law, what happens to circuit current if the applied voltage (a) increases, (b) decreases? A4. (a) Current increases (b) Current decreases Q5. According to Ohm’s law, what happens to circuit current if circuit resistance (a) increases, (b) decreases? A5. (a) Current decreases (b) Current increases

Q6. What is the equation used to find circuit resistance if voltage and current values are known?

A6. I

ER =

Q7. Using the graph in figure 3-7, what is the approximate value of current when the voltage is 12.5 volts? A7. 1.25 amperes. Q8. Using the graph in figure 3-8, what is the approximate value of current when the resistance is 3 ohms? A8. 4 amperes.

Q9. What is the term applied to the rate at which a mechanical or electrical force causes motion? A9. Power.

Q10. How can the amount of current be changed in a circuit? A10. By changing the circuit resistance or the voltage of the power source.

Q11. What are the three formulas for electrical power?

A11. R2

I P ,R

2E P I,EP ×==×=

Q12. What is the current in a circuit with 5 ohms of resistance that uses 180 watts of power? A12. 6 amperes. Q13. What type of resistor should be used in the circuit described in question 12? A13. A wirewound resistor.

Q14. What is the power used in a circuit that has 10 amperes of current through a 10-ohm resistor? A14. 1 kilowatt. Q15. How much power is converted by a 1-horsepower motor in 12 hours? A15. 8,952 watt hours or 8.952 kWh.

Q16. What is the efficiency of the motor if it actually uses 9.5 kWh in 12 hours? A16. 942 (rounded to 3 places). Q17. A series circuit consisting of three resistors has a current of 3 amps. If R1 = 20 ohms, R2= 60 ohms, and R 3 = 80 ohms, what is the (a) total resistance and (b) source voltage of the circuit? A17. (a) 160 ohms. (b) 480 ohms Q18. What is the voltage dropped by each resistor of the circuit described in question 17? A18. E1 = 60 volts. E2 = 180 volts. E3 = 240 volts. Q19. If the current was increased to 4 amps, what would be the voltage drop across each resistor in the circuit described in question 17? A19. E1 = 80 volts. E2 = 240 volts. E3 = 320 volts.

Q20. What would have to be done to the circuit described in question 17 to increase the current to 4 amps? A20. The source voltage would have to be increased to 640 volts. Q21. A series circuit consists of two resistors in series. R1 = 25 ohms and R2 = 30 ohms. The circuit current is 6 amps. What is the (a) source voltage, (b) voltage dropped by each resistor, (c) total power, and (d) power used by each resistor? A21. (a) 330 volts. (b) E1 = 150 volts. E2 = 180 volts. (c) 1.98 kilowatts. (d) P1 = 900 watts. P2 = 1.08 kilowatts

Q22. When using Kirchhoff’s voltage law, how are voltage polarities assigned to the voltage drops across resistors? A22. The point at which current enters the resistor is assigned a negative polarity and the point at which current leaves the resistor is assigned a positive polarity.

Q23. Refer to figure 3-27, if R1 was changed to a 40-ohm resistor, what would be the value of circuit current (I T)? A23. 2 amperes. Q24. Refer to figure 3-27. What is the effective source voltage of the circuit using the 40-ohm resistor? A24. 120 volts.

Q25. A circuit has a source voltage of 100 volts and two 50-ohm resistors connected in series. If the reference point for this circuit is placed between the two resistors, what would be the voltage at the reference point? A25. 50 volts.

Q26. If the reference point in question 25 were connected to ground, what would be the voltage level of the reference point? A26. Zero volts.

Q27. What is an open circuit? A27. A circuit where there is no longer a complete path for current flow.

Q28. What is a short circuit? A28. An accidental path of low resistance which passes an abnormally high amount of current. Q29. Why will a meter indicate more voltage at the battery terminal when the battery is out of a circuit than when the battery is in a circuit? A29. The internal (source) resistance of the battery will drop some of the voltage. Q30. What condition gives maximum power transfer from the source to the load? A30. When the load resistance equals the source resistance.

Q31. What is the efficiency of power transfer in question 30? A31. 50 percent. Q32. A circuit has a source voltage of 25 volts. The source resistance is 1 ohm and the load resistance is 49 ohms. What is the efficiency of power transfer?

A32. 98%

= × 100%

watts 12.5

watts 12.25

Q33. What would the source voltage (ES) in figure 3-39 be if the current through R2 were 2 milliamps? A33. 60 volts. Q34. There is a relationship between total current and current through the individual components in a circuit. What is this relationship in a series circuit and a parallel circuit? A34. Total current in a series circuit flows through every circuit component but in a parallel circuit total current divides among the available paths. Q35. In applying Kirchhoff’s current law, what does the polarity of the current indicate? A35. Whether the current is entering the junction (+) or leaving the junction (-). Q36. Four equal resistors are connected in parallel, each resistor has an ohmic value of 100 ohms, what is the equivalent resistance? A36. 25 ohms Q37. Three resistors connected in parallel have values of 12 kΩ, 20kΩ, and 30kΩ. What is the equivalent resistance? A37. 6kΩ Q38. Two resistors connected in parallel have values of 10 kΩ and 30kΩ. What is eht equivalent resistance? A38. 7.5kΩ Q39. What term identifies a single resistor that represents total resistance of a complex circuit? A39. Equivalent resistor or Req. Q40. The total power in both series and parallel circuits is computed with the formula: PT = P1 + P2 + P3 +...Pn. Why can this formula be used for both series and parallel circuits? A40. In both cases all the power used in the circuit must come from the source. Q41. A circuit consists of three resistors connected in parallel across a voltage source.R1 = 400Ω, R2 = 30 Ω, R3 = 40Ω, and PR3 = 360 watts. Solve for RT, ES and IR2. (Hint: Draw and label the circuit first.) A41. RT = 12Ω Q42. Refer to figure 3-55(A). If the following resistors were replaced with the values indicated: R1 = 900Ω, R3 = 1kΩ, what is the total power in the circuit? What is ER2? A42. PT = 60 W, ER2 = 10 V. Q43. What is the total resistance of the circuit shown in figure 3-59? (Hint: Redraw the circuit to simplify and then use equivalent resistances to compute for RT.) A43. 4Ω

Q44. What is the total resistance of the circuit shown in figure 3-

NEETS Q&A

60?

A44. 25Ω Q45. What effect does the internal resistance have on the rest of the circuit shown in figure 3-60? A45. Because of the 2-volt drop across the internal resistance, only 48 volts is available for the rest of the circuit. Q46. What is the effect on total resistance and total current in a circuit if an open occurs in (a) a parallel branch, and (b) in a series portion? A46. (a) Total resistance increases, total current decreases (b) Total resistance becomes infinite, total current is equal to zero

Q47. What is the effect on total resistance and total current in a circuit if a short occurs in (a) a parallel branch, and (b) in a series portion? A47. (a) Total resistance decreases, total current increases (b) Total resistance decreases, total current increases Q48. If one branch of a parallel network is shorted, what portion of circuit current flows through the remaining branches? A48. None. Q49. What information must be known to determine the component values for a voltage divider? A49. The source voltage and load requirements (voltage and current). Q50. If a voltage divider is required for a load that will use 450 mA of current, what should be the value of bleeder current? A50. 45 mA rule-of-thumb. Q51. If the load in question 50 requires a voltage of +90 V, what should be the value of the bleeder resistor? A51. 2 kΩ Q52. If the source voltage for the voltage divider in question 50 supplies 150 volts, what is the total current through the voltage divider? A52. 495 mA.

Q53. In figure 3-67, why is the value of R1 calculated first? A53. R1 is the bleeder resistor. Bleeder current must be known before any of the remaining divider resistor ohmic values can be computed. Q54. In figure 3-67, how is (a) the current through R2 and (b) the voltage drop across R2 computed? A54. (a) By adding the bleeder current (IR1) and the current through load 1(b) By subtracting the voltage of load 1 from the voltage of load 2.

Q55. In figure 3-67, what is the power dissipated in R1? A55. 1.35 watts. Q56. In figure 3-67, what is the purpose of the series-parallel network R 3, R 4, and R5? A56. The series-parallel network drops the remaining source voltage and is used to take the place of a single resistor (75 ohms) when the required ohmic value is not available in a single resistor. Q57. In figure 3-67, what should be the minimum wattage ratings of R 3 and R 5 ? A57. R3 = 2 watts; R5 = 6 watts. Q58. If the load requirement consists of both positive and negative voltages, what technique is used in the voltage divider to supply the loads from a single voltage source? A58. The ground (reference point) is placed in the proper point in the voltage divider so that positive and negative voltages are supplied. Q59. Is it considered safe for a person to touch any energized low-voltage conductor with the bare hand? A59. NEVER! All energized electric circuits should be considered potentially dangerous. Q60. What should you do if you become aware of a possible malfunction in a piece of electrical equipment? A60. You should immediately report this condition to a qualified technician.

Q61. Who should perform CPR? A61. Only trained, qualified personnel.

DIRECT CURRENT GENERATORS

Q1. Generators convert mechanical motion to electrical energy using what principle? A1. Magnetic induction. Q2. What rule should you use to determine the direction of induced emf in a coil? A2. The left-hand rule for generators.

Q3. What is the purpose of the slip rings? A3. To conduct the currents induced in the armature to an external load. Q4. Why is no emf induced in a rotating coil when it passes through the neutral plane? A4. No flux lines are cut. Q5. What component causes a generator to produce dc voltage rather than ac voltage at its output terminals? A5. A commutator

Q6. At what point should brush contact change from one

commutator segment to the next?

A6. The point at which the voltage is zero across the two segments. Q7. An elementary, single coil, dc generator will have an output voltage with how many pulsations per revolution? A7. Two. Q8. How many commutator segments are required in a two-coil generator? A8. Four

Q9. How can field strength be varied in a practical dc generator? A9. By varying the input voltage to the field coils. Q10. What causes sparking between the brushes and the commutator? A10. Improper commutation.

Q11. What is armature reaction? A11. Distortion of the main field due to the effects of armature current.

Q12. What is the purpose of interpoles? A12. To counter act armature reaction.

Q13. What is the effect of motor reaction in a dc generator? A13. A force which causes opposition to applied turning force.

Q14. What causes copper losses? A14. Resistance in the armature coils, which increases with temperature.

Q15. How can eddy current be reduced? A15. By laminating the core material. Q16. Why are drum-type armatures preferred over the Gramme-ring armature in modern dc generators? A16. Drum-type armatures are more efficient, because flux lines are cut by both sides of each coil. Q17. Lap windings are used in generators designed for what type of application? A17. Higher load currents are possible.

Q18. What are the three classifications of dc generators? A18. Series-wound, shunt-wound, and compound-wound.

Q19. What is the main disadvantage of series generators? A19. Output voltage varies as the load varies. Q20. What term applies to the voltage variation from no-load to full-load conditions and is expressed as a percentage? A20. Voltage regulation. Q21. What term applies to the use of two or more generators to supply a common load? A21. Parallel operation. Q22. What is the purpose of a dc generator that has been modified to function as an amplidyne? A22. It can serve as a power amplifier. Q23. What is the formula used to determine the gain of an amplifying device? A23. Gain = output ÷ input.

Q24. What are the two inputs to an amplidyne? A24. The mechanical force applied to turn the amplidyne, and the electrical input signal.

DIRECT CURRENT MOTORS

Q1. What factors determine the direction of rotation in a dc motor? A1. Direction of armature current, and direction of magnetic flux in field. Q2. The right-hand rule for motors is used to find the relationship between what motor characteristics? A2. Direction of conductor movement (rotation), direction of flux, and the direction of current flow. Q3. What are the differences between the components of a dc generator and a dc motor? A3. There are no differences.

Q4. What causes counter emf in a dc motor? A4. Generator action.

Q5. What motor characteristic is affected by counter emf? A5. Speed.

Q6. What is the load on a dc motor? A6. The device to be driven by the motor.

Q7. What is the main disadvantage of a series motor? A7. It must have a load connected to avoid damage from excess speed.

Q8. What is the main advantage of a series motor? A8. High torque (turning force) at low speed. Q9. What advantage does a shunt motor have over a series motor? A9. It maintains a constant speed under varying loads.

Q10. Why is the Gramme-ring armature not more widely used? A10. Only outside of coils cut flux (inefficient). Q11. How is the disadvantage of the Gramme-ring armature overcome in the drum-wound armature?

NEETS Q&A

A11. By winding the armature in a way that places the entire coil where it is exposed to maximum flux. Q12. In a dc motor that must be able to rotate in both directions, how is the direction changed? A12. By reversing either field or armature connections. Q13. What is the effect on motor speed if the field current is increased? A13. Motor will slow down. Q14. Armature reaction in a dc motor causes a shift of the neutral plane in which direction? A14. Opposite the rotation.

Q15. What current flows in the interpole windings? A15. Armature current.

Q16. What is the purpose of starting resistors? A16. To limit armature current until counter emf builds up.

ELECTRICAL CONDUCTORS

Q1. State the reason for the establishment of a "unit size" for conductors. A1. To allow comparisons between conductors of different sizes and resistance. Q2. Calculate the diameter in MILS of a conductor that has a diameter of 0.375 inch.

A2. 375 mils (move the decimal three places to the right).

Q3. Define a mil-foot. A3. A circular conductor with a diameter of 1 mil and a length of 1 foot.

Q4. Define a square mil as it relates to a square conductor. A4. The cross-sectional area of a square conductor with a side of 1 mil.

Q5. Define a circular mil. A5. The cross-sectional area of a circular conductor with a diameter of 1 mil. Q6. What is the circular mil area of a 19-strand conductor if each strand is 0.004 inch? A6. Circular mil area (CMA) = D2 (in mils) × number of strands0.0004 inch = 4 mils (CMA) = 4

2 ×19 (strands)(CMA) = 16 × 19 = 304 mils.

Q7. Define specific resistance.

A7. The resistance of a unit volume of a substance. Q8. List the three factors used to calculate resistance of a particular conductor in ohms. A8. Length, cross-sectional area, and specific resistance of a unit volume of the substance from which the conductor is made. Q9. Using table 1-2, determine the resistance of 1,500 feet of AWG 20 wire at 25º C.

A9. 1,000 ft = 10.4 ohms1,500 ft = 1.5 × 0.4 = 15.6 ohms Q10. When using an American Standard Wire Gauge to determine the size of a wire, where should you place the wire in the gauge to get the correct measurement?

A10. In the parallel walled slot not the circular area. Q11. List the four factors you should use to select wire for a specified current rating. A11. Conductor size, the material it is made of the location of the wire in a circuit, and the type of insulation used. Q12. What are three types of nonmetallic insulating materials that can be used in a high-temperature environments?

A12. FEP, extruded polytetrafluoroethylene, and silicone rubber. Q13. State why it is important for you to consider the ambient (surrounding) temperature of a conductor when selecting wire size. A13. The heat surrounding the conductor is an important part of total conductor heating. Q14. State two advantages of using aluminum wire for carrying electricity over long distances.

A14. It is light and reduces corona. Q15. State four advantages of copper over aluminum as a conductor. A15. It has higher conductivity, it is more ductile, it has relatively high tensile strength, and it can be easily soldered.

Q16. Define the temperature coefficient of resistance. A16. The amount of increase in the resistance of a 1-ohm sample of the conductor per degree of temperature rise above 0º C Q17. What happens to the resistance of copper when it is heated?

A17. It increases. Q18. Compare the resistance of a conductor to that of an insulator. A18. Conductors have a very low resistance and insulators have a resistance that is so great that, for all practical purposes, they are nonconductors.

Q19. State two fundamental properties of insulating materials.

A19. Insulation resistance and dielectric strength.

Q20. Define insulation resistance.

A20. The resistance to current leakage through the insulation.

Q21. Define dielectric strength. A21. The ability of the insulation material to withstand potential difference.

Q22. How is the dielectric strength of an insulator determined?

A22. By raising the voltage on a test sample until it breaks down. Q23. What is the purpose of coating a copper conductor with tin when rubber insulation is used? A23. To prevent the rubber insulation from deteriorating due to chemical action. Q24. What safety precaution should you take when working with extruded polytetrafluoroethylene insulated wiring?

A24. Avoid breathing the vapors when the insulation is heated.

Q25. State the reasons that the Navy is getting away from the use of asbestos insulation.

A25. Breathing asbestos fibers can cause lung disease and/or cancer Q26. State what happens to the insulating characteristics of asbestos when it gets wet.

A26. It will become a conductor. Q27. What are the most common insulators used for extremely high voltages?

A27. Varnished cambric and oil-impregnated paper.

Q28. What is the common name for enamel-insulated wire?

A28. Magnet wire. Q29. If a cable is installed where it receives rough treatment, what should be added?

A29. Metallic coat. Q30. How many categories of nonmetallic protective coverings are there?

A30. Three. Q31. What is the most common type of nonmetallic material used to protect wires and cables?

A31. Fibrous Braid.

Q32. What are the most common types of fibrous tape? A32. Rubber-filled cloth tape and a combination of cotton cloth and rubber. Q33. What materials are commonly used as cushions between cable insulation and metallic armor?

A33. Jute and Asphalt coverings.

Q34. What are the two types of metallic protection?

A34. Sheath and armor

Q35. What are the three types of lead-sheathed cables?

A35. Alloy lead, pure lead, and reinforced lead. Q36. What are the three examples of metallic armor cable that were discussed?

A36. Wire braid, steel tape, and wire armor

FIBER OPTIC CONCEPTS

Q1. Quantum physics successfully explained the photoelectric effect in terms of fundamental particles of energy called quanta. What are the fundamental particles of energy (quanta) known as when referring to light energy?

A1. Photons. Q2. What type of wave motion is represented by the motion of water?

A2. Transverse-wave motion. Q3. When light waves encounter any substance, what four things can happen? A3. Light waves are either transmitted, refracted, reflected, or absorbed. Q4. A substance that transmits almost all of the light waves falling upon it is known as what type of substance?

A4. Transparent. Q5. A substance that is unable to transmit any light waves is known as what type of substance?

A5. Opaque.

Q6. What is the law of reflection? A6. The law of reflection states that the angle of incidence is equal to the angle of reflection. Q7. When a wave is reflected from a surface, energy is reflected. When is the reflection of energy the greatest?

A7. When the wave is nearly parallel to the reflecting surface.

Q8. When is the reflection energy the least?

A8. When the wave is perpendicular to the reflecting surface.

NEETS Q&A

Q9. Light waves obey what law?

A9. The law of reflection. Q10. A refracted wave occurs when a wave passes from one medium into another medium. What determines the angle of refraction? A10. Depends on the bending caused by the velocity difference of the wave traveling through different mediums. Q11. A light wave enters a sheet of glass at a perfect right angle to the surface. Is the majority of the wave reflected, refracted, transmitted, or absorbed?

A11. Transmitted. Q12. When light strikes a piece of white paper, the light is reflected in all directions. What do we call this scattering of light?

A12. Diffusion. Q13. Two methods describe how light propagates along an optical fiber. These methods define two theories of light propagation. What do we call these two theories?

A13. The ray theory and the mode theory. Q14. What is the basic optical-material property relevant to optical fiber light transmission?

A14. The index of refraction. Q15. The index of refraction measures the speed of light in an optical fiber. Will light travel faster in an optically dense material or in one that is less dense?

A15. Light will travel faster in an optical material that is less dense. Q16. Assume light is traveling through glass, what happens when this light strikes the glass-air boundary? A16. Part of the light ray is reflected back into the glass and part of the light ray is refracted (bent) as it enters the air. Q17. What condition causes a light ray to be totally reflected back into its medium of propagation? A17. Total internal reflection occurs when the angle of refraction approaches 90 degrees. This condition occurs when the angle of incidence increases to the point where no refraction is possible. Q18. What name is given to the angle where total internal reflection occurs?

A18. Critical angle of incidence.

Q19. List the three parts of an optical fiber.

A19. Core, cladding, and coating or buffer. Q20. Which fiber material, core or cladding, has a higher index of refraction?

A20. Core. Q21. Light transmission along an optical fiber is described by two theories. Which theory is used to approximate the light acceptance and guiding properties of an optical fiber?

A21. The ray theory. Q22. Meridional rays are classified as either bound or unbound rays. Bound rays propagate through the fiber according to what property?

A22. Total internal reflection. Q23. A light ray incident on the optical fiber core is propagated along the fiber. Is the angle of incidence of the light ray entering the fiber larger or smaller than the acceptance angle (ÿa)

A23. Smaller. Q24. What fiber property does numerical aperture (NA) measure?

A24. NA measures the light-gathering ability of an optical fiber. Q25. Skew rays and meridional rays define different acceptance angles. Which acceptance angle is larger, the skew ray angle or the meridional ray angle?

A25. Skew ray angle. Q26. The mode theory uses electromagnetic wave behavior to describe the propagation of the light along the fiber. What is a set of guided electromagnetic waves called?

A26. Modes of the fiber. Q27. A light wave can be represented as a plane wave. What three properties of light propagation describe a plane wave?

A27. Direction, amplitude, and wavelength of propagation. Q28. A wavefront undergoes a phase change as it travels along the fiber. If the wavefront transverses the fiber twice and is reflected twice and the total phase change is equal to 1/2 p, will the wavefront disappear? If yes, why? A28. Yes, the wavefront will disappear because the total amount of phase collected must be an integer multiple of 2 p. (If the propagating wavefronts are out of phase, they will disappear. The wavefronts that are in phase interfere with the wavefronts out of phase. This type of interference is called destructive interference.) Q29. Modes that are bound at one wavelength may not exist at longer wavelengths. What is the wavelength at which a mode ceases to be bound called?

A29. Cutoff wavelength.

Q30. What type of optical fiber operates below the cutoff

wavelength?

A30. Multimode fiber. Q31. Low-order and high-order modes propagate along an optical fiber. How are modes determined to be low-order or high-order modes? A31. The order of a mode is indicated by the number of field maxima within the core of the fiber. The order of a mode is also determined by the angle that the wavefront makes with the axis of the fiber. Q32. As the core and cladding modes travel along the fiber, mode coupling occurs. What is mode coupling?

A32. Mode coupling is the exchange of power between two modes. Q33. The fiber's normalized frequency (V) determines how many modes a fiber can support. As the value of V increases, will the number of modes supported by the fiber increase or decrease?

A33. Increase. Q34. The value of the normalized frequency parameter (V) relates the core size with mode propagation. When single mode fibers propagate only the fundamental mode, what is the value of V?

A34. V≤2.405. Q35. The number of modes propagated in a multimode fiber depends on core size and numerical aperture (NA). If the core size and the NA decrease, will the number of modes propagated increase or decrease?

A35. Decrease. Q36. Modal dispersion affects the bandwidth of multimode systems. It is essential to adjust what three fiber properties to maximize system bandwidth?

A36. Core diameter, NA, and index profile properties.

Q37. Attenuation is mainly a result of what three properties?

A37. Light absorption, scattering, and bending losses.

Q38. Define attenuation. A38. Attenuation is the loss of optical power as light travels along the fiber.

Q39. What are the main causes of absorption in optical fiber?

A39. Intrinsic and extrinsic material properties. Q40. Silica (pure glass) fibers are used because of their low intrinsic material absorption at the wavelengths of operation. This wavelength of operation is between two intrinsic absorption regions. What are these two regions called? What are the wavelengths of operation for these two regions? A40. Ultraviolet absorption region (below 400 nm) and infrared absorption region (above 2000 nm). Q41. Extrinsic (OH) absorption peaks define three regions or windows of preferred operation. List the three windows of operation. A41. The first, second, and third windows of operation are 850 nm, 1300 nm, and 1550 nm, respectively. Q42. What is the main loss mechanism between the ultraviolet and infrared absorption regions?

A42. Rayleigh scattering. Q43. Scattering losses are caused by the interaction of light with density fluctuations within a fiber. What are the two scattering mechanisms called when the size of the density fluctuations is (a) greater than and (b) less than one-tenth of the operating wavelength?

A43. (a) Mie scattering; (b) Rayleigh scattering. Q44. Microbend loss is caused by microscopic bends of the fiber axis. List three sources of microbend loss. A44. Uneven coating applications, improper cabling procedures, and external force.

Q45. How is fiber sensitivity to bending losses reduced? A45. Fiber sensitivity to bending losses can be reduced if the refractive index of the core is increased and/or if the overall diameter of the fiber increases. Q46. Name the two types of intramodal, or chromatic, dispersion.

A46. Material dispersion and waveguide dispersion. Q47. Which dispersion mechanism (material or waveguide) is a function of the size of the fiber's core relative to the wavelength of operation?

A47. Waveguide dispersion. Q48. Modes of a light pulse that enter the fiber at one time exit the fiber at different times. This condition causes the light pulse to spread. What is this condition called?

A48. Modal dispersion.

FIBER OPTIC LINKS

Q1. List four system topologies that can be constructed using point-to-point fiber optic links.

A1. Linear bus, ring, star, and tree topologies.

Q2. Which topology (linear bus, ring, star, or tree) consists of

NEETS Q&A

equipments attached to one another in a closed loop?

A2. Ring. Q3. Which topology (bus, ring, star, or tree) has a center hub interconnecting the equipments?

A3. Star.

Q4. Define modulation. A4. The process of varying one or more characteristics of an optical signal to encode and convey information.

Q5. What is a digital signal? A5. A discontinuous signal that changes from one state to another in discrete steps. Q6. In NRZ code, does the presence of a high-light level in the bit duration represent a binary 1 or a binary 0?

A6. Binary 1.

Q7. How can the loss of timing occur in NRZ line coding? A7. If long strings of 1s or 0s are present causing a lack of level transitions.

Q8. How is a binary 1 encoded in RZ line coding? A8. A half-period optical pulse present in the first half of the bit duration. Q9. In Manchester encoding, does a low-to-high light level transition occurring in the middle of the bit duration represent a binary 1 or a binary 0?

A9. Binary 0.

Q10. What is an analog signal? A10. A continuous signal that varies in a direct proportion to the instantaneous value of a physical Q11. What type of modulation do most analog fiber optic communications systems use?

A11. Intensity modulation. Q12. Why has the transmission of video using analog techniques been very popular, especially for shorter distances? A12. Because cost can be minimized and complex multiplexing and timing equipment is unnecessary. Q13. Why is it generally only necessary to refer to point-to-point data links when discussing the process of fiber optic system design? A13. Because fiber optic systems that incorporate complex architectures can be simplified into a collection of point-to-point data links before beginning the design process. Q14. List five system design parameters considered when system designers choose the system operational wavelength and link components. A14. Launch power, connection losses, bandwidth, cost, and reliability. Q15. What two analyses are performed to determine if a link design is viable?

A15. Power budget and risetime budget. Q16. Optical fibers or cables should never be bent at a radius of curvature smaller than a certain value. Identify this radius of curvature.

A16. Minimum bend radius. Q17. List five precautions to take when installing fiber optic systems on board naval ships. A17. a. Never bend an optical fiber or cable at a radius of curvature less than the minimum bend radius. b. Never pull fiber optic cables tight or fasten them over or through sharp corners or cutting edges. c. Always clean fiber optic connectors before mating. d. Do not kink or crush fiber optic cable during installation of the hardware. e. Allow only trained, authorized personnel to install or repair fiber optic systems.

FIBER OPTIC MEASUREMENT TECHNIQUES

Q1. List the fiber geometrical measurements performed in the laboratory. A1. Cladding diameter, core diameter, numerical aperture, and mode field diameter. Q2. End users measure the total attenuation of a fiber at the operating wavelength (l). Write the equation for total attenuation (A), between an arbitrary point X and point Y located on an optical fiber.

A2. Q3. Will an optical fiber's attenuation coefficient vary with changes in wavelength?

A3. Yes. Q4. What two properties of the launch condition may affect multimode fiber attenuation measurements?

A4. Launch spot size and angular distribution. Q5. Does underfilling a multimode optical fiber excite mainly high-order or low-order modes?

A5. Low-order modes.

Q6. Multimode optical fiber launch conditions are typically characterized as being overfilled or underfilled. Which of these optical launch conditions exists if the launch spot size and angular distribution are larger than that of the fiber core?

A6. Overfilled. Q7. A mode filter is a device that attenuates specific modes propagating in the core of an optical fiber. What mode propagating along single mode fibers do mode filters eliminate?

A7. Second-order mode.

Q8. What are the two most common types of mode filters?

A8. Free-form loop and mandrel wrap. Q9. The cutoff wavelength of matched-clad and depressed-clad single mode fibers varies according to the fiber's radius of curvature and length. The cutoff wavelength of which single mode fiber type is more sensitive to length?

A9. Depressed-clad. Q10. Will the cutoff wavelength of uncabled fibers (lcf) generally have a value higher or lower than the cutoff wavelength of cabled fibers (λcc)?

A10. Higher.

Q11. Describe the -3 decibel (dB) optical power frequency (f3dB). A11. The -3 decibel (dB) is the lowest frequency at which the magnitude of the fiber frequency response has decreased to one half its zero-frequency value. Q12. Delay differences between the source wavelengths occur as the optical signal propagates along the fiber. What is this called?

A12. Differential group delay t(l). Q13. What determines the range of wavelengths over which meaningful data is obtained for calculating the chromatic dispersion?

A13. The wavelength range of the optical source(s) used. Q14. Why do end users perform fiber geometry measurements in the laboratory? A14. To reduce system attenuation and coupling loss resulting from poor fiber fabrication.

Q15. Define cladding diameter.

A15. The cladding diameter is the average diameter of the cladding. Q16. Explain the difference between multimode and single mode core-cladding concentricity errors. A16. Multimode core-cladding concentricity error is the distance between the core and cladding centers expressed as a percentage of core diameter while the single mode core-cladding concentricity error is just the distance between the core and cladding centers. Q17. Near-field power distributions describe the emitted power per unit area in the near-field region. Describe the near-field region.

A17. The near-field region is the region close to the fiber-end face.

Q18. How is the core diameter defined? A18. The core diameter is defined as the diameter at which the near-field intensity is 2.5 percent of the maximum intensity. Q19. Far-field power distributions describe the emitted power per unit area as a function of angle θ in the far-field region. Describe the far-field region.

A19. The far-field region is the region far from the fiber-end face. Q20. Will fiber coupling loss generally increase or decrease if the mode field diameter of a single mode fiber is decreased?

A20. Increase. Q21. In multimode fibers, how do fiber joints increase fiber attenuation following the joint?

A21. By disturbing the fiber's mode power distribution (MPD).

Q22. List two effects that reflections can have on a fiber optic data link. A22. Reduce the stability of the system source and increase the signal noise present at the optical detector.

Q23. Reflectance is given as what ratio?

A23. The ratio of reflected optical power to incident optical power. Q24. Does return loss include power that is transmitted, absorbed, and/or scattered?

A24. No. Q25. Is it essential for end users to remeasure optical fiber geometrical properties after installation in the field?

A25. No. Q26. When is an OTDR recommended for conducting field measurements on installed optical fibers or links? A26. When installed optical fiber cables or links are 50 meters or more in length. Q27. An OTDR measures the fraction of light that is reflected back from the fiber or link under test. What causes light to be reflected back into the OTDR?

NEETS Q&A

A27. Rayleigh scattering and Fresnel reflection. Q28. List the types of fiber optic components considered part of a fiber optic cable plant. A28. Optical fiber cables, connectors, splices, mounting panels, jumper cables, and other passive components. Q29. What is a temporary or permanent local deviation of the OTDR signal in the upward or downward direction called?

A29. A point defect. Q30. Why is a dead-zone fiber placed between the test fiber and OTDR when conducting attenuation measurements?

A30. To reduce the effect of the initial reflection at the OTDR. Q31. The amount of backscattered optical power at each point depends on what two properties?

A31. Forward optical power and backscatter capture coefficient. Q32. How can test personnel eliminate the effects of backscatter variations? A32. By performing the OTDR attenuation measurements in each direction along the test fiber. Q33. If the length of the fiber point defect changes with pulse duration, is the OTDR signal deviation a point defect or a region of high fiber attenuation?

A33. A point defect. Q34. Give the type of fault (reflective or nonreflective) normally produced by: (a) fiber breaks, (b) fiber cracks, and (c) fiber microbends.

A34. (a) Reflective, (b) nonreflective, and (c) nonreflective.

Q35. Explain how a point defect may exhibit an apparent gain. A35. A point defect may exhibit apparent gain because the backscatter coefficient of the fiber present before the point defect is higher than that of the fiber present after. Q36. A point defect exhibiting an apparent gain in one direction will exhibit what, when measured in the opposite direction?

A36. An exaggerated loss. Q37. When is an optical power meter measurement recommended for conducting field measurements on installed optical fiber cables or cable plants? A37. When an installed optical fiber cable or cable plant is less than 50 meters in length. Q38. If an installed optical fiber cable does not have connectors or terminations on both ends, how should the cable be tested? A38. With an OTDR unless it is less than 50 meters in length. If it is less than 50 meters in length, continuity should be verified with a flashlight.

FUNDAMENTAL LOGIC CIRCUITS

Q1. What is defined as "the science of reasoning?"

A1. Logic. Q2. With regard to computer logic circuits, what is meant by "complement?"

A2. The opposite of the original statement.

Q3. What are the complements of the following terms?

a. Q

b. R

c. V

d. Z

A3.

a. Q’

b. R’

c. V’

d. Z’ Q4. If logic 1 = -5 vdc and logic 0 = -10 vdc, what logic polarity is being used?

A4. Positive. Q5. If logic 1 = +2 vdc and logic 0 = -2 vdc, what logic polarity is being used?

A5. Positive. Q6. If logic 1 = -5 vdc and logic 0 = 0 vdc, what logic polarity is being used?

A6. Negative. Q7. What is the Boolean expression for the output of an AND gate that has R and S as inputs?

A7. f = RS. Q8. What must be the logic state of R and S to produce the TRUE output?

A8. Both must be 1s (HIGH) at the same time. Q9. How many input combinations exist for a four-input AND gate?

A9. 16.

Q10. Write the Boolean expression for an OR gate having G, K,

and L as inputs.

A10. f = G+K+L. Q11. How many input combinations are possible using G, K, and L?

A11. Eight. Q12. How many of those combinations will produce a HIGH output?

A12. Seven.

Q13. What is the complement of XYZ?

A13. XYZ

Q14. The input to an inverter is X + (YZ). What is the output

A14. X + (YZ). Q15. In a properly functioning circuit, can both the input and output of an inverter be HIGH at the same time?

A15. No. Q16. A NAND gate has Z and X as inputs. What will be the output logic level if Z is HIGH and X is LOW?

A16. HIGH. Q17. What must be the state of the inputs to a NAND gate in order to produce a LOW output?

A17. All inputs must be HIGH. Q18. What is the output Boolean expression for a NAND gate with inputs A, B, and C?

A18. C B A Q19. A NAND gate has inputs labeled as A, B, and C. If A and B are HIGH, C must be at what logic level to produce a HIGH output?

A19. Low.

Q20. How does a NOR gate differ from an OR gate?

A20. It has an inverter on the output. Q21. What will be the output of a NOR gate when both inputs are HIGH?

A21. Low. Q22. What is the output Boolean expression for a NOR gate with R and T as inputs?

A22. (R +T)’ Q23. In what state must the inputs to a NOR gate be in order to produce a logic 1 output?

A23. All inputs must be low. Q24. What is the output Boolean expression for an AND gate with A and B as inputs when the B input is inverted?

A24. AB . Q25. What is the equivalent logic gate of a two-input NAND gate with both inputs inverted?

A25. OR gate. Q33. Boolean algebra is based on the assumption that most quantities have _______ conditions.

A33. Two. Q34. Boolean algebra is used primarily by _______ to simplify circuits.

A34. Design engineers.

FUNDAMENTAL SYSTEMS EQUIPMENT

Q1. What are the basic functions of a handset? A1. To convert energy electrical/acoustic to acoustic/electrical and to key/unkey a transmitter. Also it mutes a receiver when transmitting. Q2. What capability does a transmitter transfer switchboard provide?

A2. Transferring remote control functions and signals to transmitters. Q3. What function does a receiver transfer switchboard perform?

A3. Transfers receiver audio outputs to remote control stations. Q4. If the rf amplifier discussed has an 80 milliwatt input, what would be the maximum output?

A4. 800 watts.

Q5. What are the tuning modes for the coupler group discussed?

A5. Automatic, semiautomatic, and manual.

Q6. What is the purpose of an antenna coupler? A6. It matches the impedance of an antenna to that of a transmission line at any desired frequency.

Q7. Why is the coupler pressurized with nitrogen?

A7. To aid in heat transfer and prevent corona and arcing.

Q8. What are the transmitter operating modes?

A8. Lsb, usb, isb, AM, cw, fsk.

Q9. What type of tuning does the receiver use?

A9. Digital.

NEETS Q&A

Q10. What is the function of an antenna patch panel? A10. To connect an antenna/transmission line to a receiver/transmitter.

Q11. What are the functions of a multicoupler? A11. Patching and filtering and permits the multiple use of receivers and/or transmitters on a single antenna. Q12. What are the terms used to describe an open or closed telegraph circuit?

A12. Space and mark.

Q13. How many units are in a tty signal and what are they?

A13. Intelligence (5), start (1), stop (1). Q14. There are not enough combinations of the five-unit code to handle the alphabet, symbols and so forth. What is used to increase the number of available code combinations?

A14. Shift signals.

Q15. What are the two teletypewriter modes of operation?

A15. Synchronous and nonsynchronous.

Q16. Define baud.

A16. A unit of modulation rate.

Q17. Define bit.

A17. Binary digit. Q18. What are the two types of dc operations used to represent mark and space conditions?

A18. Neutral and polar.

Q19. What is the function of a keyer?

A19. Converts dc to corresponding mark and space modulation.

Q20. What is the function of a converter?

A20. Converts the audio signal to dc pulses.

Q21. Basically describe an afts system.

A21. Uses AM to change dc to audio.

Q22. Basically describe an rfcs system. A22. A keyer provides rf excitation, which can be shifted above or below the assigned frequency.

Q23. Most Navy tty sets operate at what speeds?

A23. 60, 75, or 100 wpm.

Q24. A receive tty set provides outputs in what formats?

A24. Page-size copy paper and perforated tape.

Q25. What does the color red indicate on a tty patch panel?

A25. It handles classified information.

Q26. What are the functions of cryptographic equipment?

A26. To code or decode messages.

Q27. What are the functions of a converter-comparator group? A27. The comparator compares the signal strengths from the receivers and the converter converts the frequency-shift rf signal into a tty set dc loop control signal.

Q28. What is the function of a tone terminal set?

A28. It converts dc to audio or vice versa.

Q29. What are the two types of multiplexing?

A29. Time-division and frequency-division.

Q30. What is the purpose of multiplexing? A30. It allows simultaneous transmission of multiple signals on a single transmission path. Q31. The transmission of still images over an electrical communications system is known as what?

A31. Facsimile.

Q32. The term TEMPEST refers to what?

A32. Compromising emanations. Q33. What are the three fundamental requirements of a military communications system?

A33. Reliability, security, and speed.

Q34. Which of the above requirements is most important?

A34. Reliability.

Q35. What is the purpose of QMCS? A35. To ensure continuous, optimum performance of communications systems.

Q36. What is emi?

A36. Electromagnetic interference.

Q37. What are the two emi transmission methods?

A37. Conduction and radiation. Q38. Electromagnetic radiation is hazardous to personnel in what two ways?

A38. Rf burns and biological, thermal, and neurological effects.

Q39. What is the most useful and widespread technique to

reduce rf burn hazards?

A39. Proper bonding and grounding.

GYROS

Q-1. Can any rapidly spinning object be considered a gyroscope?

A-1. Yes. Q-2. In the drawing in figure 3-1, which axis is the gyro spin axis?

A-2. X-axis. Q-3. What gyro property causes the gyro to remain in a fixed position?

A-3. Rigidity.

Q-4. What type(s) of force does a gyro resist?

A-4. Any force that attempts to tilt the spin axis. Q-5. In what direction will a gyro precess in response to an outside force?

A-5. Perpendicular (90º) to the force.

Q-6. A universally mounted gyro has how many gimbals?

A-6. Two.

Q-7. What factors determine the rigidity of a gyro?

A-7. Rotor speed, weight, shape. Q-8. Which gyro rotor in figure 3-6, view (A) view (B) view (C), will have the greatest rigidity if all are rotated at the same speed?

A-8. C. Q-9. What type of force acts ONLY through the center of gravity of a gyro, and does NOT cause precession?

A-9. Force of translation. Q-10. The amount of precession that results from a given force is determined by what quantity?

A-10. Rigidity. Q-11. What factor determines the direction a gyro will precess in response to a particular force?

A-11. Direction of spin. Q-12. When using the tight-hand rule to determine precession, which finger indicates the direction of the applied force?

A-12. Middle finger. Q-13. A universally mounted gyro has how many degrees of freedom?

A-13. Two. Q-14. If a free gyro is placed at the equator at 1200 in a vertical position; in what position should it be at 1800?

A-14. Horizontal.

Q-15. What are the three causes of mechanical drift in a gyro?

A-15. Unbalanced gyro, inertia of gimbals, bearing friction. Q-16. What is the purpose of an erection system used with a gyro? A-16. To achieve and maintain the proper operating position for the gyro (usually vertical or horizontal). Q-17. What is the purpose of rotating the gimbal assembly in a gyro using a mercury erection system?

A-17. Applies torque at the proper point for correct precession.

Q-18. What are rate gyros primarily used for?

A-18. Measuring angular rates. Q-19. How many degrees-of-freedom does a rate gyro usually have?

A-19. One. Q-20. What gyro characteristic provides the basis of the operation of a rate gyro?

A-20. Precession. Q-21. Operation of an accelerometer is based on what physical property?

A-21. Inertia.

Q-22. What type of systems primarily use accelerometers?

A-22. Navigation systems. Q-23. What special requirement is the pulse counting accelerometer designed for?

A-23. When digital data is required from an accelerometer.

RELATED DEVICES Q-1. What two characteristics of IC synchros cause them to differ from standard synchros?

A-1. Direction of rotation and amount of torque. Q-2. Compare the power sources of synchros and step-transmission systems.

A-2. Synchros use ac; step transmission uses dc.

NEETS Q&A

Q-3. A step transmitter is a modification of what electrical device?

A-3. Rotary switch.

Q-4. What type of mathematical problem is solved by resolvers?

A-4. Right-triangle, or trigonometric, problems.

HARDWARE

Q-1. What is the brain of a computer system?

A-1. The central processing unit.

Q-2. How many sections make up the central processing unit?

A-2. Three.

Q-3. What are the names of the sections that make up the cpu? A-3. Control section, internal storage section, and arithmetic-logic section.

Q-4. The control section can be compared to what?

A-4. A telephone exchange. Q-5. What are the four major types of instructions in the control section?

A-5. Transfer, arithmetic, logic, and control. Q-6. What capability allows the arithmetic/logic section to test various conditions encountered during processing and take action based on the result?

A-6. Logic. Q-7. In the arithmetic/logic section, data is returned to what section after processing?

A-7. Internal storage. Q-8. What is the process by which instructions and data are read into a computer?

A-8. Loading.

Q-9. Magnetic core storage is made up of what?

A-9. Tiny doughnut-shaped rings made of ferrite iron.

Q-10. A semiconductor memory consists of what? A-10. Hundreds of thousands of tiny electronic circuits etched on a silicon chip.

Q-11. What is another name for semiconductor memory chips?

A-11. Integrated circuits.

Q-12. In computer storage, what does volatile mean?

A-12. All data in memory is lost when the power source is removed. Q-13. What type of storage can retain its data even if there is a power failure or breakdown? A-13. Nonvolatile (magnetic core storage and bubble memory are examples).

Q-14. Bubble memory consists of what?

A-14. A very thin crystal made of semiconductor material. Q-15. How are the magnetic domains of a bubble memory switched? A-15. By passing a current through a control circuit imprinted on top of the crystal. Q-16. What do we mean when we say that reading from bubble memory is nondestructive?

A-16. The data is still present after being read. Q-17. In what type of memory are often used instructions and programs permanently stored inside the computer?

A-17. Read-only memory (ROM).

Q-18. Who provides the programs stored in ROM?

A-18. Only the manufacturer.

Q-19. Can programs in ROM be changed?

A-19. No.

Q-20. What is another name for random-access memory (RAM)?

A-20. Read/write memory.

Q-21. How is data read from or written into RAM? A-21. By giving the computer the address of the location where the data is stored or is to be stored. Q-22. In what two states can programmable read-only memory (PROM) be purchased?

A-22. Already programmed by the manufacturer or in a blank state.

Q-23. What is the main disadvantage of PROM? A-23. If a mistake is made and entered, it cannot be corrected or erased.

Q-24. What does EPROM stand for?

A-24. Erasable programmable read-only memory.

Q-25. How is EPROM erased?

A-25. With a burst of ultra-violet light.

Q-26. Why are disk storage devices popular?

A-26. Largely because of their direct access capabilities.

Q-27. How is data stored on all disks?

A-27. In a number of invisible concentric circles called tracks.

Q-28. What precedes each record on a disk?

A-28. A disk address.

Q-29. How is the storage capacity of a disk determined?

A-29. By the bits per inch of track and the tracks per inch of surface. Q-30. What two ways can data be physically organized on a disk pack?

A-30. By cylinder or sector. Q-31. The amount of data that can be stored on a linear inch of tape is known by what term?

A-31. Recording density. Q-32. The length of tape between BOT and EOT is referred to by what term? A-32. The usable recording (reading/writing) surface or usable storage area.

Q-33. How does a magnetic drum differ from a magnetic disk? A-33. The tracks in which the data is stored are assigned to channels that form circular bands around the drum. Q-34. Tracks on each channel of a magnetic drum are grouped into what?

A-34. Sectors.

Q-35. What is the purpose of any magnetic tape unit?

A-35. To write data on or read data from a magnetic tape. Q-36. What are the major differences between magnetic tape units? A-36. The speed at which the tape is moved past the read/write head and the density of the recorded information. Q-37. Why is direct accessing of data a big advantage over the sequential accessing of data? A-37. It gives us fast, immediate access to specific data without having to examine each and every record from the beginning.

Q-38. What is a floppy disk? A-38. A thin, flexible platter coated with magnetic material so characters can be recorded.

Q-39. What are the three most common sizes of floppy disks?

A-39. 8 inch, 5 1/4 inch, and 3 1/2 inch. Q-40. What output device expresses coded characters as hard copy (paper documents)?

A-40. Printers. Q-41. What four types of printers are commonly used with personal computers?

A-41. Daisy-wheel, dot-matrix, ink jet, and laser.

Q-42. What is the primary purpose of a keyboard?

A-42. To enter or input alphanumeric character codes. Q-43. Raster scan or tv scan video monitors are used extensively for what purpose?

A-43. The display of alphanumeric data and graphics.

Q-44. How many fields make up a frame?

A-44. Two.

Q-45. A field is approximately how many horizontal lines?

A-45. 525.

Q-46. What are picture elements often called?

A-46. Pixels or pels.

Q-47. Vertical resolution depends on what?

A-47. The number of horizontal scan lines used. Q-48. Flat panel displays are designed to reduce what problem of a crt display? A-48. Reduce the depth of the crt display caused by the length of the tube. Q-49. What does the liquid crystal display require for computer applications?

A-49. An external light source, called a backlight.

INDUCTANCE

Q1. What is the basic unit of inductance and the abbreviation for this unit?

A1. The henry, H. Q2. An emf is generated in a conductor when the conductor is cut by what type of field?

A2. Magnetic field.

Q3. Define inductance.

NEETS Q&A

A3. Inductance is the property of a coil (or circuit) which opposes any CHANGE in current.

Q4. What is meant by induced emf? By counter emf? A4. Induced emf is the emf which appears across a conductor when there is relative motion between the conductor and a magnetic field; counter emf is the emf induced in a conductor that opposes the applied voltage.

Q5. State Lenz's law. A5. The induced emf in any circuit is in a direction to oppose the effect that produced it. Q6. What effect does inductance have (a) on steady direct current and (b) on direct current while it is changing in amplitude? A6. (a) No effect. (b) Inductance opposes any change in the amplitude of current.

Q7. a. List five factors that affect the inductance of a coil. b. Bending a straight piece of wire into a loop or coil has what effect on the inductance of the wire? c. Doubling the number of turns in a coil has what effect on the inductance of the coil? d. Decreasing the diameter of a coil has what effect on the inductance of the coil? e. Inserting a soft-iron core into a coil has what effect on the inductance of the coil? f. Increasing the number of layers of windings in a coil has what effect on the inductance of the coil?

A7. (a) 1. The numbers of turns in a coil.

2. The type of material used in the core.

3. The diameter of the coil.

4. The coil length.

5. The number of layers of windings in the coil.

(b) Increases inductance.

(c) Increases inductance.

(d) Decreases inductance.

(e) Increases inductance.

(f) Increases inductance. Q8. a. When voltage is first applied to a series LR circuit, how much opposition does the inductance have to the flow of current compared to that of the circuit resistance? b. In a series circuit containing a resistor (R 1) and an inductor (L1), what voltage exists across R1 when the counter emf is at its maximum value? c. What happens to the voltage across the resistance in an LR circuit during current buildup in the circuit, and during current decay in the circuit? A8. a. Inductance causes a very large opposition to the flow of current when voltage is first applied to an LR circuit; resistance causes comparatively little opposition to current at that time.

b. Zero. c. During current buildup, the voltage across the resistor gradually increases to the same voltage as the source voltage; and during current decay the voltage across the resistor gradually drops to zero

Q9. What is the formula for one L/R time constant?

A9. R

Lt =

Q10. a. The maximum current applied to an inductor is 1.8 amperes. How much current flowed in the inductor 3 time constants after the circuit was first energized? b. What is the minimum number of time constants required for the current in an LR circuit to increase to its maximum value? c. A circuit containing only an inductor and a resistor has a maximum of 12 amperes of applied current flowing in it. After 5 L/R time constants the circuit is opened. How many time constants is required for the current to decay to 1.625 amperes?

A10. a. 1.71 amperes.

b. 5 time constants.

c. 2 time constants.

Q11. State three types of power loss in an inductor.

A11. Copper loss; hysteresis loss; eddy-current loss.

Q12. Define mutual inductance. A12. Mutual inductance is the property existing between two coils so positioned that flux from one coil cuts the windings of the other coil.

Q13. When are two circuits said to be coupled? A13. When they are arranged so that energy from one circuit is transferred to the other circuit.

Q14. What is meant by the coefficient of coupling? A14. The ratio of the fines of force produced by one coil to the lines of force that link another coil. It is never greater than one.

Q15. Two series-connected 7-H inductors are adjacent to each other; their coefficient of coupling is 0.64. What is the value of M?

A15. 4.48H (because 7H7HK M ×= = 0.64 x 7H = 4.48H)

Q16. A circuit contains two series inductors aligned in such a way that their magnetic fields oppose each other. What formula should you use to compute total inductance in this circuit?

A16. LT = L1 + L2 – 2M Q17. The magnetic fields of two coils are aiding each other. The inductance of the coils are 3 H and 5 H, respectively. The coils' mutual inductance is 5 H. What is their combined inductance?

A17. LT = 18H (because LT = 3H+ 5H + 2(5H) =18H)

INDUCTIVE AND CAPACITIVE REACTANCE

Q1. What effect does an inductor have on a change in current?

A1. An inductor opposes a change in current.

Q2. What is the phase relationship between current and voltage in an inductor? A2. Current lags voltage by 90° (ELI).

Q3. What is the term for the opposition an inductor presents to ac? A3. Inductive reactance.

Q4. What is the formula used to compute the value of this opposition? A4. XL = 2πfL.

Q5. What happens to the value of XL as frequency increases?

A5. XL increases.

Q6. What happens to the value of XL as inductance decreases?

A6. XL decreases.

Q7. What effect does the capacitor have on a changing voltage?

A7. The capacitor opposes any change in voltage.

Q8. What is the phase relationship between current and voltage in a capacitor? A8. Current leads voltage by 90° (ICE).

Q9. What is the term for the opposition that a capacitor presents to ac? A9. Capacitive reactance.

Q10. What is the formula used to compute the opposition?

A10. fC2π

1XC =

Q11. What happens to the valuce of XC as freqeuncy decreases?

A11. XC increases.

Q12. What happens to the value of XC as capacitance increases?

A12. XC decreases.

Q13. What is the formula for determining total reactance in a series circuit where the values of XC and XL are known? A13. X = XL – XC or X = XC - XL

Q14. What is the total amount of reactance (X) in a series circuit which contains an XL of 20 ohms and an XC of 50 ohms? (Indicate whether X is capacitive or inductive) A14. 30Ω (capacitive).

Q15. What term is given to total opposition to ac in a circuit?

A15. Impedance

Q16. What formula is used to calculate the amount of this opposition in a series circuit?

A16. 2X2RZ +=

Q17. What is the value of Z in a series ac circuit where XL = 6ohms, XC = 3ohms, and R = 4ohms? A17. Z = 5Ω

Q18. What are the Ohm's law formula used in an ac circuit to determine voltage and current?

A18. E = IZ Z

EI =

Q19. What is the true power in an ac circuit? A19. True power is the power dissipated in the resistance of the circuit or the power actually used in the circuit.

Q20. What is the unit of measurement of true power?

A20. Watt.

Q21. What is the formula for calculating true power?

A21. True Power = (IR)2R

Q22. What is the reactive power in an ac circuit? A22. Reactive power is the power returned to the source by the reactive components of the circuit.

NEETS Q&A

Q23. What is the unit of measurement of reactive power?

A23. var.

Q24. What is the formula for calculating reactive power?

A24. Reactive Power = (IX)2X

Q25. What is the apparent power? A25. The power that appears to the source because of circuit impedance, or the combination of the power and reactive power.

Q26. What is the unit of measurement of apparent power?

A26. VA (volt-amperes).

Q27. What is the formula for apparent power?

A27. Apparent power = (IZ)2Z or 22 power) (reactive power) (true +

Q28. What is the power factor of a circuit? A28. Power Factor is a number representing the portion of apparent power actually dissipated in a circuit. Q29. What is a general formula used to calculate the power factor of a circuit?

A29. cosθ PF or power reactive

power truePF ==

Q30. An ac circuit has a total reactance of 10 ohms inductive and a total resistance of 20 ohms. The power factor is 0.89. What would be necessary to correct the power factor to unity? A30. Add 10 ohms of capacitive reactance to the circuit.

Q31. What is the difference between calculating impedance in a series ac circuit and in a parallel ac circuit? A31. In a series circuit impedance is calculated from the values of resistance and reactance. In a parallel circuit, the values of resistive current and reactive current must be used to calculate total impedance.

INTRODUCTION TO COMMUNICATIONS THEORY

Q1. What are the four basic transmitter types?

A1. Am, fm, cw, ssb.

Q2. What is the function of the oscillator in a cw transmitter? A2. It generates an rf carrier at a given frequency within required limits.

Q3. What is the final stage of a transmitter?

A3. Power amplifier. Q4. What purpose does a microphone perform in an AM transmitter?

A4. It converts audio (sound) into electrical energy. Q5. In an fm transmitter, when does an oscillator generate only a steady frequency?

A5. When no modulation is present.

Q6. What is a harmonic?

A6. It is an exact multiple of the basic or fundamental frequency. Q7. If the fundamental frequency is 200 megahertz, what is the third harmonic?

A7. 600 megahertz.

Q8. Why are frequency multipliers used?

A8. To obtain higher carrier frequencies.

Q9. What are two advantages of ssb transmission?

A9. It saves power and frequency bandwidth.

Q10. What is the purpose of an order-wire circuit? A10. For operator-to-operator service messages and frequency changes.

Q11. What four basic functions must a receiver perform?

A11. Reception, selection, detection, and reproduction.

Q12. What are the four basic receiver characteristics?

A12. Sensitivity, noise, selectivity, and fidelity. Q13. What frequency conversion principle is used to develop the IF?

A13. Heterodyning.

Q14. What is the function of the detector?

A14. To extract the modulating audio signal. Q15. What is the major disadvantage of an fm signal as compared to an AM signal?

A15. Wide bandpass. Q16. What two components give a ssb receiver its advantages over an AM superheterodyne receiver?

A16. A special type of detector and a carrier reinsertion oscillator. Q17. What does manual gain control do to strong and weak signals, respectively?

A17. Attenuates the strong and amplifies the weak.

Q18. What is the purpose of agc/avc in a receiver?

A18. To limit unwanted variations in the output.

Q19. What is a disadvantage of agc? A19. Weak signals produce bias, which could result in no usable receiver output.

Q20. What is the main difference between agc and dagc?

A20. Dagc does not attenuate weak signals.

Q21. What is the function of the bfo?

A21. It is heterodyned with the rf to produce an audio frequency.

Q22. What is the purpose of a squelch circuit?

A22. It eliminates noise when no signal is being received. Q23. What does a tone control circuit in a receiver do to the audio signal?

A23. It controls the amount of bass and treble response.

Q24. What is the function of a crystal filter in a receiver?

A24. It is used to achieve maximum selectivity.

Q25. What is the primary function of an afc circuit?

A25. It is used to accurately control the frequency of the oscillator.

Q26. What is frequency synthesis? A26. The process of selecting and/or heterodyning frequencies to produce a signal frequency.

INTRODUCTION TO ELECTRON TUBES

Q1. How can a sheet of copper be made to emit electrons thermionically? A1. By heating it. Q2. Why do electrons cross the gap in a vacuum tube? A2. Because the negatively charged electrons are attracted to the positively charged plate.Q3. Name the two series circuits that exist in a diode circuit. A3. Filament and plate. Q4. Before a diode will conduct, the cathode must be what polarity relative to the plate?A4. Negative. Q5. An ac voltage is applied across a diode. The tube will conduct when what alternation of ac is applied to the plate?A5. Positive. Q6. What would be the output of the circuit described in question 5? A6. Pulsating dc. Q7. Besides tungsten, what other materials are used for cathodes in vacuum tubes?A7. Thoriated-tungsten and oxide-coated metals. Q8. What is the advantage of directly heated cathodes? A8. They reach operating temperatures quickly. Q9. Name two functions of the base of a vacuum tube. A9. It serves as a mounting for the tube elements and as the terminal connection to the circuit.Q10. Vacuum tubes are designed to operate in what portion of the Ep - Ip curve?A10. The linear portion. Q11. What value can be calculated from the values found on an Ep - Ip curve?A11. Plate resistant Rp. Q12. A large negative voltage is applied to the plate of a diode, and a large positive voltage is applied to the cathode. If what tube parameter has been exceeded? A12. Peak Inverse Voltage (PIV). Q13. What is the primary difference between a diode and a triode? A13. The triode contains a third element called the control rid. Q14. Why does the grid have a greater effect than the plate on electron flow through a vacuum tube?A14. Because it is closer to the cathode. Q15. What component is used in a triode amplifier to convert variation in current flow to voltage variation?A15. A plate load resistor RL Q16. Why the control grid of a triode amplifier is negatively biased? A16. To prevent them from drawing grid current. Q17. For a circuit to be considered to be in the quiescent condition, what normal operating voltage must be zero?A17. The input signal Q18. A triode amplifier similar to the one shown in figure 1-19 has an Ebb -350 conditions, 1.5 milliamperes of current conducts through the tube. What will be the plate voltage (Ep) under quiescent conditA18. +275 volts. Q19. A 2-volt, peak-to-peak, ac input signal is applied to the input of the circuit described in Q18. When the signal is at its maximum positive value, 2.5 milliamperes flows through the tube. When the input is at its maximum negative value, conduction through the tube .5 milliamperes. a. What is the peak-to-peak voltage of the output signal? b. What is the phase relationship between the input and output signals? A19. a. 100 volts. b. 180º out of phase. Q20. The waveforms shown below are the input and output of an overdriven triode.A20. a. Cutoff. b. Saturation. Q21. What type of bias requires constant current flow through the cathode circuit of a triode?A21. Cathode biasing. Q22. When a circuit uses cathode biasing, the input signal can cause variations in the biasing level HoA22. Through the use of a bypass capacitor Q23. In a circuit using grid-leak biasing, the coupling capacitor (Cc) charges through a low resistance path. What resistance is used in this charge path? A23. rkg, the cathode to grid resistance. Q24. Grid-leak biasing in effect rectifies the input ac signal. What feature of the circuit is used to accomplish this rectification?A24. Unequal charge and discharge paths of the coupling capacitor Cc. Q25. Match each amplifier characteristic listed below with its class of amplification.a. Current flows through the tube for one-half cycle. b. Current flows through the tube for less than one-half cycle. c. Current flows through the tube for the entire cycle.

NEETS Q&A

A25. a. Class B. b. Class C c. Class A Q26. The plate voltage of a tube will vary 126 volts when a 3-volt ac signal is applied to the control grid. What is the gain of this tube? A26. 42. Q27. If the mu of a tube is 85 and the signal at the control grid is 4 volts ac, the plate voltage will vary by what amount? A27. 340 volts. Q28. Transconductance is a measure of the relationship between what two factors? A28. The changes in plate current and grid voltage. Q29. A tube has a transconductance of 800 mhos and a load resistor of 50 kohms. When control grid voltage varies by 6 volts, the plate voltage will vary by what amount? A29. 240 volts. Q30. How does the addition of a screen grid in a tetrode reduce interelectrode capacitance? A30. The interelectrode capacitance (cpg) is divided between two series capacitances; thus, cpg is greatly reduced. Q31. What undesirable effect does the screen grid in a tetrode create? A31. Secondary emission, and noise. Q32. The suppressor grid is added to a tetrode to reduce what undesirable characteristic of tetrode operation? A32. Secondary emission. Q33. On the diagram below, name the elements of the vacuum tube and their potentials relative to dc ground. A33. a. Plate, positive. b. Suppressor grid, negative. c. Cathode, can be negative, positive, or at dc ground potential, depending on biasing type. d. Control grid, negative.

INTRODUCTION TO MAGNETIC RECORDING

Q-1. Why did the early inventors of magnetic recording find it necessary to add a fixed dc bias to the input signal? A-1. Because a step in the magnetism curve where it crosses the zero point and changes polarity causes the output signal to be distorted. See figure 1-1. Q-2. How does dc bias added to the input signal correct the distortion in the output signal? A-2. The dc bias moves the input signal away from the step in the magnetism curve. This prevents the input signal from crossing the zero-point of the magnetism curve. See figure 1-2. Q-3. Why does adding dc vice ac bias voltage to the input signal result in a poor signal-to-noise ratio (SNR)? A-3. With dc bias, the SNR is poor because only a small portion of the magnetism curve is straight enough to use, thus the output signal is weak compared with the natural tape hiss. Q-4. What are three advantages of adding an ac bias voltage to the input signal instead of adding a fixed dc bias voltage? A-4. a. Reproduces a stronger output signal. b. Greatly improves the SNR. c. Greatly reduces the natural tape hiss. Q-5. Why does using ac vice dc bias voltage result in a stronger output signal? A-5. Because an ac bias voltage of the proper frequency and level places the input signal away from both steps in the magnetism curve. The result is two undistorted output signals that are combined into one strong output. Q-6. What three things are required to perform magnetic recording? A-6. a. An input signal. b. A recording medium. c. A magnetic head. Q-7. What is the meaning of the term recording medium as it pertains to magnetic recording? A-7. A recording medium is any material that has the ability to become magnetized, in varying amounts, in small sections along its entire length. Q-8. What are the three functions of the magnetic heads on a magnetic recording device? A-8. a. Record the signal onto the recording medium. b. Reproduce the signal from the recording medium. c. Erase the signal from the recording medium.

INTRODUCTION TO RADIO-FREQUENCY COMMUNICATIONS

Q1. What are the two types of electrical communications?

A1. Radio and wire. Q2. What is the main advantage of radiotelegraph communications?

A2. Reliability. Q3. Why is radiotelephone one of the most useful methods of military communications?

A3. It is direct, convenient and easy to use. Q4. What are the disadvantages of radiotelephone communications?

A4. Static, enemy interference or a high local noise level.

Q5. What is the main use of a radio teletypewriter?

A5. High speed automatic communications across ocean areas.

Q6. What is facsimile? A6. The process used to transmit photographs, charts and other graphic information electronically.

Q7. A system is subdivided into what levels?

A7. Set, group, unit, assembly, subassembly, and part.

Q8. In the example 1A6CR3, what is the assembly designator?

A8. A6.

Q9. The majority of vlf transmitters are used for what purpose?

A9. Fleet communications or navigation. Q10. Today the Navy uses lf communications as a segment of what operational system?

A10. Fleet Multichannel Broadcast System. Q11. Why does the Navy only use the upper and lower ends of the mf band?

A11. Due to the commercial broadcast (AM) band. Q12. What are the four general types of communications services in the hf band?

A12. Point-to-point, ship-to-shore, ground-to-air, and fleet broadcast. Q13. A message transmitted on several frequencies at the same time is an example of what type of transmission?

A13. Frequency-diversity. Q14. Physically separating receive antennas is an example of what technique?

A14. Space-diversity. Q15. When using frequencies above 30 megahertz, you are normally limited to using what range?

A15. Line of sight. Q16. The naval communications system is made up of what two groups of communications?

A16. Strategic and tactical. Q17. What are the five most prominent communications modes of operation?

A17. Simplex, half-duplex, semiduplex, duplex, and broadcast. Q18. What four switched networks are part of the defense communications system?

A18. AUTOVON, AUTOSEVOCOM, AUTODIN, and DSSCS. Q19. What two elements support only designated Navy requirements?

A19. HICOM and NORATS.

INTRODUCTION TO SATELLITE COMMUNICATIONS

Q1. What are the two types of communications satellites?

A1. Passive and active. Q2. A typical satellite communications operational link consists of a satellite and what two other components?

A2. Earth terminals. Q3. A satellite in a synchronous orbit can cover how much of the surface of the earth?

A3. Approximately one-half. Q4. What areas of the earth are not normally covered by satellites?

A4. The extreme polar regions. Q5. What was the major operational limitation of early communications satellites?

A5. The lack of suitable power sources. Q6. Satellite orientation in space is important for what two reasons? A6. To allow maximum solar cell exposure to the sun and satellite antenna exposure to earth terminals.

Q7. What type of antennas are generally used at earth terminals?

A7. Large, high-gain parabolic antennas.

Q8. Why do earth terminals require highly sensitive receivers? A8. To overcome satellite transmitter low power and permit extraction of the desired information from the received signal. Q9. What is the range of earth terminal transmitter output power?

A9. Up to 20 kilowatts.

Q10. What is the function of shipboard receive-only equipment?

A10. To receive fleet multichannel tty broadcasts. Q11. What types of modulation are shipboard receive-only equipment designed to receive?

A11. Fm or psk.

Q12. Why is satellite acquisition and tracking important? A12. To ensure earth terminal antennas are always pointed towards the satellite. Q13. What are the two limitations to an active satellite communications system? A13. Satellite down-link transmitter power and up-link receiver sensitivity.

INTRODUCTION TO WAVEFORM INTERPRETATION

NEETS Q&A

Q-1. What is the result of overmodulating an AM signal?

A-1. Distortion. Q-2. For AM transmissions, the carrier is normally modulated within what range?

A-2. 60% to 95%.

Q-3. What is meant by frequency deviation? A-3. The difference between the carrier frequency of an fm signal and its maximum frequency excursion when modulated. Q-4. A spectrum analyzer is designed to display what signal characteristic? A-4. Amplitude versus frequency (the frequency domain of the signals). Q-5. What is the advantage of single-sideband (ssb) transmission over AM transmission? A-5. The same amount of intelligence can be transmitted with one-sixth of the output power with less than one-half the bandwidth. Q-6. What happens to an fm signal as you increase the frequency of the modulating signal? A-6. Both the bandwidth and the number of significant sidebands increase. Q-7. When referring to spectrum analyzers, what is meant by the term resolving signals? A-7. The ability of the analyzer to discriminate between display signals of slightly different frequencies. Q-8. Why are time-domain reflectometers often compared to a radar system?

A-8. Both transmit a pulse and analyze the signal reflection. Q-9. What is the main advantage of using a time-domain reflectometer (tdr) to test a transmission line? A-9. A Tdr will indicate the nature of and the distance to or location of any faults.

Q-10. What is the purpose of swept-frequency testing? A-10. To determine various characteristics of a component, piece of equipment, or system over its operational frequency range. Q-11. In swept-frequency testing the impedance of a transmission line, what electrical characteristic is actually being measured?

A-11. Swr on the transmission line. Q-12. What precautions must be taken when sweeping a transmitting antenna? A-12. You must ensure that power induced from any adjacent transmitting antennas does not damage your test equipment.

MAGNETIC DISK RECORDING

Q1. Floppy disks are manufactured in what three sizes?

A1. 8 inch, 5 1/4 inches, 3 1/2 inches. Q2. What type of floppy disk is made to store data on both sides of the disk?

A2. Double-sided.

Q3. What are the three levels of floppy disk density? A3. a. Single-density, b. double-density, and c. high-density. Q4. What is the storage capacity of a 5-1/4" double-sided, high-density floppy disk?

A4. 1,200,000 bytes or 1.2 megabytes. Q5. The floppy disks you are using have a rating of 96 TPI. What does this mean?

A5. The disks can hold 96 tracks per inch. Q6. The process of formatting a floppy disk is called what type of sectoring?

A6. Soft sectoring. Q7. What three components determine the address that locates where on a floppy disk the computer will store the data? A7. a. disk side number, b. track number, and c. sector number. Q8. Why should you always store floppy disks in their envelopes? A8. Dust and other contaminates can get on the recording surface through the read/write hole. Q9. Why should you never place floppy disks near telephones or other electronic equipments that generate magnetic fields?

A9. Magnetic fields can destroy the data on a disk.

Q10. What are the two ways to erase floppy disks? A10. a. Degauss the disk and then reformat it. b. Reformat the disk. Q11. What are the three most common sizes of hard disk platters?

A11. 3-1/2 inches, 5-1/4 inches, and 14 inches. Q12. Computers use what two methods to place data on a hard disk?

A12. (1) Cylinder method and (2) sector method. Q13. Which method for placing data on hard disks divides a hard disk into pie shaped slices?

A13. Sector method. Q14. When computers use the cylinder method to store data on a hard disk pack, what three items make up the address that tells the computer where on a specific disk to store the data? A14. a. Cylinder number. b. Recording surface number. c. Record number.

Q15. What is the most common type of hard disk failure?

A15. Head-crash. Q16. Hard disks should be stored in an environment that stays within what relative humidity and temperature range? A16. a. 30-60 percent relative humidity. b. 70-80 degrees Fahrenheit.

Q17. What is the most common method for erasing a hard disk?

A17. Reformat the disk. Q18. What are the three most popular methods for encoding digital data onto magnetic disks? A18. a. Frequency modulation (FM). b. Modified frequency modulation (MFM). c. Run length limited (RLL). Q19. Older, single-sided, single-density floppy disk drives would probably use what method for encoding digital data onto the floppy disk?

A19. Frequency-modulation encoding. Q20. What method for encoding digital data enables you to store more data in less space by limiting the distance between pulses on a hard disk?

A20. Run length-limited (RLL) encoding. Q21. What are the four most important parts of a floppy disk drive transport? A21. a. Drive motor/spindle assembly. b. Head arm assembly. c. Actuator arm assembly. d. Drive electronics circuit board. Q22. The drive motor of a 3-1/2", 1.44-MB floppy disk drive spins the disk at what RPM?

A22. 600 RPM. Q23. The head arm assembly of a floppy disk drive transport has how many read heads and how many write heads?

A23. Two read heads and two write heads. Q24. What part of a floppy disk drive transport uses a dc stepper motor to position the magnetic heads over the recording surface of a floppy disk?

A24. Actuator arm assembly. Q25. What part of a floppy disk drive transport contains the circuitry which controls the electromechanical parts of the transport?

A25. Drive electronics circuit board. Q26. Hard disk drive transports contain the electromechanical parts that perform what three functions? A26. a. Rotates the hard disk platters. b. Writes data to and reads data from the disk platters. Q27. In the actuator arm assembly of a hard disk drive transport, what device can position the magnetic heads to the correct track of a hard disk more accurately than a dc stepper motor?

A27. Voice coil servo. Q28. Why do floppy disk drives require more preventive maintenance than hard disk drives? A28. They are not sealed units, and they use flimsy plastic disks with an oxide coating that wears off and sticks to the heads. Q29. A kit for cleaning floppy disk drives contains what two items? A29. a. A cloth or fiber cleaning disk. b. A bottle of cleaning solution. Q30. Approximately how often should you clean a floppy disk drive that gets heavy use?

A30. Once a month Q31. Cartridge hard disk drives with 14" disk packs may require what additional types of preventive maintenance? A31. a. Cleaning with a special cleaning disk. b. Cleaning air filters. c. Cleaning spindles, rails, and slides. d. Cleaning and buffing read/write heads. Q32. The control electronics component of a floppy or hard disk drive performs what three main functions? A32. a. Spins the disk at the correct speed. b. Moves the heads across the recording surface. c. Tells the write/read heads when to write data and when to read it. Q33. The write/read electronics of a disk drive performs what three functions?

A33. a. Formats and writes incoming data from the interface

NEETS Q&A

electronics onto the disk. b. Reads data off the disk, formats it, and sends it to the interface electronics for output. c. Performs the initial disk formatting. Q34. The interface electronics of a disk drive performs what three functions? A34. a. Receives control signals from the host computer and sends them to the control electronics or write/read electronics. b. Receives data from the write/read electronics and outputs it to the host computer. c. Converts incoming and outgoing data from parallel to serial, and vice versa, if needed. Q35. What type of interface electronics is used in many naval electronic warfare systems?

A35. NTDS interface. Q36. What type of disk drive interface has most of the electronics on a controller card mounted in the host computer?

A36. ST-506/412 interface. Q37. The SCSI is a high level disk drive interface. What does this mean? A37. The host computer asks for data by specifying a logical sector number. The SCSI translates the sector number into the actual disk location. Q38. What type of hard disk drive interface has all of the controller card electronics included in the disk drive itself?

A38. Integrated drive electronics (IDE).

MAGNETIC TAPE

Q-1. Magnetic tape is made of what three basic materials? A-1. a. Base material. b. Coating of magnetic oxide particles. c. Glue that bonds the particles to the base.

Q-2. Why is plastic magnetic tape used more than metal tape? A-2. Plastic tape is used more than metal because it’s more flexible, resists mildew and fungus, and is very stable at high temperatures and humidity. Q-3. Which of the two types of magnetic tape is used to record audio and instrumentation type signals in the VLF to 2.5MHz frequency range?

A-3. Analog magnetic tape. Q-4. What type of magnetic tape is used to record computer programs and data, and what are the additional thickness and quality standards for this type of tape? A-4. Digital magnetic tape is for computer programs and data. Its base material is about 50% thicker. The tape’s surface must not have blemishes or coating flaws because losing even one digital data bit could ruin the recorded computer program or data. Q-5. What are four types of tape errors that can degrade a magnetic recording system’s performance? A-5. Signal dropout, noise, skew, and level. Dropout is the most common. Q-6. What are signal dropouts, and what are two tape defects that can cause signal dropouts? A-6. Dropouts are temporary, sharp drops (50% or more) in signal strength. They’re caused by contaminates that lift the tape away from the magnetic head, or when magnetic oxide coating is missing on part of the tape. Q-7. What is the most common and most serious type of signal dropout?

A-7. Oxide particles that get onto the magnetic tape. Q-8. You see a build-up of dust and lint on the take-up reel of a tape recorder. This can cause which of the four types of tape errors? A-8. Signal dropout errors and level errors. The dust and lint on the reel will eventually get onto the tape where it can get between the tape and the recorder’s heads. Q-9. What type of tape error causes noise to appear on the tape when no signal should appear? What causes this type of tape error? A-9. Noise error is usually caused by a cut or a scratch on the magnetic tape. Q-10. The multi-track tape recorder in your computer system has a fixed skew error. What does this mean and what is the probable cause? A-10. Skew means there are time differences between the individual tracks of a multi-track recorder’s magnetic head. It happens when the tape isn’t properly aligned with the head. Fixed skew happens when the tape passes over an improperly aligned magnetic head. Q-11. Some tapes you are using may have level errors. What does this mean and what is the cause? A-11. The actual output signal level of the tape exceeds the manufacturer’s specified range for the output signal level (+ / - 10%). It’s caused by an uneven oxide coating on the tape due to worn tape or defective manufacture.

Q-12. What is tape failure?

A-12. Tape’s performance degrades to a point where it’s no longer

usable.

Q-13. What are four main causes of tape failure? A-13. Normal wear, accidental damage, environmental damage, and winding errors.

Q-14. How does normal wear cause tape failure? A-14. Repeated contact with a recorder’s fixed surfaces such as magnetic heads, tape rollers, and tape guides. Q-15. Accidental damage to magnetic tape is normally caused by the tape recorder itself or by human operators of the recorder. What are three frequent causes of such accidental damage? A-15. a. Improperly adjusted tape transport mechanism. b. Dropping a reel of tape. c. Improperly threading tape. Q-16. Environmental damage to magnetic tape can occur when the tape is stored in an area that exceeds what ideal temperature and humidity ranges? A-16. Ideally, use and store tape at 60 to 80º F and at 40 to 60% relative humidity. Q-17. What six types of environmental damage can occur to tapes in storage when the ideal temperature and humidity ranges are exceeded? A-17. Tape deformation, oxide shedding, head-to-tape sticking, layer-to-layer sticking, dirt build-up, and excessive tape and head wear.

Q-18. After using a tape that was stored in an area where temperatures exceeded 130º F you notice pieces of oxide sticking to the recorder's tape-transport mechanism, to its magnetic heads, and onto the tape. What is the probable cause of these symptoms? A-18. Oxide shedding. At temperatures above 130º F, oxide coating becomes soft and sheds. Q-19. Your activity stores its magnetic tape in an area where the temperature is 100º F. What two types of environmental damage could occur that would make these tapes unusable?

A-19. Head-to-tape sticking and layer-to-layer adhesion. Q-20. When the relative humidity is below 10%, what happens to magnetic tape and parts of a tape recorder that could cause environmental damage?

A-20. Dirt build-up caused by static electricity. Q-21. How does relative humidity over 95% cause excessive tape and head wear? A-21. High humidity causes increased friction as the tape passes over the heads. Q-22. Tape winding errors can cause a deformed tape pack. What are four common types of tape pack deformation?

A-22. Cinching, pack slip, spoking, and windowing. Q-23. After rewinding a tape onto its supply reel, you examine the tape pack and notice pile-ups of tape resembling the example in figure 2-2. What causes this condition?

A-23. The tape is stopped too quickly when winding or rewinding. Q-24. You notice steps in the tape pack such as those in figure 2-3. What causes this and how does it damage the magnetic tape? A-24. Pack slip. It's caused by loosely wound tape on a reel that is exposed to excessive vibration or heat. The vibration or heat causes the tape to shift, causing steps in the tape pack. The uneven tape will then rub against the reel's sides and the recorder's tape guides. Q-25. A tape pack is buckled and deformed as shown in figure 2-4. What are three possible causes for this condition? A-25. a. Reel has a distorted hub, b. tape wound over small particle deposited on hub, and c. tape wound on reel with tension increasing toward end of winding. Q-26. A tape pack has gaps in the tape winding as shown in figure 2-5. What causes this condition?

A-26. Tape is loosely wound on reel. Q-27. When winding a tape onto a plastic or metal reel, should the tape ever touch the reel’s flanges? A-27. No. The reel is designed to hold the tape on its hub without letting the tape touch the sides of the flanges. Q-28. What are two disadvantages of using a recorder’s erase head to erase data recorded on a magnetic tape? A-28. Using an erase head is slow, and it may not completely erase the tape. Q-29. What method for erasing magnetic tape is much more effective and reliable than using a recorder’s erase head?

A-29. Using a magnetic tape degausser. Q-30. When magnetic tapes are ruined, what three factors are normally the cause?

A-30. Poor handling, improper storage, or shipping damage.

Q-31. What is the correct way to hold a magnetic tape reel?

NEETS Q&A

A-31. Always hold reel by the hub, never by the flanges. Never touch the working tape surface. Q-32. The take-up reel on your recorder is warped. What should you do to/with the reel?

A-32. Always replace a warped reel. Q-33. If magnetic tape is stored in areas with temperature and humidity extremes, what are three types of tape damage that may occur?

A-33. Oxide shedding, layer-to-layer sticking, and tape deformation. Q-34. List four rules you should follow when storing magnetic tape to protect it from damage. A-34. a. Make sure the tape is wound properly on the reel hub, b. store tapes vertically, c. keep storage area at right temperature and humidity, d. store away from equipment that generates stray magnetic fields. Q-35. When packaging tape reels or cartridges for shipping, what are four rules you should follow to protect the tape reels from impact and vibration? A-35. a. Package reels so they’re supported by their hub, b. use reel bands, c. package reels in vertical position, d. package tape cartridges in their shipping cases.

MAGNETIC TAPE RECORDER HEADS

Q-1. Magnetic tape recorders can have up to three different heads installed. What are the three functions performed by a recorder's heads?

A-1. Record, reproduce, and erase. Q-2. The way a magnetic head will be used determines how it is constructed. Name three factors that determine the final construction of a magnetic head. A-2. a. Type of head (record, reproduce, or erase). b. Frequencies it will record or reproduce. c. Whether it will be used on a single or multitrack recorder. Q-3. What two specifications determine the maximum frequency that a recorder's record and reproduce heads will be able to transfer? A-3. a. Size of the headgap. b. Speed of the magnetic tape. Q-4. Most record and reproduce heads are in one of what three bandwidth categories? A-4. a. Narrowband—100 Hz to 100 kHz. b. Intermediate band—100 Hz to 500 kHz. c. Wideband—400 Hz to 2 mHz. Q-5. Why are record heads always placed before reproduce heads on recorders?

A-5. Allow you to monitor the signals you're recording. Q-6. A recorder's erase head is always placed in what sequence on the record/reproduce track?

A-6. First, before the record and reproduce heads. Q-7. What two preventive maintenance actions must you do regularly to increase magnetic head life and to ensure good tape recording and playback? A-7. a. Keep the heads clean. b. Keep the heads demagnetized.

Q-8. How should you clean your recorder's magnetic heads? A-8. With a cotton-tipped applicator soaked in either isopropyl alcohol or a head cleaner recommended by the recorder's manufacturer. Q-9. What are four sources that can cause magnetic heads to become magnetized? A-9. a. During ac power losses. b. During testing. c. Because of stray magnetic fields. d. From normal use. Q-10. What type of equipment should you use to demagnetize your recorder's magnetic heads? A-10. A hand-held degausser like the manual degaussers used for degaussing magnetic tape. Q-11. How often should you demagnetize a recorder's magnetic heads? A-11. Every 8 to 25 hours depending on the manufacturer's recommendations.

MAGNETIC TAPE RECORDER RECORD AND REPRODUCE

ELECTRONICS

Q-1. What two types of record and reproduce electronics are used by magnetic tape recorders? A1. a. Direct record (AM). b. Frequency modulation (FM).

Q-2. The head driver circuit in a tape recorder’s direct record electronics component (figure 5-1) performs what function? A2. It takes the signal from the summing network, amplifies it, and sends it to the record head for recording. Q-3. The equalization and phase correction circuit in a tape recorder’s direct reproduce electronics (figure 5-2) performs what function? A3. It generates an equalization signal which corrects any frequency response problems in the input signal from the pre-amplifier circuit. Q-4. How do FM record electronics differ from AM (direct record) electronics? A4. Instead of recording the signal just as it appears at the recorder’s input, FM record electronics records a frequency-modulated carrier signal from a record oscillator (figure 5-4) onto the magnetic tape. Q-5. The head driver circuit of a tape recorder’s FM record electronics (figure 5-4) performs what function? A5. It amplifies the frequency-modulated output from the record oscillator and sends it to the record head. Q-6. What is the major difference between direct reproduce electronics and FM reproduce electronics? A6. FM record electronics must use a limiter and demodulator circuit (figure 5-5) to demodulate the signal intelligence from the carrier frequency.

MAGNETIC TAPE RECORDING SPECIFICATIONS

Q-1. Two tape recorders have signal-to-noise ratios (SNRs) of 25-dB RMS and 35-dB RMS respectively. Which of the SNRs can record and reproduce the widest range of input signals and why? A1. 35-dB RMS because the highest SNR can always record and reproduce the widest range of input signals. Q-2. You plan to measure your tape recorder’s SNR. What test equipment will you need?

A2. A VTVM and a signal generator. (See figure 6-1.) Q-3. Technical manuals for tape recorders can state the SNR in what three different ways? A3. a. Root-mean-square (RMS) signal-to-RMS noise. b. Peak-to-peak signal-to-RMS noise. c. Peak signal-to-RMS noise. Q-4. The frequency-response specification of your tape recorder reads within +/ - 3 dB from 150 Hz to 150 kHz at 60 ips. What does this mean? A4. The recorder can record all frequencies between 150 Hz and 150 kHz at 60 ips without varying the output amplitude more than 3 dB. Q-5. While measuring frequency response, as the signal generator approaches the lowest and highest frequency the recorder can effectively record, the VTVM reading drops to less than - 3 dB. What does this indicate? A5. The upper and lower limits of the frequency response specification for that tape recorder. Q-6. List four factors that can degrade the frequency response of magnetic tape recorders. A6. a. A too-high or too-low bias signal level setting for the record head. b. An improper reproduce head gap. c. An improper tape transport speed. d. Poor tape-to-head contact. Q-7. A recorder’s harmonic-distortion specification reads 2% third harmonic of a 100-kHz signal at 60 ips. What does this mean? A7. The recorder has 2% third-harmonic distortion of a 100-kHz signal at 60 ips.

Q-8. What are three possible causes of even-order harmonics? A8. a. Permanently magnetized heads. b. Faulty circuitry. c. Asymmetrical bias signal. Q-9. What number harmonic is the primary harmonic distortion in magnetic tape recorders?

A9. Third-order harmonic. Q-10. When measuring harmonic distortion, you set the signal generator to input a 15-kHz test signal. To what frequency should you set the wave analyzer?

A10. 45 kHz. Q-11. How should a tape recorder with good phase response reproduce a complex waveform, such as a square wave?

A11. With no distortion. Q-12. How could you check the phase response of a tape recorder? A12. Record and reproduce a square wave and see if the output on an oscilloscope is symmetrical.

Q-13. What causes flutter in a tape recorder’s output?

A13. Non-uniform tape motion caused by variations in tape speed.

Q-14. What causes low-frequency flutter (below 1000 Hz)? A14. Rotating parts of a tape transport, such as irregular tape reels, sticking guides and pinch rollers, and capstans.

Q-15. What causes high-frequency flutter (above 1000 Hz)?

A15. Fixed parts of a tape transport, such as fixed tape guides and

NEETS Q&A

magnetic heads.

Q-16. Your recorder’s TBE specification reads " +/ - 80 microseconds over a 10 millisecond time interval at a tape speed of 60 ips, referenced to a control tone." What does this mean? A16. The TBE could cause a signal to jitter +/ - 80 microseconds over a 10-millisecond period at a tape speed of 60 ips. Q-17. Why is it important to minimize TBE jitter in magnetic tape recordings where precise timing relationships exist between two or more signals?

A17. The jitter could cause noise and a loss of accuracy. Q-18. The skew specification of your multi-tracked tape recorder reads " +/ - 0.20 microseconds between adjacent tracks on the same head stack at 120 ips." What does this mean? A18. One of the tracks on a magnetic head could lead or lag the track next to it by as much as 0.20 microseconds at 120 ips.

Q-19. How can you minimize fixed skew?

A19. Adjust the recorder’s electronics or realign the magnetic heads.

Q-20. When are fixed skew errors most likely to show up? A20. When you record on one tape recorder and then reproduce on a different recorder. Q-21. How do worn or sticking tape transport guides cause dynamic skew on a multi-track recorder?

A21. The tape drifts past the multi-track head at an angle.

MAGNETIC TAPE RECORDER TRANSPORTS

Q-1. What are the four basic parts of a magnetic tape recorder's tape transport system? A1. a. Tape reeling system. b. Tape speed control system. c. Electronic subsystem. d. Basic enclosure. Q-2. What are the three most commonly used tape reeling systems? A2. a. Take-up control. b. Two-motor reeling. c. Tape buffering. Q-3. What are two disadvantages of the take-up control reeling system? A3. a. It only works in one direction. b. The tape tension varies as the supply reel unwinds, which can cause damage during starts and stops. Q-4. What are two advantages of a two-motor reeling system over a take-up control reeling system? A4. The two-motor configuration runs in both directions and a holdback voltage helps control tape tension, but it does not properly control tape tension during starts and stops. Q-5. What type of reeling system best controls a tape recorder's tape tension during starts and stops?

A5. A tape buffering reeling system. Q-6. What are the two basic types of tape buffering reeling systems? A6. a. Spring-tension buffering systems. b. Vacuum-column buffering systems. Q-7. How do the tape guides on a tape reeling system protect the tape from damage during operation? A7. They keep the tape straight with respect to both the supply and take-up reels and the magnetic heads. Q-8. There are two types of tape transport configurations, open-loop capstan drive and closed-loop capstan drive. What are two major disadvantages of open-loop capstan drive tape transports? A8. a. Only operates in one direction. b. The tape tension and head-to-tape contact can vary. Q-9. How do closed-loop capstan drive tape transports overcome the disadvantages of the open-loop drive design? A9. Closed loop capstan drive transports use more than one capstan to clamp the tape in the area around the magnetic head. Q-10. What are the three most common closed-loop capstan drive designs? A10. a. Differential velocity capstans. b. Dual motors dual capstans. c. Peripheral drive capstans. Q-11. How do tape transports with differential velocity capstans maintain a constant tape tension in the area around the magnetic heads? A11. The supply capstan is slightly larger than the take-up capstan. This causes the take-up capstan to pull the tape slightly faster than the supply capstan feeds the tape. Q-12. How do dual-motor dual capstan drives maintain a constant tape tension while operating in either a forward or reverse direction? A12. Each capstan is driven by its own motor. It maintains tape tension by slowing down one of the motors. When the tape motion is reversed, the opposite motor is slowed down. Q-13. What are the two critical functions of the capstan speed control part of a magnetic tape transport system?

A13. Makes sure the capstan turns at the right speed and at a constant speed. Q-14. Which part of the capstan speed control function monitors the true capstan motor speed?

A14. Capstan speed monitor. Q-15. Sometimes it's necessary, but why should you avoid using cotton swabs when cleaning a magnetic tape transport?

A15. Cotton swabs are not lint free. Q-16. When cleaning the parts of a tape transport, why should you switch lint-free cloths and swabs often? A16. You may transfer dirt or oxide particles from one part of the tape transport to another. Q-17. What equipment should you use to de-magnetize a magnetic tape transport?

A17. A hand-held degausser.

MATTER, ENERGY, AND ELECTRICITY

Q1. What is matter, and in what three states is it found? A1. Anything that occupies space and has weight. Solids, liquids, gases.

Q2. What is an element? A2. A substance which cannot be reduced to a simpler substance by chemical means.

Q3. What is a compound? A3. A substance consisting of two or more elements.

Q4. What is the difference between a compound and a mixture? A4. A compound is a chemical combination of elements that cannot be separated by physical means. A mixture is a physical combination of elements and compounds that are not chemically combined.

Q5. What is a molecule? A5. A chemical combination of two or more atoms. Q6. What are the three types of subatomic particles, and what are their charges? A6. Electrons-negative, protons-positive, and neutrons-neutral.

Q7. What is energy of motion called? A7. Kinetic energy. Q8. How is invisible light changed to visible light in a fluorescent light? A8. Invisible light photons (ultraviolet) bombard the phosphor atom in the light tube. The phosphor atoms emit visible light photons.

Q9. What determines the valence of an atom? A9. The number of electrons in the outer shell.

Q10. What is an ion? A10. An atom with more or less than its normal number of electrons. Q11. What determines whether a substance is a conductor or an insulator? A11. The number of valence electrons.

Q12. How is a negative charge created in a neutral body? A12. Through the accumulation of excess electrons.

Q13. How are static charges created? A13. By friction. Q14. What is the electrical charge of an atom which contains 8 protons and 11 electrons? A14. Negative.

Q15. What is the relationship between charged bodies? A15. Like charges repel, and unlike charges attract with a force directly proportional to the product of their charges and inversely proportional to the square of the distance between them.

Q16. What is an electrostatic field? A16. The space between and around charged bodies.

Q17. In what direction are electrostatic lines of force drawn? A17. Leaving positive, entering negative. Q18. What are some examples of electrical equipment which use magnetism? A18. Motors, generators, speakers, computers, televisions, tape recorders, and many others.

Q19. What are magnetic materials? A19. Those materials that are attracted by magnets and have the ability to become magnetized. Q20. What characteristics do all ferromagnetic materials have in common? A20. The relative ease with which they are magnetized. Q21. What type of magnetic material should be used to make a temporary magnet? A21. A material that exhibits low reluctance and high permeability, such as iron or soft steel.

Q22. What is retentivity? A22. The ability of a material to retain magnetism. Q23. How does the law of magnetic poles relate to the law of electric charges? A23. They are very similar; like charges repel, unlike charges attract, like poles repel —unlike poles attract.

NEETS Q&A

Q24. A compass is located at the geographical North Pole. In which direction would its needle point? A24. To the magnetic north pole. Q25. Using Weber’s molecular theory of magnetism, describe the polarity of the magnetic poles produced by stroking a magnetic material from right to left with the south pole of a magnet. A25. South pole at the right, north pole at the left. Q26. What is the difference between the domain theory and Weber’s theory of magnetism? A26. The domain theory is based upon the electron spin principle; Weber’s theory uses the concept of tiny molecular magnets. Q27. Refer to figure 1-13. For what purpose would you sprinkle iron filings on the glass plate? A27. To enable you to "see" the magnetic field. Q28. Refer to figure 1-13. What pattern would be formed if sawdust was sprinkled on the glass instead of iron filings? A28. No specific pattern, sawdust is a nonmagnetic material.

Q29. What is a magnetic line of force? A29. An imaginary line used to illustrate magnetic effects. Q30. In what way do magnetic lines of force differ from electrostatic lines of force? A30. Electrostatic lines of force do not form closed loops. Q31. How should a delicate instrument be protected from a magnetic field? A31. By shielding or surrounding the instrument with a soft iron case, called a magnetic shield or screen.

Q32. How should bar magnets be stored? A32. In pairs, with opposite poles together to provide a complete path for magnetic flux.

Q33. What is the definition of energy? A33. The ability to do work.

Q34. What type of energy does a rolling stone have? A34. Kinetic energy. Q35. What kind of energy does the stone have if it is at rest at the top of a hill? A35. Potential energy.

Q36. What term describes voltage or emf? A36. Difference of potential.

Q37. Convert 2.1 kV to volts. A37. 2100 volts. Q38. Express the following in more simple terms. (a) 250,000 volts, (b) 25,000,000 microvolts, (c) 0.001 millivolt. A38. (a) 250 kV, (b) 25 V, (c) 1µV Q39. A device which supplies a voltage is commonly referred to by what name? A39. A voltage source.

Q40. Name the six methods of producing a voltage. A40. Friction, pressure, heat, light, chemical action, and magnetism. Q41. The piezoelectric effect is an example of a voltage being produced by what method? A41. Pressure. Q42. A thermocouple is a device that produces voltage by what method? A42. Heat.

Q43. A battery uses what method to produce a voltage? A43. Chemical.

Q44. A generator uses what method to produce a voltage? A44. Magnetic. Q45. According to electron theory, an electric current flows from what potential to what potential? A45. Electron theory assumes that electron flow is from negative to positive. Q46. The effects of directed drift take place at what rate of speed? A46. The speed of light (186,000 miles per second, 300,000,000 meters per second).

Q47. What is the relationship of current to voltage in a circuit? A47. Current increases as voltage increases.

Q48. Convert 350 mA to amperes. A48. 0.35 amperes.

Q49. What is the symbol for ohm? A49. Ω Q50. When would silver be used as a conductor in preference to copper? A50. When the need for conductivity is great enough to justify the additional expense. Q51. Which wire has the least resistance? Wire A-copper, 1000 circular mils, 6 inches long. Wire B-copper, 2000 circular mils, 11 inches long. A51. Wire B. Q52. Which temperature coefficient indicates a material whose resistance increases as temperature increases?

A52. Positive. Q53. What term describes a material whose resistance remains relatively constant with changes in temperature? A53. Zero temperature coefficient. Q54. What is the unit of conductance and what other term is sometimes used? A54. The mho (v), siemens. Q55. What is the relationship between conductance and resistance? A55. They are reciprocals of each other.

Q56. What is schematic symbol for a resistor? A56.

Q57. What does the wattage rating of a resistor indicate? A57. Its ability to dissipate heat.

Q58. What are the two disadvantages of carbon-type resistors? A58. 1. Change value with age. 2. Limited power capacity. Q59. What type resistor should be used to overcome the disadvantages of the carbon resistor? A59. The wirewound resistor. Q60. Describe the differences between the rheostat connections and those of the potentiometer. A60. The rheostat may have two connections, one fixed and one moveable; the potentiometer always has three connections, one moveable and two fixed. Q61. Which type of variable resistor should you select for controlling a large amount of current? A61. The rheostat. Q62. A carbon resistor has a resistance of 50 ohms, and a tolerance of 5 percent. What are the colors of bands one, two, three, and four, respectively? A62. The bands are green, black, black, and gold. Q63. A carbon resistor has the following color bands: The first band is yellow, followed by violet, yellow, and silver. What is the ohmic value of the resistor? A63. 470,000 ohms (470 kilo ohms). Q64. The same resistor mentioned in question 63 has a yellow fifth band. What does this signify? A64. The resistor’s chance of failure is 0.001 percent for 1000 hours of operation. Q65. A resistor is handed to you for identification with the following color code: the first band is blue, followed by gray, green, gold, and brown. What is the resistor’s value? A65. 6,800,000 ohms (6.8 mega ohms), with 5% tolerance, and a 1% reliability level.

MICROELECTRONICS

Q1. What problems were evident about military electronic systems during World War II?

A1. Size, weight, and power consumption.

Q2. What discovery opened the door to solid-state electronics?

A2. The transistor and solid-state diode.

Q3. What is microelectronics? A3. Technology of electronic systems made of extremely small electronic parts or elements. Q4. What discovery proved to be the foundation for the development of the vacuum tube?

A4. The Edison Effect. Q5. Name the components which greatly increase the weight of vacuum-tube circuitry.

A5. Transformers, capacitors, and resistors.

Q6. What are the disadvantages of point-to-point wiring? A6. "Rat's nest" appearance and unwanted interaction, such as capacitive and inductive effects.

Q7. What is a major advantage of modular construction?

A7. Rapid repair of systems and improved efficiency. Q8. When designing vacuum-tube circuits, what characteristics of tubes must be taken into consideration?

A8. Differences in performance of tubes of the same type.

Q9. List the major advantages of printed circuit boards.

A9. Eliminate heavy chassis and point-to-point wiring.

Q10. What is the major disadvantage of printed circuit boards?

A10. Components soldered in place. Q11. The ability to place more components in a given space is an advantage of the _______.

A11. Cordwood module.

Q12. Define integrated circuit. A12. Elements inseparably associated and formed in or on a single substrate.

Q13. What are the three major types of integrated circuits?

NEETS Q&A

A13. Monolithic, film, and hybrid.

Q14. How do monolithic ICs differ from film ICs? A14. Monolithic ICs contain active and passive elements. Film ICs contain only passive elements.

Q15. What is a hybrid IC?

A15. Combination of monolithic ICs and film components.

Q16. How many logic gates could be contained in lsi?

A16. 1,000 to 2,000.

Q17. What are the basic steps in manufacturing an IC? A17. Circuit design, component placement, suitable substrate, and depositing proper materials on substrate.

Q18. Computer-aided layout is used to prepare _______ devices.

A18. Complex.

Q19. What purpose do masks serve?

A19. Control patterns of materials on substrates.

Q20. What type of substrates is used for film and hybrid ICs?

A20. Glass or ceramic.

Q21. Describe the preparation of a silicon substrate. A21. Crystal is sliced into wafers. Then ground and polished to remove any surface defect. Q22. Name the two types of monolithic IC construction discussed.

A22. Diffusion; epitaxial growth.

Q23. How do the two types of monolithic IC construction differ?

A23. Diffusion penetrates substrate; epitaxial does not.

Q24. What is isolation?

A24. Electrical separation of elements. Q25. What methods are used to deposit thin-film components on a substrate?

A25. Evaporation and cathode sputtering.

Q26. How are thick-film components produced?

A26. Screening.

Q27. What is a hybrid IC?

A27. Combination of monolithic and film elements.

Q28. What is the primary advantage of hybrid circuits?

A28. Circuit flexibility.

Q29. What is the purpose of the IC package?

A29. Protect the IC from damage; make handling easier.

Q30. What are the three most common types of packages?

A30. TO, flat pack, DIP. Q31. What two methods of manufacture are being used to eliminate bonding wires?

A31. Flip-chip, beam lead. Q32. On DIP and flat-pack ICs viewed from the top, pin 1 is located on which side of the reference mark?

A32. Left. Q33. DIP and flat-pack pins are numbered consecutively in what direction?

A33. Counterclockwise. Q34. DIP and flat-pack pins are numbered consecutively in what direction?

A34. Reference mark. Q35. Viewed from the bottom, TO-5 pins are counted in what direction?

A35. Clockwise. Q36. The numbers and letters on ICs and schematics serve what purpose?

A36. Identify the type of IC. Q37. Standardized terms improve what action between individuals?

A37. Communication. Q38. Microcircuit refers to any component containing what types of elements?

A38. Integrated circuits. Q39. Components made up exclusively of discrete elements are classified as what type of electronics?

A39. Miniature. Q40. Resistors, capacitors, transistors, and the like, are what level of packaging?

A40. Level 0. Q41. Modules or submodules attached to a mother board are what packaging level?

A41. Level I.

Q42. What is the packaging level of a pcb?

A42. Level II. Q43. What are the three most common methods of interconnections? A43. Conventional printed circuit boards, multilayer printed circuit boards and modular assemblies. Q44. Name the three methods of interconnecting components in multilayer printed circuit boards.

A44. Clearance hole, plated-through hole, and layer build-up. Q45. What is one of the major disadvantages of multilayer printed circuit boards?

A45. Difficulty of repair of internal connections.

Q46. What was the earliest form of micromodule?

A46. Cordwood modules. Q47. In what publication are environmental requirements for equipment defined?

A47. Procurement specifications. Q48. In what publication would you find guidelines for performance of military electronic parts?

A48. Military Standards. Q49. Who is responsible for meeting environmental and electrical requirements of a system?

A49. Equipment designers (planners). Q50. What methods are used to prevent unwanted component interaction?

A50. Ground planes, shielding, and component placement.

MICROWAVE ANTENNAS

Q-1. Microwave antennas and low-frequency antennas are similar in what ways?

A-1. Operating principles and electrical characteristics.

Q-2. What term is used to express the efficiency of an antenna?

A-2. Power gain or power ratio. Q-3. What term is used to express the measurement of the degree of mismatch between a line and its load?

A-3. Standing-wave ratio (swr). Q-4. What type of antenna radiates in and receives energy from all directions at once?

A-4. Omnidirectional. Q-5. What is the term that is used to describe narrowness in the radiated beam of an antenna?

A-5. Antenna directivity. Q-6. What characteristic allows the same antenna to both transmit and receive?

A-6. Reciprocity. Q-7. What type of reflector is most often used in directive antennas?

A-7. Parabolic. Q-8. Microwaves can be focused and reflected in the same way as what other type of waves?

A-8. Light waves. Q-9. How many major lobes are radiated by a parabolic reflector?

A-9. One. Q-10. A horizontally truncated paraboloid antenna is used for what purpose?

A-10. Determine elevation. Q-11. The beam from a horizontally positioned cylindrical paraboloid is narrow in what plane?

A-11. Vertical.

Q-12. What is the purpose of a collimating lens?

A-12. Forces the radial segments of a wavefront into parallel paths. Q-13. How does a waveguide-type lens focus spherical wavefront microwave energy? A-13. Some wavefronts are accelerated so that all wavefronts exit the lens at the same time. Q-14. What type of lens decelerates a portion of a spherical wavefront?

A-14. Delay lens.

Q-15. What is a set of antenna elements called?

A-15. Antenna Array. Q-16. What type of antenna has all elements connected to the same energy source?

A-16. Driven Array. Q-17. What determines the beam elevation angle of an antenna that is electronically scanned in elevation?

A-17. Frequency or phase of radiated energy.

Q-18. What is the polarization of the energy radiated by a vertical

NEETS Q&A

slot?

A-18. Horizontal.

MICROWAVE COMPONENTS AND CIRCUITS

Q-1. What happens to the impedance of interelectrode capacitance as frequency increases?

A-1. Impedance decreases. Q-2. What undesirable effect is caused by the inductance of the cathode lead?

A-2. Degenerative feedback. Q-3. How does transit time affect the relationship of the grid voltage and the plate current at high frequencies? A-3. Transit time causes the grid voltage and plate current to be out of phase. Q-4. Moving tube electrodes apart to decrease interelectrode capacitance causes an increase in the effect of what property?

A-4. Transit time. Q-5. The kinetic energy of an electron is directly proportional to what property?

A-5. Velocity. Q-6. What will be the effect upon an electron traveling in the opposite direction to the lines of force in an electrostatic field?

A-6. The electron will be accelerated.

Q-7. How is a beam of electrons velocity-modulated?

A-7. By alternately speeding up or slowing down the electrons. Q-8. What portion of an electron gun causes the electrons to accelerate or decelerate?

A-8. The buncher grids. Q-9. What is the effect upon an electron that enters the buncher gap when the potential across the grids is at 0 volts?

A-9. There is no effect.

Q-10. What determines the placement of the catcher cavity?

A-10. The frequency period of the buncher grid signal.

Q-11. What is the basic principle of operation of a klystron?

A-11. Velocity modulation. Q-12. The electrons in the beam of a klystron are speeded up by a high dc potential applied to what elements?

A-12. The accelerator grid and the buncher grids. Q-13. The two-cavity klystron uses what cavity as an output cavity?

A-13. The catcher cavity. Q-14. A two-cavity klystron without a feedback path will operate as what type of circuit?

A-14. Amplifier. Q-15. What can be added to the basic two-cavity klystron to increase the amount of velocity modulation and the power output?

A-15. Intermediate cavities between the input and output cavities. Q-16. How is the electron beam of a three-cavity klystron accelerated toward the drift tube?

A-16. A large negative pulse is applied to the cathode. Q-17. Which cavity of a three-cavity klystron causes most of the velocity modulation?

A-17. The middle cavity. Q-18. In a multicavity klystron, tuning all the cavities to the same frequency has what effect on the bandwidth of the tube?

A-18. The bandwidth decreases. Q-19. The cavities of a multicavity klystron are tuned to slightly different frequencies in what method of tuning?

A-19. Stagger tuning. Q-20. What element of the reflex klystron replaces the output cavity of a normal klystron?

A-20. The reflector or repeller. Q-21. When the repealer potential is constant, what property of the electron determines how long it will remain in the drift space of the reflex klystron?

A-21. Velocity. Q-22. The constant-speed electrons of an electron bunch in a reflex klystron must remain in the repeller field for what minimum time?

A-22. Three-quarter cycle. Q-23. If the constant-speed electrons in a reflex klystron remain in the repeller field for 1 3/4 cycles, what is the mode of operation?

A-23. Mode 2. Q-24. Debunching of the electron bunches in the higher modes of a reflex klystron has what effect on output power?

A-24. Power is reduced.

Q-25. What limits the tuning range around the center frequency of a reflex klystron in a particular mode of operation?

A-25. The half-power points of the mode.

Q-26. What is the primary use of the twt?

A-26. Voltage amplification. Q-27. The magnet surrounding the body of a twt serves what purpose?

A-27. Used to focus the electrons into a tight beam. Q-28. How are the input and output directional couplers in a twt connected to the helix? A-28. The directional couplers are not physically connected to the helix. Q-29. What relationship must exist between the electron beam and the traveling wave for bunching to occur in the electron beam of a twt? A-29. The traveling wave must have a forward velocity equal to or less than the speed of the electrons in the beam. Q-30. What structure in the twt delays the forward progress of the traveling wave?

A-30. The helix. Q-31. The folded waveguide in a bwo serves the same purpose as what component in a twt?

A-31. Helix.

Q-32. What serves as a grid in a magnetron?

A-32. A magnetic field. Q-33. A cylindrical copper block with resonant cavities around the circumference is used as what component of a magnetron?

A-33. Anode or plate.

Q-34. What controls the output frequency of a magnetron?

A-34. The resonant cavities. Q-35. What element in the magnetron causes the curved path of electron flow?

A-35. The permanent magnet. Q-36. What is the term used to identify the amount of field strength required to cause the electrons to just miss the plate and return to the filament in a circular orbit?

A-36. The critical value of field strength. Q-37. A magnetron will produce oscillations when the electrons follow what type of path?

A-37. Circular. Q-38. What is the primary difference in construction between the basic magnetron and the negativeresistance magnetron?

A-38. The negative-resistance magnetron has a split plate. Q-39. What starts the oscillations in a negative-resistance magnetron?

A-39. The application of the proper magnetic field. Q-40. Why is the negative-resistance magnetron often operated with reduced filament voltage?

A-40. To reduce the effects of filament bombardment. Q-41. What type of electron-resonance anode block does not require strapping?

A-41. Rising-sun block. Q-42. Without strapping, the resonant cavities of a hole-and-slot anode are connected in what manner?

A-42. Series. Q-43. What are the electrons called that give up energy to the ac field in a magnetron?

A-43. Working electrons. Q-44. Why is the pi mode the most commonly used magnetron mode of operation?

A-44. Greater power output. Q-45. What two methods are used to couple energy into and out of magnetrons?

A-45. Loops and slots. Q-46. Magnetron tuning by altering the surface-to-volume ratio of the hole portion of a hole-and-slot cavity is what type of tuning?

A-46. Inductive. Q-47. Capacitive tuning by inserting a ring into the cavity slot of a magnetron is accomplished by what type of tuning mechanism?

A-47. A cookie-cutter tuner. Q-48. Name the procedure used to reduce excessive arcing in a magnetron?

A-48. Baking in. Q-49. What causes the negative-resistance property of tunnel diodes?

A-49. The tunneling action.

Q-50. What determines the frequency of a tunnel-diode

NEETS Q&A

oscillator?

A-50. The tuned circuit or cavity frequency.

Q-51. Why is the tunnel diode loosely coupled to the cavity in a tunnel-diode oscillator?

A-51. To increase the stability. Q-52. What is the purpose of the circulator in a tunnel-diode amplifier?

A-52. Prevent feedback to the tuned input circuit. Q-53. What limits the usefulness of high-gain, tunnel-diode frequency converters?

A-53. Stability problems. Q-54. The varactor is a pn junction that acts as what type of electronic device?

A-54. Variable capacitor. Q-55. The underlying principle of operation of the parametric amplifier is based on what property?

A-55. Reactance. Q-56. What is the most important feature of the parametric amplifier?

A-56. The low-noise characteristic. Q-57. How is amplification achieved in the circuit shown in figure 2-43?

A-57. By varying the amount of capacitance in the circuit.

Q-58. What is the purpose of the pump in a parametric amplifier?

A-58. Supplies the electrical energy required to vary the capacitance. Q-59. The pump signal frequency must be of what value when compared to the input signal of a simple parametric amplifier?

A-59. Exactly double the input frequency. Q-60. What is the primary difference between the pump signal of a simple parametric amplifier and the pump signal of a nondegenerative parametric amplifier? A-60. The pump signal of a nondegenerative parametric amplifier is higher than twice the input signal. Q-61. In a nondegenerative parametric amplifier the difference between the input frequency and the pump frequency is called what?

A-61. Idler- or lower-sideband frequency. Q-62. What is the output frequency of an upper-sideband parametric-frequency converter?

A-62. The sum of the input frequency and the pump frequency. Q-63. What is the primary advantage of bulk-effect devices over normal pn-junction semiconductors?

A-63. Larger microwave power outputs. Q-64. What happens to the electrons of a gallium-arsenide semiconductor when they move from the normal low-energy conduction band to the high-energy conduction band?

A-64. The electrons become immobile. Q-65. The point on the current curve of a gallium-arsenide semiconductor at which it begins to exhibit negative resistance is called what?

A-65. Threshold. Q-66. The domain in a gallium-arsenide semiconductor has what type of electrical field when compared to the other regions across the body of a semiconductor?

A-66. A field of much greater intensity. Q-67. What characteristic of a gunn oscillator is inversely proportional to the transit time of the domain across the semiconductor?

A-67. The frequency. Q-68. What is the junction arrangement of the original avalanche transit-time diode?

A-68. Pnin. Q-69. What causes dc bias energy to be absorbed by avalanche electrons and given up to the microwave field applied to an avalanche transit-time diode?

A-69. The negative-resistance property. Q-70. During the manufacture of a point-contact diode, what is the purpose of passing a relatively large current from the catwhisker to the silicon crystal?

A-70. To form a small region of p-type material. Q-71. What is the capacitive reactance across a point-contact diode as compared to a normal junction diode?

A-71. Lower. Q-72. What are the most important advantages of the Schottky barrier diode?

A-72. Lower forward resistance and low noise. Q-73. At frequencies above 100 megahertz, the intrinsic (i) region causes a pin diode to act as what?

A-73. Variable resistance.

Q-74. The pin diode is primarily used for what purpose?

A-74. A switching device.

MINIATURE AND MICROMINIATURE REPAIR PROCEDURES

Q1. What material is applied to electronic assemblies to prevent damage from corrosion, moisture, and stress?

A1. Conformal coating.

Q2. What three methods are used to remove protective material?

A2. Chemical, mechanical, and thermal.

Q3. What chemicals are used to remove protective material?

A3. Solvents or xylene and trichloroethane. Q4. Abrasion, cutting, and peeling are examples of what type of protective material removal?

A4. Mechanical. Q5. Why should the coating material be replaced once the required repair has been completed?

A5. To ensure protective characteristics are maintained. Q6. What term is used to identify the procedure of connecting one side of a circuit board with the other?

A6. Interfacial connections.

Q7. Name two types of through-hole termination.

A7. Clinched lead, straight-through, and offset pad. Q8. Turret, bifurcated, and hook terminals are used for what type of termination?

A8. Above-the-board termination. Q9. When a lead is soldered to a pad without passing through the board, it is known as what type of termination?

A9. On-the-board termination.

Q10. When does most printed circuit board damage occur?

A10. During disassembly or repair. Q11. What procedure involves the use of finely braided copper wire to remove solder?

A11. Wicking.

Q12. What is the most effective method of solder removal?

A12. Continuous vacuum. Q13. When, if at all, should the heat-and-shake or the heat-and-pull methods of solder removal be used?

A13. These methods should not be used. Q14. To what standards should a technician restore electronic assemblies?

A14. Manufacturer's standards.

Q15. How is oxide removed from pads and component leads?

A15. A fine abrasive. Q16. Leads are formed approximately how many degrees from their major axis?

A16. 90 degrees. Q17. When you replace components, identification marks must meet what requirements?

A17. They should be readable from a single point. Q18. In what direction are component leads clinched on single- and double-sided boards?

A18. In the direction of the run.

Q19. What is solderability? A19. The ease with which molten solder wets the surfaces of the metals to be joined. Q20. What is the most common source of heat in electronic soldering?

A20. Conductive-type soldering iron.

Q21. What determines the shape and size of a soldering iron tip?

A21. The type of work to be done. Q22. What term describes a device used to conduct heat away from a component?

A22. A thermal shunt.

Q23. What is the appearance of a properly soldered joint?

A23. Bright and shiny with no cracks or pits. Q24. When removing the component, under what circumstances may component leads be clipped? A24. If the component is known to be defective or if the board may be damaged by normal desoldering.

Q25. How are imbedded TOs removed once the leads are free?

A25. By pushing it gently out of the board.

Q26. How is a flat pack removed from a pcb?

A26. Heat each lead and lift with tweezers. Q27. How do you prevent excessive heat buildup on an area of a board when soldering multilead components?

NEETS Q&A

A27. Use a skipping pattern.

Q28. What are the two final steps of any repair?

A28. Inspect and test.

Q29. List three causes of damage to printed circuit boards. A29. Operational failures, repairs by untrained personnel, repair using improper tools, mishandling, improper shipping, packaging, and storage. Q30. What is the preferred method of repairing cracked runs on boards?

A30. Clinched staple. Q31. Damaged or missing termination pads are replaced using what procedure? A31. Epoxy a replacement pad to the board, set an eyelet, and solder it.

Q32. How is board damage caused by technicians? A32. Repairs by untrained personnel and technicians using improper tools. Q33. What combination of materials is used to patch or build up damaged areas of boards?

A33. Epoxy and fiberglass powder. Q34. List two causes of damage to ESD-sensitive electronic components.

A34. Esd, improper stowage, and improper handling.

Q35. What is the purpose of the wrist ground strap?

A35. To discharge any static charge built up in the body.

Q36. What is the cause of most accidents?

A36. Deviation from prescribed safe operating procedures.

MINIATURE/MICROMINIATURE (2M) REPAIR PROGRAM AND HIGH-RELIABILITY SOLDERING

Q1. Training requirements for (2M) repair personnel were developed under guidelines established by what organization?

A1. Chief of Naval Operations (CNO). Q2. What agencies provide training, tools, equipment, and certification of the 2M system? A2. Naval Sea Systems Command (NAVSEASYSCOM) and Naval Air Systems Command (NAVAIRSYSCOM). Q3. To perform microminiature component repair, a 2M technician must be currently certified in what area?

A3. Microminiature component repair. Q4. Multilayer printed circuit board repair is the responsibility of what 2M repair technician?

A4. Microminiature repair technician.

Q5. What are the three levels of maintenance?

A5. Depot, Intermediate, and Organizational. Q6. Maintenance performed by the user activity is what maintenance level?

A6. Organizational. Q7. List the three groups of test equipment used for fault isolation in 2M repair. A7. On-line, off-line, and General Purpose Electronic Test Equipment (GPETE). Q8. What test equipment continuously monitors electronic systems?

A8. On-line. Q9. NELAT and VAST are examples of what type of test equipment?

A9. Off-line. Q10. Stereoscopic-zoom microscopes and precision drill presses are normally associated with what type of repair station?

A10. Microminiature repair station. Q11. Solder used in electronic repair is normally an alloy of what two elements?

A11. Tin and lead. Q12. In soldering, what alloy changes directly from a solid state to a liquid state?

A12. Eutectic. Q13. Flux aids in soldering by removing what from surfaces to be soldered?

A13. Oxides. Q14. What type(s) of flux should never be used on electronic equipment?

A14. Chloride or (acid) and organic.

MISCELLANEOUS MEASUREMENTS

Q-1. What is the logarithmic ratio between the input and output

of a given circuit called?

A-1. Bel. Q-2. What term is used to represent power levels above or below a 1-milliwatt reference?

A-2. dBm.

Q-3. What milliwatt value is equal to +6 dBm?

A-3. 4 mW. Q-4. What name is given to a resistor used to replace the normal load in a circuit?

A-4. Dummy load or dummy antenna.

Q-5. What are the two types of bolometers?

A-5. Barretter and thermistor. Q-6. As the dissipated power increases, what effect does this have on the resistance of a thermistor?

A-6. It increases. Q-7. In a heterodyne-type frequency meter, what is the difference between the oscillator frequency and the unknown frequency?

A-7. Beat frequency. Q-8. What equipment uses a calibrated resonant circuit to measure frequency?

A-8. Wavemeter.

Q-9. Name two instruments used to analyze waveforms.

A-9. Oscilloscope and spectrum analyzer. Q-10. What device sweeps a band of frequencies to determine frequencies and amplitudes of each frequency component?

A-10. Spectrum analyzer. Q-11. What is the typical back-to-forward resistance ratio of a good-quality diode?

A-11. 10-to-1 ratio.

Q-12. As a transistor ages, what happens to the leakage current?

A-12. It tends to increase.

NUMBER SYSTEMS

Q1. What term describes a single object?

A1. Unit Q2. A symbol that represents one or more objects is called a _________.

A2. Number Q3. The symbols 0, 1, 2, and 3 through 9 are what type of numerals?

A3. Arabic Q4. What does the base, or radix, of a number system tell you about the system?

A4. The number of symbols used in the system

Q5. How would you write one hundred seventy-three base 10?

A5. 17310

Q6. What power of 10 is equal to 1,000? 100? 10? 1?

A6. 103, 102, 101, 100, Q7. The decimal point of the base 10 number system is also known as the _________.

A7. Radix point

Q8. What is the MSD and LSD of the following numbers

(a) 420.

(b) 1045.06

(c) 0.0024

(d) 247.0001

(a) MSD - 4, LSD - 0

(b) MSD - 1, LSD - 6

(c) MSD - 2, LSD - 4

(d) MSD - 2, LSD - 1

OPERATIONAL CONCEPTS

Q-1. How are computers classified? A-1. Technology (mechanical, electromechanical, electronic), purpose (special or general), type of data they handle (analog or digital), cost, physical size (handheld to room size).

Q-2. Mechanical computers are considered to be of what type?

A-2. Analog. Q-3. The Navy uses analog computers primarily for what purpose?

A-3. Gun fire control. Q-4. How do electromechanical computers differ from the mechanical computers?

NEETS Q&A

A-4. Electromechanical computers use electrical components to perform some of the calculations. Q-5. In electronic computers, vacuum tubes were replaced by transistors and transistors have been replaced by what device?

A-5. Integrated circuits. Q-6. A computer that is designed to perform a specific operation and usually satisfies the needs of a particular type of problem, is said to be what type of computer?

A-6. Special-purpose. Q-7. Rather than using a stored program, a special-purpose computer's applicability to a particular problem is a function of what?

A-7. Its design.

Q-8. What is a drawback to the special-purpose computer?

A-8. Lack of versatility.

Q-9. A general-purpose computer is designed for what purpose?

A-9. To perform a wide variety of functions and operations. Q-10. How is a general-purpose computer able to perform different operations?

A-10. By storing different programs in its internal storage. Q-11. In a general-purpose computer, the ability to perform a wide variety of operations is achieved at the expense of what capabilities?

A-11. Speed and efficiency.

Q-12. All analog computers are what type of computers?

A-12. Special-purpose.

Q-13. What are analog computers designed to measure?

A-13. Continuous electrical or physical conditions.

Q-14. Early analog computers were what type of devices?

A-14. Mechanical or electromechanical. Q-15. What are computers called that combine the functions of both analog and digital computers?

A-15. Hybrid computers.

Q-16. Digital computers are generally used for what purposes?

A-16. Business and scientific data processing. Q-17. What is the fundamental difference between analog and digital computers? A-17. Digital computers deal with discrete quantities, while analog computers deal with continuous physical variables.

Q-18. How is the accuracy of an analog computer restricted? A-18. By the accuracy with which physical quantities can be sensed and displayed. Q-19. A constant represented by a voltage can be read to what decimal place?

A-19. Third. Q-20. The accuracy of a digital computer is governed by what factor?

A-20. The number of significant figures carried in the computations. Q-21. In a digital computer, what does the number of decimal places in the constant depend on?

A-21. Design of the computer processing unit. Q-22. You will most likely be working with what type of computer?

A-22. General-purpose digital computer. Q-23. Technological advancement is measured by what, in the electronic computer world?

A-23. Generations.

Q-24. What does each generation of computer systems indicate?

A-24. Significant change in computer design. Q-25. What were computers of the first generation characterized by?

A-25. The vacuum tube. Q-26. How did vacuum tubes cause a problem for first generation computers? A-26. They were unreliable, required a lot of power to run, and produced so much heat that air conditioning was needed to protect computer parts. Q-27. In first generation computers, internal processing functions were measured by what division of time?

A-27. Thousandths of a second (millisecond). Q-28. The software (computer program) used on first generation computers was what type?

A-28. Unsophisticated and machine oriented. Q-29. How were processing speed and reliability increased in second generation computers?

A-29. By the use of small, long lasting transistors. Q-30. In second generation computers, how was the storage capacity greatly increased?

A-30. With the introduction of magnetic disk storage and the use of

core for main storage.

Q-31. With improvements in software, what kind of computer languages could be used on second generation computers?

A-31. Symbolic machine languages or assembly languages.

Q-32. What do the smaller circuits in third generation computers allow for?

A-32. Faster internal processing speeds. Q-33. On third generation computers, what results are gained by faster internal processing speeds?

A-33. Faster execution of instructions. Q-34. The data cell had a storage capacity of how many characters?

A-34. Over 100 million. Q-35. What type of applications were most third generation computer systems designed to accomplish?

A-35. Both scientific and business data processing applications. Q-36. What type of computers are small and inexpensive yet provide a lot of computing power?

A-36. Microcomputers and minicomputers.

Q-37. What does the acronym ROM stand for?

A-37. Read-only memory. Q-38. What will be one of the future challenges involving computer power? A-38. How to properly and effectively use the computing power available. Q-39. What term is used for programs such as assemblers, compilers, and operating systems?

A-39. Software.

Q-40. What is one of the more widespread uses of the computer?

A-40. Word processing. Q-41. What is the great advantage of computers over typewriters?

A-41. Correcting errors.

Q-42. How are word processing programs used by the Navy? A-42. For manuscript writing, memorandum writing, identification-card application filing, and recordkeeping. Q-43. How many systems dealing with accounting applications have been widely accepted?

A-43. Six.

Q-44. What does the acronym S-N-A-P stand for?

A-44. Shipboard Non-tactical ADP Program.

Q-45. For what purposes is the SNAP II system designed? A-45. To support shipboard and intermediate level maintenance, supply, financial, and administrative functions.

Q-46. What does user friendly mean in computer terms?

A-46. Operating instructions are written in everyday English.

Q-47. What does a password prevent?

A-47. Unauthorized entry into the main computer's program. Q-48. In the SNAP II system, how are the different levels of entry defined?

A-48. Dependent on a work center's need. Q-49. The work center supervisor can update what items from a user terminal?

A-49. COSAL, APL, EIC, SHIP'S FORCE WORK LIST, and CSMP. Q-50. At present what type of classified use is allowed for SNAP II?

A-50. Unclassified. Q-51. What is a central set of programs called that manages the execution of other programs and performs common functions like read, write, and print?

A-51. Operating system. Q-52. What is the function of a built-in program called a bootstrap loader? A-52. To load an external operating system into the computer's internal memory. Q-53. When you see the error message NO SYSTEM, what does it mean? A-53. The computer is reading a properly inserted floppy disk, but it does not have an operating system on it. Q-54. When an operating system prompt (A>) is displayed on the screen, what do you enter from the keyboard to load an application program?

A-54. The program name.

Q-55. If disks are stored horizontally, how many can be stacked?

A-55. No more than ten. Q-56. What can exposure to a magnetic field do to the data on a disk?

A-56. Destroy some or all of it.

NEETS Q&A

Q-57. What is the temperature range within which a disk will operate?

A-57. 10 to 50 degrees Celsius or 50 to 120 degrees Fahrenheit. Q-58. What is the most common method to ensure that any stored data lost can be recovered?

A-58. Backup files. Q-59. The most common method of creating a backup for a microcomputer is what?

A-59. Use a floppy disk and the diskcopy procedure. Q-60. Other than disk, what is another media used for backup files?

A-60. Magnetic tape.

OPTICAL DETECTORS AND FIBER OPTIC RECEIVERS

Q1. What is a fiber optic receiver? A1. An electro-optic device that accepts optical signals from an optical fiber and converts them into electrical signals. Q2. Which part of the receiver amplifies the electrical signal to a level suitable for further signal processing?

A2. Amplifier. Q3. Which performance parameter is the minimum amount of optical power required to achieve a specific bit-error rate (BER) in digital systems or a given signal-to-noise ratio (SNR) in analog systems?

A3. Receiver sensitivity.

Q4. Define receiver dynamic range. A4. The range of optical power levels over which the receiver operates within the specified values. It

Q5. Describe the operation of an optical detector. A5. It is a transducer that converts an optical signal into an electrical signal. It does this by generating an electrical current proportional to the intensity of incident optical radiation. Q6. For efficient operation, should a detector have a high or low responsivity at the operating wavelength?

A6. High. Q7. List the two principal optical detectors used in fiber optic systems. A7. The semiconductor positive-intrinsic-negative (PIN) photodiode and avalanche photodiode (APD). Q8. What are the four most common materials used in semiconductor detector fabrication?

A8. Silicon, gallium arsenide, germanium, and indium phosphide.

Q9. What is a photocurrent? A9. The current produced when photons are incident on the detector active area.

Q10. Define responsivity. A10. The ratio of the optical detector's output photocurrent in amperes to the incident optical power in watts.

Q11. How are PIN photodiodes usually biased?

A11. Reverse-biased.

Q12. What is the dark current? A12. The leakage current that continues to flow through a photodetector when there is no incident light. Q13. Will dark current increase or decrease as the temperature of the photodiode increases?

A13. Increase. Q14. Should the capacitance of the photodetector be kept small or large to prevent the RC time constant from limiting the response time?

A14. Small. Q15. Trade-offs between competing effects are necessary for high speed response. Which competing effect (fast transit time, low capacitance, or high quantum efficiency) requires a thin active area?

A15. Fast transit time. Q16. Why is detector saturation not generally a problem in fiber optic communications systems? A16. Because fiber optic communications systems operate at low optical power levels.

Q17. Describe avalanche multiplication. A17. The electrons initially generated by the incident photons accelerate as they move through the APD active region. As these electrons collide with electrons in the semiconductor material, they cause a fraction of them to become part of the photocurrent.

Q18. How can the gain of an APD be increased?

A18. By increasing the reverse-bias voltage. Q19. Which amplifier stage (the preamplifier or the postamplifier) is a dominant contributor of noise and significantly influences the sensitivity of the receiver?

A19. The preamplifier.

Q20. List the key operational parameters used to define receiver performance.

A20. Receiver sensitivity, bandwidth, and dynamic range.

Q21. List the main types of receiver noise.

A21. Thermal noise, dark current noise, and quantum noise. Q22. What is the main factor that determines receiver sensitivity?

A22. Noise. Q23. For a reduction in thermal noise, should the value of the detector's load resistor be increased or decreased?

A23. Increased. Q24. What are two types of noise that manifest themselves as shot noise?

A24. Dark current and quantum noises. Q25. What are the two basic types of preamplifiers used in fiber optic receivers?

A25. The high-impedance amplifier and the transimpedance amplifier. Q26. Which preamplifier design (high-impedance or transimpedance) provides improvements in bandwidth and greater dynamic range with some degradation in sensitivity from an increase in noise?

A26. Transimpedance.

Q27. For what types of applications are APDs generally used? A27. For high-data-rate applications and for low- or moderate-data-rate applications where receivers with extremely low sensitivities are required. Q28. Why is a low-pass filter generally part of a digital fiber optic receiver? A28. To smooth the amplified signal to remove some of the high frequency noise before the signal is further processed.

OPTICAL FIBERS AND CABLES

Q1. Describe the term "refractive index profile." A1. Refractive index profile describes the value of refractive index as a function of radial distance at any fiber diameter. Q2. The refractive index of a fiber core is uniform and undergoes an abrupt change at the corecladding boundary. Is this fiber a step-index or graded-index fiber?

A2. Step-index. Q3. Multimode optical fibers can have a step-index or graded-index refractive index profile. Which fiber, multimode step-index or multimode graded-index fiber, usually performs better?

A3. Multimode graded-index fiber. Q4. List the standard core sizes for multimode step-index, multimode graded-index, and single mode fibers. A4. Multimode step-index fibers: 50µm and 100µm. Multimode graded-index fibers: 50µm, 62.5µm, 85µm, and 100µm. Single mode fibers: between 8µm and 10µm. Q5. Multimode step-index fibers have a core and cladding of constant refractive index n1 and n2, respectively. Which refractive index, the core or cladding, is lower?

A5. Cladding. Q6. In multimode step-index fibers, the majority of light propagates in the fiber core for what reason? A6. Most modes in multimode step-index fibers propagate far from cutoff. Q7. Multimode step-index fibers have relatively large core diameters and large numerical apertures. These provide what benefit? A7. Make it easier to couple light from a light-emitting diode (LED) into the fiber. Q8. The profile parameter (α) determines the shape of the multimode graded-index core's refractive index profile. As the value of the aincreases, how does the core's profile change?

A8. From a triangular shape to step. Q9. Light propagates in multimode graded-index fibers according to refraction and total internal reflection. When does total internal reflection occur? A9. When the angle of incidence becomes larger than the critical angle of incidence. Q10. What four fiber properties determine the number of modes propagating in a multimode gradedindex fiber? A10. Numerical aperture (NA), relative refractive index difference ( D), profile parameter (α), and normalized frequency (V). Q11. Light travels faster in a material with a lower refractive index. Therefore, light rays that travel a longer distance in a lower refractive index travel at a greater average velocity. What effect does this have on multimode graded-index fiber modal dispersion and bandwidth? A11. Decreases the time difference between light rays, which reduces modal dispersion and increases fiber bandwidth. Q12. What multimode graded-index fiber offers the best overall performance for most applications?

A12. 62.5/125 mm multimode graded-index fiber.

NEETS Q&A

Q13. What are the most distinguishing characteristics of a multimode graded-index fiber? A13. Source-to-fiber coupling efficiency and insensitivity to microbending and macrobending losses. Q14. How are source-to-fiber coupling and microbending and macrobending losses affected by changes in core diameter and D? A14. Coupling efficiency increases with both core diameter and D, while bending losses increase directly with core diameter and inversely with D. Q15. While coupled power and bending loss favor a high D, which Dvalue, smaller or larger, improves fiber bandwidth?

A15. Smaller. Q16. What are the two basic types of single mode step-index fibers?

A16. Matched-clad and depressed-clad. Q17. Which fiber cladding, matched or depressed, consists of two regions?

A17. Depressed. Q18. In single mode operation, the value of the normalized frequency (V) should remain near the 2.405 level. If the value of V is less than 1, do single mode fibers carry a majority of the power in the core or cladding material?

A18. Cladding material. Q19. What happens to the fundamental mode as the operating wavelength becomes longer than the single mode cutoff wavelength?

A19. The fundamental mode becomes increasingly lossy. Q20. Give two reasons why the value of the normalized frequency (V) is varied in single mode stepindex fibers? A20. To increase performance and reduce losses caused by bending and splicing.

Q21. Give two reasons why optical fiber manufacturers depart from the traditional circular core and cladding, low-loss glass fiber design?

A21. To increase performance and reduce cost. Q22. What five characteristics do applications using plastic clad silica (PCS) and all-plastic fibers typically have? A22. High NA, low bandwidth, tight bend radius, short length, and low cost. Q23. List the types of materials used in fabricating low-loss, long wavelength optical fibers. A23. Heavy-metal fluorides, chalcogenide glasses, and crystalline materials. Q24. What are the two methods used by fiber manufacturers to fabricate multimode and single mode glass fibers?

A24. Vapor phase oxidation and direct-melt process. Q25. Which method, vapor phase oxidation or direct-melt process, transforms deposited material into a solid glass preform by heating the porous material without melting?

A25. Vapor phase oxidation. Q26. List three benefits that properly cabled optical fibers provide. A26. a. Protect optical fibers from damage or breakage during installation and over the fiber's lifetime. b. Provide stable fiber transmission characteristics compared with uncabled fibers. c. Maintain the physical integrity of the optical fiber. Q27. In addition to a primary coating, manufacturers add a layer of buffer material for what reasons? A27. To provide additional mechanical protection and preserve the fiber's inherent strength. Q28. List the three techniques used by manufacturers to buffer optical fibers.

A28. Tight-buffered, loose-tube, and gel-filled loose-tube.

Q29. List seven properties cable jackets should have. A29. Low smoke generation, low toxicity, low halogen content, flame retardance, fluid resistance, high abrasion resistance, and stable performance over temperature. Q30. List the three types of cable designs being considered by the Navy. A30. Optical fiber cable component (OFCC), stranded, and ribbon cables designs.

Q31. Describe an optical fiber cable component (OFCC). A31. OFCCs are tight-buffer fiber surrounded by arimid yarn and a low-halogen outer jacket. Q32. Two layers of arimid yarn strength members encase the OFCC units. Why are these strength members stranded in opposing directions?

A32. To minimize microbending of the fibers. Q33. Why do cable manufacturers introduce a controlled twist to the stacked ribbons during the cabling process?

A33. To minimize fiber stress when the cable is bent.

Q34. OFCC, stranded, and ribbon cables have different fiber

capacities. What is the approximate number of fibers that each cable can accommodate in a 0.5-inch cable?

A34. OFCC (12 fibers), stranded (48 fibers), ribbon (204 fibers). Q35. Which fiber optic cable (OFCC, stranded, or ribbon) has the worst bend performance?

A35. Ribbon.

OPTICAL SOURCES AND FIBER OPTIC TRANSMITTERS

Q1. What are the three parts of a fiber optic transmitter?

A1. Interface circuit, source drive circuit, and an optical source. Q2. Which part of a fiber optic transmitter converts the processed electrical signal to an optical signal?

A2. The optical source. Q3. LEDs operating at 850 nm provide sufficient optical power for short-distance, low-bandwidth multimode systems. List three conditions that prevent the use of LEDs in longer distance, higher bandwidth multimode systems. A3. Multimode fiber dispersion, the relatively high fiber attenuation, and the LED's relatively low optical output power. Q4. Why can multimode graded-index fiber 1300-nm systems using LEDs operate over longer distances and at higher bandwidths than 850-nm systems? A4. Longer distances and higher bandwidths are possible because fiber material losses and dispersion are significantly reduced at the 1300-nm region. Q5. Semiconductor LEDs emit incoherent light. Define incoherent light.

A5. Light waves that lack a fixed-phase relationship. Q6. Which semiconductor sources (LD or LED) emit more focused light and are capable of launching sufficient optical power into both single mode and multimode fibers?

A6. LDs. Q7. The amount of optical power coupled into an optical fiber depends on what four factors? A7. (1) The angles over which the light is emitted. (2) The size of the source's light-emitting area relative to the fiber core size. (3) The alignment of the source and fiber. (4) The coupling characteristics of the fiber (such as the NA and the refractive index profile). Q8. What are the two most common semiconductor materials used in electronic and electro-optic devices?

A8. Silicon and gallium arsenide.

Q9. What is a laser? A9. A laser is a device that produces optical radiation using stimulated emission rather than spontaneous emission.

Q10. .Describe stimulated emission. A10. A photon initially produced by spontaneous emission in the active region interacts with the laser material to produce additional photons.

Q11. What are the three basic LED types? A11. Surface-emitting LEDs (SLEDs), edge-emitting LEDs (ELEDs), and superluminescent diodes (SLDs). Q12. Which types of LEDs are the preferred optical sources for short-distance, low-data-rate fiber optic systems?

A12. SLEDs and ELEDs.

Q13. What are facets? A13. Cut or polished surfaces at each end of the narrow active region of an ELED. Q14. What is lowest current at which stimulated emission exceeds spontaneous emission in a semiconductor laser called?

A14. Threshold current.

Q15. Describe the output of a laser diode. A15. The LD's output has a narrow spectral width and small output beam angle. Q16. Which type of optical source usually lacks reflective facets and in some cases are designed to suppress reflections back into the active region?

A16. LED. Q17. Which type of optical source tends to operate at higher drive currents to produce light?

A17. Laser. Q18. Are the effects of temperature changes on LDs more or less significant than for LEDs?

A18. More. Q19. Specify the mechanism that SLDs lack that is required by laser diodes to achieve lasing.

A19. SLDs have no built-in optical feedback mechanism. Q20. How does the source drive circuit intensity modulate the source?

A20. By varying the current through the source.

Q21. What is a prebias?

A21. A current applied in the laser off state just less than the

NEETS Q&A

threshold current.

Q22. Is the drive circuitry generally more complex for an LED or a laser diode? Why? A22. For a laser diode. The laser diode transmitter generally contains output power control circuitry and may contain a TE cooler and some circuitry associated with the TE cooler. Q23. What are the two types of output interfaces for fiber optic transmitters?

A23. Optical connectors and optical fiber pigtails.

Q24. List five common fiber optic transmitter packages. A24. TO can, DIP, butterfly lead microcircuits, circuit cards, and stand-alone optical fiber converters. Q25. What type of source is typically used in low-data-rate digital applications?

A25. LED. Q26. Why would a laser diode be used in a low-data-rate digital application?

A26. When extremely high transmitter output powers are required. Q27. What type of source is generally used in high-data-rate digital applications?

A27. Laser diode. Q28. Why are LEDs preferred over laser diodes for low- and moderate-frequency analog applications?

A28. LEDs require less complex circuitry than lasers.

OPTICAL SPLICES, CONNECTORS, AND COUPLERS

Q1. Which fiber optic component (splice, connector, or coupler) makes a permanent connection in a distributed system?

A1. Splice.

Q2. What are the main causes of coupling loss?

A2. Poor fiber end preparation and poor fiber alignment.

Q3. Define the loss in optical power through a connection.

A3.Po

Pi

1010logloss =

Q4. Fiber-to-fiber coupling loss is affected by intrinsic and extrinsic coupling losses. Can intrinsic coupling losses be limited by limiting fiber mismatches?

A4. Yes. Q5. In fiber-to-fiber connections, Fresnel reflection is one source of coupling losses. Light is reflected back into the source fiber and is lost. What causes Fresnel reflection? A5. A step change in refractive index that occurs at fiber joints, caused by fiber separation. Q6. Reduction of Fresnel reflection is possible by reducing the step change in the refractive index at the fiber interface. What material reduces the step change in refractive index at a fiber interface?

A6. Index matching gel.

Q7. List the three basic errors that occur during fiber alignment. A7. Fiber separation (longitudinal misalignment), lateral misalignment, and angular misalignment. Q8. When the axes of two connected fibers are no longer in parallel, the two connected fibers are in what kind of misalignment?

A8. Angular misalignment. Q9. How does index matching gel affect the amount of coupling loss caused by (a) fiber separation, (b) lateral misalignment, and (c) angular misalignment? A9. (a) Reduces coupling loss, (b) does not change coupling loss, and (c) increases coupling loss. Q10. Which are more sensitive to alignment errors, single mode or multimode fibers?

A10. Single mode. Q11. Quality fiber-end preparation is essential for proper system operation. What properties must an optical fiber-end face have to ensure proper fiber connection?

A11. Be flat, smooth, and perpendicular to the fiber axis. Q12. What is the basic fiber cleaving technique for preparing optical fibers for coupling?

A12. Score-and-break. Q13. Using a standard microscope to inspect a fiber-end face, you observe that all parts of the fiberend face are in focus at the same time. Is the fiber-end face flat, concave, or convex?

A13. Flat.

Q14. List six types of fiber mismatches. A14. Core diameter mismatch, cladding diameter mismatch, core ellipticity, core and cladding concentricity differences, NA mismatch, and refractive index profile differences. Q15. Does coupling loss from refractive index profile difference result when the receiving fiber has a larger profile parameter (α)

than the transmitting fiber?

A15. No.

Q16. Define a fiber optic splice. A16. A permanent fiber joint whose purpose is to establish an optical connection between two individual optical fibers. Q17. Fiber splicing is divided into two broad categories that describe the techniques used for fiber splicing. What are they?

A17. Mechanical and fusion splicing.

Q18. Describe a transparent adhesive. A18. An epoxy resin that seals mechanical splices and provides index matching between the connected fibers. Q19. The Navy recommends using the rotary splice for what two reasons? A19. It is a low-loss mechanical splice that provides stable environmental and mechanical performance in the Navy environment, and it requires only a small amount of training. Q20. What fiber property directly affects splice loss in fusion splicing?

A20. The angles and quality of the two fiber-end faces. Q21. List two reasons why fusion splicing is one of the most popular splicing techniques in commercial applications. A21. The small size of the fusion splice and the development of automated fusion-splicing machines. Q22. What is a short discharge of electric current that prepares the fiber ends for fusion called?

A22. Prefusion. Q23. Do small core distortions formed by arc fusion's self-alignment mechanism have more of an affect on light propagating through multimode or single mode fibers?

A23. Single mode fibers. Q24. What connection properties result in fiber optic connector coupling loss? A24. Poor fiber alignment and end preparation, fiber mismatches, and Fresnel reflection. Q25. Which is the more critical parameter in maintaining total insertion loss below the required level, fiber alignment or fiber mismatch?

A25. Fiber alignment. Q26. Fiber optic connectors can reduce system performance by increasing what two types of noise?

A26. Modal and reflection. Q27. Which type of fiber optic connector (butt-jointed or expanded beam) brings the prepared ends of two optical fibers into close contact?

A27. Butt-jointed connectors. Q28. Is coupling loss from fiber separation and lateral misalignment more critical in expanded-beam or butt-jointed connectors?

A28. Butt-jointed connectors. Q29. Is coupling loss from angular misalignment more critical in expanded beam or butt-jointed connectors?

A29. Expanded beam connectors. Q30. The Navy classifies fiber optic connectors in what two ways?

A30. Light-duty and heavy-duty connectors. Q31. What is the difference between passive and active fiber optic couplers? A31. Passive couplers redistribute optical signals without optical-to-electrical conversion. Q32. Which type of optical splitter (Y-coupler or T-coupler) splits only a small amount of power from the input fiber to one of the output fibers?

A32. T-coupler.

Q33. Describe a directional coupler. A33. A fiber optic coupler that prevents the transfer of power between input fibers.

OSCILLATORS

Q-1. What are the two classifications of wave generators according to their output waveshapes?

A-1. Sinusoidal and nonsinusoidal. Q-2. What are the three networks used for frequency-determining devices?

A-2. RC, LC, and crystal.

Q-3. What is another name for nonsinusoidal oscillators?

A-3. Relaxation oscillators. Q-4. What is a nonrotating device that produces alternating current?

A-4. Oscillator. Q-5. What are the three requirements necessary for oscillations to exist in a circuit?

NEETS Q&A

A-5. Amplification, regenerative feedback, and frequency-determining device.

Q-6. What type of feedback aids an input signal?

A-6. Regenerative or positive.

Q-7. What are the two methods used for feedback coupling?

A-7. Inductive and capacitive.

Q-8. Which oscillator uses a tickler coil for feedback?

A-8. Armstrong.

Q-9. Which oscillator uses a tapped inductor for feedback?

A-9. Hartley.

Q-10. Which oscillator uses tapped capacitors for feedback?

A-10. Colpitts. Q-11. What are the three basic configurations of transistor oscillators? A-11. Common collector (CC), common emitter (CE), and common base (CB). Q-12. What is the main difference between the Armstrong oscillator and the Hartley oscillator? A-12. Feedback coil. Armstrong uses a separate coil. Hartley uses a tapped coil. Q-13. What is the difference between the series-fed and the shunt-fed Hartley oscillator? A-13. In the series-fed Hartley oscillator, dc flows through the tank circuit.

Q-14. What is the identifying feature of a Colpitts oscillator?

A-14. Split capacitors. Q-15. Which components provide the regenerative feedback signal in the phase-shift oscillator?

A-15. Resistor-capacitor networks. Q-16. Why is a high-gain transistor used in the phase-shift oscillator?

A-16. Because of the losses encountered in the RC networks. Q-17. Which RC network provides better frequency stability, three-section or four-section?

A-17. Four-section. Q-18. What is the impedance of a crystal at its resonant frequency when it is used in the parallel mode?

A-18. Maximum. Q-19. What is the impedance of a crystal at its resonant frequency when it is used in the series mode?

A-19. Minimum. Q-20. Oscillators that are turned on and off at a specific time are known as what type of oscillators?

A-20. Pulsed oscillators. Q-21. What is the polarity of the first alternation of the tank circuit in an emitter-loaded npn pulsed oscillator?

A-21. Negative. Q-22. What is the frequency that is twice the fundamental frequency?

A-22. Second harmonic.

Q-23. What is the purpose of the buffer amplifier?

A-23. Reduce interaction between oscillator and load.

POWER SUPPLIES

Q1. What are the four basic sections to a power supply?

A1. Transformer, rectifier, filter, regulator.

Q2. What is the purpose of the regulator?

A2. To maintain a constant voltage to the load.

Q3. What are the purposes of the transformer in a power supply? A3. It couples the power supply to the ac line voltage, isolates the ac line voltage from the load, and steps this voltage up or down to the desired level. Q4. For what are the low voltage windings in a transformer used?

A4. Filament voltage to the electron tubes.

Q5. For what is the center tap on a transformer used?

A5. Provides capability of developing two high-voltage outputs. Q6. Does a rectifier tube conduct on the positive or negative alternation of the input signal?

A6. Positive. Q7. What term is used to describe the period when the diode is not conducting?

A7. Cutoff. Q8. Current that flows in pulses in the same direction is called _____.

A8. Pulsating dc.

Q9. For a diode to act as a rectifier, should it be connected in series or parallel with the load?

A9. Series. Q10. What is the Ripple frequency of a half-wave rectifier if the input frequency is 60 Hz?

A10. 60 hertz. Q11. What is the equation for determining average voltage in a half-wave rectifier?

A11. Eavg = 0.318 × Emax. Q12. What is the ripple frequency of a full-wave rectifier with an input frequency of 60 Hz?

A12. 120 hertz. Q13. What is the average voltage (Eavg) output of a full-wave rectifier that has an output of 100 volts peak?

A13. 63.6 volts. Q14. What is the main disadvantage of the conventional full-wave rectifier?

A14. The peak voltage is half that of a half-wave rectifier. Q15. What main advantage does a bridge rectifier have over a conventional full-wave rectifier? A15. The bridge rectifier can produce double the voltage with the same size transformer. Q16. If you increase the value of the capacitor will the XC increase or decrease? Why?

A16. Decrease-Capacitance is inversely proportional to XC.

Q17. What is the most basic type of filter?

A17. Capacitor. Q18. In a capacitor filter, is the capacitor in series or parallel with the load?

A18. Parallel. Q19. Is better filtering achieved at a high frequency or at a low frequency at the input of the filter?

A19. High. Q20. Does a filter circuit increase or decrease the average output voltage?

A20. Increase. Q21. What determines the rate of discharge of the capacitor in a filter circuit?

A21. Value of capacitance and load resistance.

Q22. Does low ripple voltage indicate good or bad filtering?

A22. Good. Q23. Is a full-wave rectifier output easier to filter than that of a half-wave rectifier?

A23. Yes. Q24. In an LC choke-input filter, what prevents the rapid charging of the capacitor?

A24. Counter electro-motive force of the inductor.

Q25. What is the value usually chosen for a filter choke?

A25. 1 to 20 henries. Q26. If the inductance of a choke-input filter is increased, will the output ripple voltage amplitude (Er) increase or decrease?

A26. Decrease. Q27. Is an RC filter used when a large current or a small current demand is required?

A27. Small. Q28. Why is the use of large value capacitors in filter circuits discouraged?

A28. Expense.

Q29. When is a second RC filter stage used?

A29. When ripple must be held at an absolute minimum.

Q30. What is the most commonly used filter in use today?

A30. LC capacitor-input filter. Q31. What are the two main disadvantages of an LC capacitor filter?

A31. Cost of the inductor and size of the inductor.

Q32. What two factors can cause output dc voltage to change?

A32. Ac line voltage and a change in load resistance. Q33. What is the commonly used figure of merit for a power supply?

A33. Percent of regulator. Q34. If a power supply produces 20 volts with no load and 15 volts under full load, what is the percent of regulation?

A34. 33.33%

Q35. What percent of regulation would be ideal?

A35. 0%. Q36. The purpose of a voltage regulator is to provide an output voltage with little or no ____.

A36. Variation.

NEETS Q&A

Q37. The two basic types of voltage regulators are _______ and _______.

A37. Series and shunt. Q38. When a series voltage regulator is used to control output voltages, any increase in the input voltage results in an increase/a decrease in the resistance of the regulating device.

A38. Increase. Q39. A shunt type voltage regulator is connected in series/parallel with the load resistance.

A39. Parallel. Q40. In an electron tube regulator, the electron tube replaces what component?

A40. Variable resistor.

Q41. What is the purpose of the amperite regulator?

A41. Current regulation. Q42. As the tube filaments in the load heat up, will the circuit current increase or decrease?

A42. Decrease. Q43. What is the most important thing to remember when troubleshooting?

A43. Safety precautions. Q44. What is the main reason for grounding the return side of the transformer to the chassis?

A44. Reduce the cost of manufacturing equipment. Q45. What are two types of checks used in troubleshooting power supplies?

A45. Visual and signal tracing.

PRINCIPLES OF TRANSMISSION LINES

Q1. What connecting link is used to transfer energy from a radio transmitter to its antenna located on

A1. Transmission line. Q2. What term is used for the end of the transmission line that is connected to a transmitter? A2. Input end, generator end, transmitter end, sending end, and source. Q3. What term is used for the end of the transmission line that is connected to an antenna?

A3. Output end, receiving end, load end and sink.

Q4. List the five types of transmission lines in use today. A4. Parallel two-wire, twisted pair, shielded pair, coaxial line and waveguide. Q5. Name two of the three described uses of a two-wire open line.

A5. Power lines, rural telephone lines, and telegraph lines. Q6. What are the two primary disadvantages of a two-wire open line?

A6. High radiation losses and noise pickup. Q7. What type of transmission line is often used to connect a television set to its antenna?

A7. Twin lead.

Q8. What is the primary advantage of the shielded pair?

A8. The conductors are balanced to ground.

Q9. What are the two types of coaxial lines in use today?

A9. Air coaxial (rigid) and solid coaxial (flexible).

Q10. What is the chief advantage of the air coaxial line?

A10. The ability to minimize radiation losses.

Q11. List the three disadvantages of the air coaxial line. A11. Expensive to construct, must be kept dry, and high frequency losses limit the practical length of the line.

Q12. List the two common types of waveguides in use today.

A12. Cylindrical and rectangular. Q13. What are the three types of line losses associated with transmission lines?

A13. Copper, dielectric, and radiation. Q14. Losses caused by skin effect and the I2R (power) loss are classified as what type of loss?

A14. Copper losses. Q15. What types of losses cause the dielectric material between the conductors to be heated?

A15. Dielectric losses. Q16. What must the physical length of a transmission line be if it will be operated at 15,000,000 Hz?

A16. λ = 20 meters Q17. What are two of the three physical factors that determine the values of capacitance and inductance of a transmission line? A17. (1) Type of line used, (2) dielectric in the line, and (3) length of line.

Q18. A transmission line is said to have distributed constants of inductance, capacitance, and resistance along the line. What units of measurement are used to express these constants? A18. Inductance is expressed in micro henrys per unit length, capacitance is expressed in picofarads per unit length, and resistance is expressed in ohms per unit length. Q19. Describe the leakage current in a transmission line and in what unit it is expressed. A19. The small amount of current that flows through the dielectric between two wires of a transmission line and is expressed in micro ohms per unit length. Q20. All the power sent down a transmission line from a transmitter can be transferred to an antenna under what optimum conditions? A20. When the characteristic impedance of the transmission line and the load impedance are equal. Q21. What symbol is used to designate the characteristic impedance of a line, and what two variables does it compare?

A21. Z0 and it is the ratio of E to I at every point along the line. Q22. What is the range of the characteristic impedance of lines used in actual practice?

A22. Between 50 and 600 ohms. Q23. Two types of waves are formed on a transmission line. What names are given to these waves? A23. Incident waves from generator to load. Reflected waves from load back to generator. Q24. In figure 3-27, which waveforms on the left have a resultant wave of zero, and what is indicated by these waves? A24. 2 and 6 have zero resultant wave and they indicate that the incident and reflected waves are 180 degrees out of phase at all parts. Q25. On an open-ended transmission line, the voltage is always zero at what distance from each end of the line?

A25. One-fourth the distance from each end of the line. Q26. A non-resonant line is a line that has no standing waves of current and voltage on it and is considered to be flat. Why is this true?

A26. The load impedance of such a line is equal to Z0. Q27. On an open line, the voltage and impedance are maximum at what points on the line?

A27. Even quarter-wave points (1/2λ, 1λ, 3/2λ…) Q28. At what point on an open-circuited rf line do voltage peaks occur? A28. At 1/2 wavelength from the end and at every 1/2 wavelength along the line. Q29. What is the square of the voltage standing-wave ratio called?

A29. Power standing-wave ratio (pswr).

Q30. What does vswr measure?

A30. The existence of voltage variations on a line.

QUANTITATIVE MEASUREMENTS

Q-1. What conditions must be met in order to balance a bridge circuit? A-1. A bridge circuit is balanced when the opposite legs of the comparing and measuring circuits exhibit the same voltage drop. Q-2. When you are measuring a component using a bridge, what is the most common cause of inaccurate measurements?

A-2. The capacitive and inductive characteristics of the test leads. Q-3. How does the supply voltage affect the accuracy of Wheatstone bridge measurements? A-3. As the supply voltage increases, bridge components may heat up and become less accurate. Q-4. Kelvin bridges are well suited for what type of measurements?

A-4. Small values of resistances. Q-5. When you are testing an inductor with a Hay bridge, the characteristics of the inductor are compared with what type of device?

A-5. A standard capacitor. Q-6. What do impedance-angle meters and vector bridges have in common? A-6. Both measure phase angle and magnitude in determining impedance. Q-7. What is the result of an impedance mismatch between a receiver or transmitter and its transmission line or antenna? A-7. High vswr, which equates to poor reception or a loss of power output. Q-8. What are the three units of measure most commonly used when referring to af power measurements?

A-8. DB, dBm, and vu. Q-9. In reference to dB meters, 0 dBm represents 1 milliwatt into what value of load?

A-9. 600-ohm load.

NEETS Q&A

Q-10. What is the main difference between a vu and a dB meter? A-10. DB meters are used for measuring sine waves. Vu meters are used to measure the average value of complex waveforms. Q-11. What type of device is used to extend the current-measuring capability of electrodynamic wattmeters?

A-11. Current transformers. Q-12. For power measurements, what advantage does an electronic wattmeter have over an electrodynamic wattmeter? A-12. Electronic wattmeters are capable of measuring high-fequency signals. Q-13. What is the advantage of using in-line wattmeters over output power meters? A-13. Most in-line wattmeters are capable of measuring both forward and reflected power. Q-14. What type of material is used in the construction of bolometers and thermistors? A-14. Temperature-sensitive material that exhibits a large negative temperature coefficient. Q-15. Power measurements performed with calorimeters are based on what three variables?

A-15. Temperature, mass, and time.

Q-16. What is the result of applying power to a calorimeter? A-16. As power is applied, the medium heats up in proportion to the applied power. Q-17. What government agency is responsible for monitoring our primary frequency standards?

A-17. The National Bureau of Standards. Q-18. What is the primary measurement application for tuning forks?

A-18. They are used to monitor fixed motor speeds. Q-19. If you are required to monitor the speed of a device with a stroboscope over an extended period of time, what step should be taken to prolong the life of the flasher tube?

A-19. Monitor a submultiple frequency to prolong the flasher-tube life. Q-20. What happens when a frequency meter is adjusted to the frequency of the signal being measured? A-20. Power is absorbed by the frequency meter cavity; and a pronounced dip in power, at the output, will be observed.

QUALITATIVE MEASUREMENTS

Q-1. At what points along a transmission line will a neon lamp glow the brightest?

A-1. At standing-wave voltage peaks. Q-2. What vswr is a perfect match between a transmitter and its load?

A-2. 1 to 1. Q-3. What are the two common causes of transmission-line deterioration?

A-3. Corrosive effects of salt water and weather extremes. Q-4. Is it possible for a transmission line to operate improperly at certain frequencies and properly at others?

A-4. Yes, it is quite common. Q-5. What factor has the greatest effect on the physical size of a coaxial cable?

A-5. The dielectric constant of the insulating material. Q-6. Is the attenuation of a coaxial cable independent of frequency?

A-6. No.

Q-7. What is the main cause of intermodulation distortion?

A-7. Close spacing of transmitters and receivers. Q-8. When you are testing a piece of equipment for intermodulation distortion, what should the output of the equipment look like?

A-8. An exact reproduction of the input.

RADAR FUNDAMENTALS

Q1. Radar surface-angular measurements are referenced to true north and measured in what plane?

A1. Horizontal plane. Q2. The distance from a radar set to a target measured along the line of sight is identified by what term?

A2. Range. Q3. What is the speed of electromagnetic energy traveling through air? A3. Approximately the speed of light (162,000 nautical miles per second). Q4. How much time is required for electromagnetic energy to travel 1 nautical mile and return to the source?

A4. 12.36 microseconds. Q5. In addition to recovery time, what determines the minimum range of a radar set?

A5. Pulse width. Q6. Atmospheric interference with the travel of electromagnetic energy increases with what rf energy characteristic?

A6. Frequency.

Q7. How is prt related to prf?

A7. prfprt

1=

Q8. What type of radar transmitter power is measured over a period of time?

A8. Average power. Q9. What term is used to describe the product of pulse width and pulse-repetition frequency?

A9. Duty cycle.

Q10. What type of target bearing is referenced to your ship?

A10. Relative bearing.

Q11. What type of radar detects range, bearing, and height?

A11. Three-dimensional. Q12. What characteristic(s) of radiated energy is (are) altered to achieve electronic scanning?

A12. Frequency or phase. Q13. What term is used to describe the ability of a radar system to distinguish between targets that are close together?

A13. Target resolution.

Q14. The degree of bearing resolution for a given radar system depends on what two factors?

A14. Beam width and range. Q15. What happens to the speed of electromagnetic energy traveling through air as the altitude increases?

A15. Speed increases. Q16. What term is used to describe a situation in which atmospheric temperature first increases with altitude and then begins to decrease?

A16. Temperature inversion. Q17. What radar subsystem supplies timing signals to coordinate the operation of the complete system?

A17. Synchronizer. Q18. When a transmitter uses a high-power oscillator to produce the output pulse, what switches the oscillator on and off?

A18. High-voltage pulse from the modulator. Q19. What radar component permits the use of a single antenna for both transmitting and receiving?

A19. Duplexer.

Q20. What is the simplest type of scanning?

A20. Single lobe. Q21. How does the operator of a single-lobe scanning system determine when the target moves off the lobe axis?

A21. The reflected signals decrease in strength.

Q22. What are the two basic methods of scanning?

A22. Mechanical and electronic. Q23. Rotation of an rf-feed source to produce a conical scan pattern is identified by what term?

A23. Nutation.

Q24. The Doppler effect causes a change in what aspect of rf energy that strikes a moving object?

A24. Frequency.

Q25. The Doppler variation is directly proportional to what radar contact characteristic?

A25. Velocity. Q26. The Doppler method of object detection is best for what type objects?

A26. Fast-moving targets. Q27. The beat frequency in a swept-frequency transmitter provides what contact information?

A27. Range. Q28. What factor determines the difference between the transmitted frequency and the received frequency in an fm transmitter?

A28. Travel time. Q29. What type of objects are most easily detected by an fm system?

A29. Stationary. Q30. What transmission method does NOT depend on relative frequency or target motion?

A30. Pulse modulation.

Q31. What transmission method uses a stable cw reference oscillator, which is locked in phase with the transmitter frequency?

NEETS Q&A

A31. Pulse-Doppler. Q32. What type of radar provides continuous range, bearing, and elevation data on an object?

A32. Track radar.

Q33. Radar altimeters use what type of transmission signal?

A33. Frequency modulated (fm). Q34. A surface-search radar normally scans how many degrees of azimuth?

A34. 360 degrees.

Q35. What limits the maximum range of a surface-search radar?

A35. Radar horizon.

Q36. What is the shape of the beam of a surface-search radar?

A36. Wide vertically, narrow horizontally.

Q37. Air-search radar is divided into what two basic categories?

A37. 2D and 3D.

Q38. What position data are supplied by 2D search radar?

A38. Range and bearing. Q39. Why do 2D air-search radars use relatively low carrier frequencies and low pulse-repetition rates?

A39. Increased maximum range.

Q40. Why is the range capability of 3D radar usually less than the range of 2D radar?

A40. Higher operating frequency. Q41. Fire-control tracking radar most often radiates what type of beam?

A41. A narrow circular beam. Q42. Tracking radar searches a small volume of space during which phase of operation?

A42. Acquisition. Q43. What width is the pulse radiated by fire-control tracking radar?

A43. Very narrow.

Q44. Which beam of missile-guidance radar is very wide?

A44. Capture beam.

RADAR INDICATORS AND ANTENNAS

Q1. What are the three fundamental quantities involved in radar displays?

A1. Range, bearing, and elevation. Q2. What are the required radar inputs for proper indicator operation?

A2. Triggers, video, and antenna information.

Q3. What coordinates are displayed on an rhi scope?

A3. Range and elevation.

Q4. What coordinates are presented on a ppi scope?

A4. Range and bearing.

Q5. What type of deflection is preferred for a crt electron beam?

A5. Electromagnetic.

Q6. Which of the two types of deflection coils (fixed or rotating) is used most often?

A6. Fixed.

Q7. What type of ranging circuit is most often used with a radar that requires extremely accurate range data?

A7. Range gate or range step. Q8. The range sweep in a range-gate generator is started at the same time as what other pulse?

A8. Transmitter. Q9. Range-marker generators produce pulses based on what radar constant?

A9. The radar mile (12.36 microseconds). Q10. What radar scope uses a range step for range measurement?

A10. The A scope.

Q11. Which of the two general classes of antennas is most often used with radar?

A11. Directional. Q12. The power gain of an antenna is directly related to what other antenna property?

A12. Directivity. Q13. A parabolic reflector changes a spherical wavefront to what type of wavefront?

A13. Plane. Q14. How many major lobes are produced by a paraboloid reflector?

A14. One.

Q15. What type of radiator normally drives a corner reflector?

A15. Half-wave. Q16. The broadside array consists of a flat reflector and what other elements?

A16. Two or more half-wave dipoles. Q17. Horn radiators serve what purpose other than being directional radiators?

A17. Waveguide impedance matching devices.

RADAR SUBSYSTEMS

Q1. What is the purpose of the synchronizer in a radar system?

A1. Controls system operation and timing.

Q2. What is the purpose of the majority of circuits in a radar system?

A2. Timing and control.

Q3. A self-synchronized radar system obtains timing trigger pulses from what source?

A3. Transmitter. Q4. What type of multivibrator can be used as a radar master oscillator?

A4. Free-running. Q5. In an externally synchronized radar, what determines the prr of the transmitter?

A5. The master oscillator. Q6. In figure 2-1, what causes the initial and final pulses on the receiver output signal?

A6. Leakage from the duplexer.

Q7. What basic circuits meet the requirements of an externally synchronized master oscillator? A7. Sine-wave oscillator, single-swing blocking oscillator, and master-trigger (astable) multivibrator.

Q8. Name a disadvantage of sine-wave oscillator synchronizers.

A8. It requires additional shaping circuits. Q9. Which of the basic timing circuits produces sharp trigger pulses directly?

A9. Blocking oscillators.

Q10. What are the two basic types of transmitters?

A10. Keyed oscillator and power-amplifier chain.

Q11. What controls transmitter pulse width?

A11. The modulator.

Q12. In addition to a flat top, what characteristics must a modulator pulse have?

A12. Steep leading and trailing edges. Q13. What type of modulator is most commonly used in modern radar systems?

A13. Line-pulsed. Q14. What three types of storage elements most often are used in modulators?

A14. Capacitor, artificial transmission line, or pulse-forming network. Q15. What characteristic is determined by the time required for a voltage wave to travel from the input end of an artificial transmission line to the output end and back again?

A15. Pulse width. Q16. What type of tube best meets the requirements of a modulator switching element?

A16. Thyratron.

Q17. What modulator element controls the rate at which the storage element charges?

A17. The charging impedance.

Q18. What is the frequency range of magnetron oscillators?

A18. 600-30,000 megahertz.

Q19. What two forms of instability are common in magnetrons?

A19. Mode skipping and mode shifting. Q20. What is the effect on magnetron operation if the magnetic field strength is too high?

A20. The magnetron will not oscillate.

Q21. What is the typical frequency range about the center frequency of a tunable magnetron?

A21. ±5 percent.

Q22. What is the primary advantage of power-amplifier transmitters over keyed-oscillator transmitters?

A22. Frequency stability. Q23. In the power amplifier shown in figure 2-10, what two signals are mixed to produce the output signal?

A23. Local oscillator and coherent oscillator.

Q24. What type of klystron is used as the final stage of a power-

NEETS Q&A

amplifier transmitter?

A24. Multicavity klystron. Q25. What transmitter component allows the radiation of a large number of discrete frequencies over a wide band?

A25. Frequency synthesizer. Q26. What is the result of pulsing a pulsed rf amplifier when no rf is present?

A26. Oscillations at an undesired frequency.

Q27. What type of switches are used as duplexers?

A27. Electronic. Q28. What tube in a duplexer has the primary function of disconnecting the receiver?

A28. Tr tube.

Q29. How may the tr tube ionization speed be increased?

A29. Apply keep-alive voltage. Q30. The actions of the tr and atr circuits depend on the impedance characteristics of what length of transmission line?

A30. Quarter-wavelength section.

Q31. During which of the transmit or receive cycles are both the tr and atr tubes of a parallelconnected duplexer ionized (arcing)?

A31. Transmit.

Q32. In a series-connected duplexer, what tube (tr or atr), if any, fires during the receive cycle?

A32. Neither fires. Q33. To propagate energy down an arm of a hybrid ring duplexer, the two fields at the junction of the arm and the ring must have what phase relationship?

A33. 180 degrees out of phase. Q34. What is the greatest limiting factor in a receiver’s detectable range?

A34. Noise.

Q35. What type of receiver is most often used in radar systems?

A35. Superheterodyne.

Q36. What IF frequencies are normally used in radar receivers?

A36. Thirty or sixty megahertz.

Q37. Which component of the receiver produces the signal that is mixed with the received signal to produce the IF signal?

A37. Local oscillator.

Q38. What receiver circuit actually produces the IF frequency?

A38. Mixer.

Q39. The IF amplifiers are connected in what amplifier configuration?

A39. Cascade.

Q40. Which receiver component converts the IF pulses to video pulses?

A40. Detector. Q41. Which of the two types of automatic gain control, agc or iagc, is most effective in radar use for the Navy?

A41. IAGC. Q42. Immediately after the transmitter fires, stc reduces the receiver gain to what level?

A42. Zero.

Q43. How does ftc affect receiver gain, if at all?

A43. FTC has no effect on receiver gain. Q44. What type of target has a fixed phase relationship from one receiving period to the next?

A44. Stationary. Q45. What signal is used to synchronize the coherent oscillator to a fixed phase relationship with the transmitted pulse?

A45. Coho lock pulse.

Q46. What is the phase relationship between the delayed and undelayed video?

A46. Opposite.

Q47. When a large signal and a small signal are applied to a lin-log amplifier at the same time, what is the effect on the small signal?

A47. Amplification is reduced.

Q48. What happens to the overall gain of a lin-log amplifier as each stage saturates?

A48. Decreases.

Q49. A monopulse receiver has how many separate channels?

A49. Three.

Q50. If a target is on the bearing axis of the radiated beam, what is the input to the bearing IF channel?

A50. Zero. Q51. What characteristic of the bearing and elevation output signals determines the direction of antenna movement?

A51. Phase.

RADAR SYSTEM MAINTENANCE

Q1. The spectrum of a radar transmitter describes what characteristic of the output pulse?

A1. Frequency distribution. Q2. Where should the transmitter spectrum be located with respect to the receiver response curve?

A2. In the center. Q3. The ideal radar spectrum has what relationship to the carrier frequency?

A3. Symmetrical above and below the carrier frequency.

Q4. The display screen of a spectrum analyzer presents a graphic plot of what two signal characteristics?

A4. Power and frequency.

Q5. The peak power of a radar depends on the interrelationship of what other factors?

A5. Average power, pulse width, and prt. Q6. Transmitter power readings are most often referenced to what power level?

A6. 1 milliwatt. Q7. A loss of receiver sensitivity has the same effect on range performance as what other loss?

A7. Transmitter power loss. Q8. You determine receiver sensitivity by measuring the power level of what signal?

A8. Minimum discernible signal (mds).

Q9. When measuring receiver sensitivity, what quantities must you add to the dBm reading obtained on the signal generator or test set?

A9. Attenuations of the directional coupler and the connecting cable. Q10. Receiver bandwidth is defined as those frequencies spread between what two points of the receiver response curve?

A10. Half-power points.

Q11. The end of the usefulness of a tr tube is indicated by an increase in what quantity?

A11. Recovery time. Q12. Most shipboard distribution systems use ac power that has what number of phases?

A12. Three. Q13. How is emergency power applied when normal power is lost?

A13. Automatically. Q14. What device is used to switch power from the normal source to an alternate source for nonvital users?

A14. Manual bus transfer (MBT) unit.

Q15. What procedure should you use when a power input to your equipment is missing?

A15. Work backwards from the load to the source.

Q16. What is the normal source of dry air for a radar system?

A16. Ship's central dry-air system.

Q17. What is the major difference between the electronics dry-air branch and the vital service lp air main?

A17. Degree of dehydration.

Q18. What is the air control panel designed to control?

A18. Pressure. Q19. What type of cooling is used to control ambient room temperature?

A19. Air conditioning.

Q20. A typical liquid-cooling system is composed of what loops?

A20. Primary and secondary. Q21. What loop of a cooling system is often supplied by sea water?

A21. The primary loop.

RADIO WAVE PROPAGATION

Q1. Which two composite fields (composed of E and H fields) are associated with every antenna?

A1. Induction field and radiation field. Q2. What composite field (composed of E and H fields) is found stored in the antenna?

A2. Induction field. Q3. What composite field (composed of E and H fields) is propagated into free space?

A3. Radiation field. Q4. What is the term used to describe the basic frequency of a radio wave?

NEETS Q&A

A4. Fundamental frequency. Q5. What is the term used to describe a whole number multiple of the basic frequency of a radio wave?

A5. Harmonic frequency or harmonics. Q6. It is known that WWV operates on a frequency of 10 megahertz. What is the wavelength of WWV?

A6. 30 meters. Q7. A station is known to operate at 60-meters. What is the frequency of the unknown station?

A7. 5 megahertz. Q8. If a transmitting antenna is placed close to the ground, how should the antenna be polarized to give the greatest signal strength?

A8. Vertically polarized. Q9. In the right-hand rule for propagation, the thumb points in the direction of the E field and the forefinger points in the direction of the H field. In what direction does the middle finger point?

A9. Direction of wave propagation. Q10. What is one of the major reasons for the fading of radio waves which have been reflected from a surface?

A10. Shifting in the phase relationships of the wave.

Q11. What are the three layers of the atmosphere?

A11. Troposphere, stratosphere, and ionosphere. Q12. Which layer of the atmosphere has relatively little effect on radio waves?

A12. Stratosphere. Q13. What is the determining factor in classifying whether a radio wave is a ground wave or a space wave? A13. Whether the component of the wave is travelling along the surface or over the surface of the earth. Q14. What is the best type of surface or terrain to use for radio wave transmission?

A14. Radio horizon is about 1/3 farther. Q15. What is the primary difference between the radio horizon and the natural horizon?

A15. Sea water. Q16. What three factors must be considered in the transmission of a surface wave to reduce attenuation? A16. (a) electrical properties of the terrain (b) frequency (c) polarization of the antenna

Q17. What causes ionization to occur in the ionosphere?

A17. High energy ultraviolet light waves from the sun. Q18. How are the four distinct layers of the ionosphere designated?

A18. D, E, F1, and F2 layers. Q19. What is the height of the individual layers of the ionosphere? A19. D layer is 30-55 miles, E layer 55-90 miles, and F layers are 90-240 miles. Q20. What factor determines whether a radio wave is reflected or refracted by the ionosphere?

A20. Thickness of ionized layer. Q21. There is a maximum frequency at which vertically transmitted radio waves can be refracted back to Earth. What is this maximum frequency called?

A21. Critical frequency. Q22. What three main factors determine the amount of refraction in the ionosphere? A22. (a) density of ionization of the layer (b) frequency (c) angle at which it enters the layer

Q23. What is the skip zone of a radio wave? A23. A zone of silence between the ground wave and sky wave where there is no reception. Q24. Where does the greatest amount of ionospheric absorption occur in the ionosphere?

A24. Where ionization density is greatest.

Q25. What is meant by the term "multipath"? A25. A term used to describe the multiple patterns a radio wave may follow. Q26. When a wide band of frequencies is transmitted simultaneously, each frequency will vary in the amount of fading. What is this variable fading called?

A26. Selective fading. Q27. What are the two main sources of emi with which radio waves must compete?

A27. Natural and man-made interference. Q28. Thunderstorms, snowstorms, cosmic sources, the sun, etc., are a few examples of emi sources. What type of emi comes

from these sources?

A28. Natural. Q29. Motors, switches, voltage regulators, generators, etc., are a few examples of emi sources. What type of emi comes from these sources?

A29. Man-made. Q30. What are three ways of controlling the amount of transmitter-generated emi? A30. (a) filtering and shielding of the transmitter (b) limiting bandwidth (c) cutting the antenna to the Q31. What are three ways of controlling radiated emi during transmission? A31. (a) physical separation of the antenna (b) limiting bandwidth of the antenna (c) use of directional antennas Q32. What are the two general types of variations in the ionosphere?

A32. Regular and irregular variations. Q33. What is the main difference between these two types of variations? A33. Regular variations can be predicted but irregular variations are unpredictable. Q34. What are the four main classes of regular variation which affect the extent of ionization in the ionosphere?

A34. Daily, seasonal, 11-year, and 27-days variation. Q35. What are the three more common types of irregular variations in the ionosphere?

A35. Sporadic E, sudden disturbances, and ionospheric storms.

Q36. What do the letters muf, luf, and fot stand for? A36. Muf is maximum usable frequency. Luf is lowest usable frequency. Fot is commonly known as optimum working frequency.

Q37. When is muf at its highest and why? A37. Muf is highest around noon. Ultraviolet light waves from the sun are most intense.

Q38. What happens to the radio wave if the luf is too low?

A38. When luf is too low it is absorbed and is too weak for reception. Q39. What are some disadvantages of operating transmitters at or near the luf? A39. Signal-to-noise ratio is low and the probability of multipath propagation is greater. Q40. What are some disadvantages of operating a transmitter at or near the muf?

A40. Frequent signal fading and dropouts.

Q41. What is fot? A41. Fot is the most practical operating frequency that can be relied on to avoid problems of multipath,

Q42. How do raindrops affect radio waves?

A42. They can cause attenuation by scattering. Q43. How does fog affect radio waves at frequencies above 2 gigahertz?

A43. It can cause attenuation by absorbtion. Q44. How is the term "temperature inversion" used when referring to radio waves? A44. It is a condition where layers of warm air are formed above layers of cool air.

Q45. How does temperature inversion affect radio transmission? A45. It can cause vhf and uhf transmission to be propagated far beyond normal line-of-sight distances. Q46. In what layer of the atmosphere does virtually all weather phenomena occur?

A46. Troposphere. Q47. Which radio frequency bands use the tropospheric scattering principle for propagation of radio waves?

A47. Vhf and above. Q48. Where is the tropospheric region that contributes most strongly to tropospheric scatter propagation? A48. Near the mid-point between the transmitting and receiving antennas, just above the radio horizon.

SCHEMATIC READING

Q1. Why must cables and wires be identified? A1. To provide the technician with a means to trace the wires when troubleshooting and repairing electrical and electronic systems.

Q2. Where would you find the wire identification system for a specific piece of equipment?

A2. In the technical manual for the equipment.

Q3. What does the cable number identify?

A3. Individual cable in a specific circuit.

Q4. If a wire passes through a connector what portion of the aircraft wire identification number changes?

A4. Wire segment letter.

NEETS Q&A

Q5. What markings are found on spaghetti sleeving?

A5. The conductor connections both "to" and "from." Q6. What is the purpose of the green conductor in a power tool or electrical appliance cable? A6. To prevent electrical shock to the operator in case there is an electrical short to the frame of the appliance or too. Q7. What type of electrical diagram is used to identify the components of a system?

A7. A pictorial diagram. Q8. What type of diagram is used to find the location of a component?

A8. An isometric diagram. Q9. What types of diagrams are the most convenient from which to learn the basic Functions of a circuit?

A9. Block or single-line diagram. Q10. What type of diagram is the most useful in learning the overall operation of a system?

A10. A schematic diagram.

Q11. Refer to the schematic diagram in figure 3-10. If the ignition switch is placed in the ON position and all the engine instruments operate properly except the gas gauge, where would the fault probably be?

A11. Between point (3) and the gas gauge tank unit ground. Q12. If the fuse shown on the schematic (figure 3-10) opens, what lights will operate?

A12. Only the brake lights.

Q13. What type of diagram is the most detailed?

A13. Wiring diagram. Q14. Why must a wiring diagram be used in conjunction with a schematic to troubleshoot a system?

A14. To find the test points. Q15. What type of diagram would be most useful for wiring a relay into a circuit?

A15. Terminal diagram.

Q16. What safety precaution must you observe when soldering or hot-wire stripping fluoroplastic insulated wire?

A16. Adequate ventilation.

Q17. What must be used to test an activated circuit?

A17. Approved meters or other indicating devices.

Q18. How should excess solder be removed from a hot soldering iron?

A18. By use of a cleaning cloth.

SEMICONDUCTOR DIODES

Q1. What is a solid-state device? A1. An electronic device that operates by virtue of the movement of electrons within a solid piece of semiconductor material.

Q2. Define the term negative temperature coefficient. A2. It is the decrease in a semiconductor’s resistance as temperature rises.

Q3. Name three of the largest users of semiconductor devices.

A3. Space systems, computers, and data processing equipment.

Q4. State one requirement of an electron tube, which does not exist for semiconductors, that makes the tube less efficient than the semiconductor. A4. The electron tube requires filament or heater voltage, whereas the semiconductor device does not; consequently, no power input is spent by the semiconductor for conduction.

Q5. Define matter and list its three different states. A5. Anything that occupies space and has weight. Solid, liquid, and gas. Q6. What is the smallest particle into which an element can be broken down and still retain all its original properties?

A6. The atom. Q7. What are the three particles that comprise an atom and state the type of charge they hold?

A7. Electrons-negative, protons-positive, and neutrons-neutral.

Q8. What is the outer shell of an atom called?

A8. The valence shell. Q9. What term is used to describe the definite discrete amounts of energy required to move an electron from a low shell to a higher shell?

A9. Quanta.

Q10. What is a negative ion? A10. A negatively charged atom having more than its normal amount of electrons. Q11. What is the main difference in the energy arrangement between an isolated atom and the atom in a solid?

A11. The energy levels of an atom in a solid group together to form

energy bands, whereas the isolated atom does not.

Q12. What determines, in terms of energy bands, whether a substance is a good insulator, semiconductor, or conductor?

A12. The width of the forbidden band.

Q13. What determines the chemical activity of an atom?

A13. The number of electrons in the valence shell. Q14. What is the term used to describe the sharing of valence electrons between two or more atoms?

A14. Covalent bonding.

Q15. Name the two types of current flow in a semiconductor.

A15. Electron flow and hole flow. Q16. What is the name given to a piece of pure semiconductor material that has an equal number of electrons and holes?

A16. Intrinsic. Q17. What is the name given to a doped germanium crystal with an excess of free holes?

A17. P-type crystal.

Q18. What are the majority carriers in an N-type semiconductor?

A18. Electrons.

Q19. What is the purpose of a PN junction diode?

A19. To convert alternating current into direct current. Q20. In reference to the schematic symbol for a diode, do electrons flow toward or away from the arrow?

A20. Toward the arrow. Q21. What type of PN diode is formed by using a fine metal wire and a section of N-type semiconductor material?

A21. Point-contact.

Q22. What are the majority carriers in a P-type semiconductor?

A22. Holes. Q23. Conduction in which type of semiconductor material is similar to conduction in a copper wire?

A23. N-type material.

Q24. What is the name of the area in a PN junction that has a shortage of electrons and holes?

A24. Depletion region.

Q25. In order to reverse bias in a PN junction, what terminal of a battery is connected to the P material?

A25. Negative.

Q26. What type of bias opposes the PN junction barrier?

A26. Forward.

Q27. What is a load?

A27. Any device that draws current.

Q28. What is the output of a half-wave rectifier?

A28. A pulsating dc voltage. Q29. What type of rectifier is constructed by sandwiching a section of semiconductor material between two metal plates?

A29. Metallic rectifier.

Q30. What type of bias makes a diode act as a closed switch?

A30. Forward bias. Q31. What is used to show how diode parameters vary over a full operating range?

A31. A characteristic curve.

Q32. What is meant by diode ratings? A32. They are the limiting values of operating conditions outside which operations could cause diode damage. Q33. What does the letter "N" indicate in the semiconductor identification system?

A33. A semiconductor.

Q34. What type of diode has orange, blue, and gray bands?

A34. 1N368.

Q35. What is the greatest threat to a diode?

A35. Heat. Q36. When checking a diode with an ohmmeter, what is indicated by two high resistance measurements?

A36. The diode is open or has a high-forward resistance.

SERVOS

Q-1. What is a servo? A-1. A system in which the precise movement of a large load is controlled by a relatively weak control signal. Q-2. In an open-loop control system, what action reduces the input to zero so the load is stopped at the desired position?

A-2. Usually the operator senses the desired load movement and

NEETS Q&A

reduces the input to stop the motor.

Q-3. What basic requirement of a closed-loop system (not present in open-loops) enables present load position to be sensed?

A-3. Feedback. Q-4. An error signal is the difference between what two quantities fed to the CT (error detector)?

A-4. Input signal and feedback. Q-5. What are the two functions of the servo motor in the system shown in figure 2-2? A-5. To move the load and provide feedback data to the error detector. Q-6. What are the three relatively common classifications of servo systems by function? A-6. Classifications in accordance with position, velocity, and acceleration functions. Q-7. The output of the sum point must contain information that controls what two factors of load movement in a position servo?

A-7. Amount and direction of rotation. Q-8. What term is used for a series of overshoots in a servo system?

A-8. Hunting. Q-9. What are two major differences between velocity servos and position servos? A-9. Velocity loop senses velocity rather than position. When velocity loop is nulled, an error signal is still present and the load continues to move. Q-10. In a typical velocity servo block diagram what device is placed in the feedback loop that is not present in the position servo?

A-10. Tachometer. Q-11. What is the advantage of using a closed-servo loop to control load velocity? A-11. The closed-servo loop can regulate load speed under changing conditions. Q-12. If a position servo system tends to oscillate whenever a new position is selected, is the system overdamped or underdamped?

A-12. Underdamped. Q-13. If a position servo system does not respond to small changes of the input, is the system overdamped or underdamped?

A-13. Overdamped.

Q-14. Why is damping needed in a practical servo system?

A-14. To minimize overshoot and/or oscillations. Q-15. Error-rate damping is effective because the circuitry has the capability of ______________the amount of overshoot before it happens.

A-15. Anticipating. Q-16. In a properly designed servo system that has an oscillating input (order), what should be the response of the load?

A-16. It should oscillate. Q-17. What is the advantage of designing a limited bandwidth into a servo amplifier?

A-17. Unwanted noise-generated frequencies are rejected. Q-18. When the input and output wipers of a balanced potentiometer are in the same angular position, what is the value of the error voltage?

A-18. Zero. Q-19. In the output of an ac error detector, what indicates the (a) direction and (b) amount of control necessary for correspondence?

A-19. (a) Phase. (b) Amplitude. Q-20. What two basic types of magnetic devices are used as error detectors?

A-20. E-transformer and control transformers. Q-21. What is the basic difference between the primaries of ac and dc rate generators?

A-21. The method of primary excitation (ac and permanent magnet).

Q-22. What is the purpose of a modulator in a servo system?

A-22. To convert a dc error signal into an ac error signal.

Q-23. What is the purpose of a demodulator in a servo system?

A-23. To convert an ac error signal into a dc error signal. Q-24. What is the purpose of a synchronizing network in a servo system? A-24. To switch control of the amplifier between either the coarse signal and the fine error signal. Q-25. What the three basic components make up the typical magnetic amplifier?

A-25. Two saturable reactors and a transformer.

SOFTWARE

Q-1. What is the heart of any computer system?

A-1. The operating system. Q-2. Which types of operating systems are the simplest and most common on microcomputers?

A-2. Single user/single tasking. Q-3. What types of operating systems let more than one user access the same resources at the same time?

A-3. Multiuser/multitasking. Q-4. Why is the availability of applications software for a particular operating system critical? A-4. Because, to use applications software, it must be compatible with the operating system. Q-5. How is the applications software compatibility problem overcome? A-5. Some software comes in several versions so it can run under several different operating systems.

Q-6. What programs eliminate the need for programmers to write new programs when all they want to do is copy, print, or sort a data file?

A-6. Utility programs.

Q-7. How do we tell a utility program what we want it to do? A-7. By providing information about files, data fields, and the process to be used.

Q-8. What is the term given to arranging data records in a predefined sequence or order?

A-8. Sorting.

Q-9. To sort a data file, what must you tell the sort program?

A-9. What data field or fields to sort on.

Q-10. What are report program generators used for? A-10. To generate programs to print detail and summary reports of data files. Q-11. With early computers, the programmer had to translate instructions into what type of language form?

A-11. Machine. Q-12. When were mnemonic instruction codes and symbolic addresses developed?

A-12. In the early 1950's. Q-13. What led to the development of procedure oriented languages? A-13. The development of mnemonic techniques and macroinstructions. Q-14. What computer language was developed for mathematical work?

A-14. FORTRAN. Q-15. What are two disadvantages of procedure oriented languages? A-15. They require more space in memory and they process data at a slower rate than symbolic languages.

Q-16. What is programming?

A-16. The process of planning the solution to a problem.

Q-17. In programming, how many steps are involved in solving a problem on a computer?

A-17. Four. Q-18. What is required before you can actually start to write or code a program?

A-18. Advance preparation. Q-19. In flowcharting, what method is used to represent different operations, data flow, equipment, and so forth?

A-19. Different shaped symbols. Q-20. What type of flowchart is constructed by the programmer to represent the sequence of operations the computer is to perform to solve a specific problem?

A-20. A programming flowchart.

Q-21. How many tools are used in flowcharting?

A-21. Four.

Q-22. Is there a "best way" to construct a flowchart?

A-22. No, there isn't a way to standardize problem solution.

Q-23. What controls the computer during processing?

A-23. Coded instructions.

Q-24. What is the fundamental element in program preparation?

A-24. The instruction. Q-25. What type of instructions permit addition, subtraction, multiplication, and division?

A-25. Arithmetic. Q-26. Where is specific information about the computer you are to use contained? A-26. In the computer manufacturers or software designers user's manual.

NEETS Q&A

Q-27. How do we refer to errors caused by faulty logic and coding mistakes?

A-27. Bugs.

Q-28. What is the purpose of testing a program? A-28. To determine that all data can be processed correctly and that the output is correct.

Q-29. What is packaged software? A-29. Off-the-shelf programs designed for specific classes of applications. Q-30. What are some of the other features and software available with a word processing software package? A-30. Spelling checkers, mailing list programs, document compilation programs, and communications programs.

Q-31. What software allows you to enter data and then retrieve it in a variety of ways?

A-31. Data management.

Q-32. What are spreadsheets?

A-32. They are tables of rows and columns of numbers.

Q-33. Are all printers capable of handling graphics output?

A-33. No.

SOLID-STATE POWER SUPPLIES

Q1. What are the four basic sections of a power supply?

A1. Transformer, rectifier, filter, regulator.

Q2. What is the purpose of the rectifier section?

A2. To change ac to pulsating dc.

Q3. What is the purpose of the filter section?

A3. To change pulsating dc to pure dc.

Q4. What is the purpose of the regulator section?

A4. To maintain a constant voltage to the load. Q5. What is the name of the simplest type of rectifier which uses one diode?

A5. The half-wave rectifier. Q6. If the output of a half-wave rectifier is 50-volts peak, what is the average voltage?

A6. 15.9 volts. Q7. In addition to stepping up or stepping down the input line voltage, what additional purpose does the transformer serve?

A7. It isolates the chassis from the power line.

Q8. What was the major factor that led to the development of the full-wave rectifier? A8. The fact that the full-wave rectifier uses the full output, both half cycles, of the transformer. Q9. What is the ripple frequency of a full-wave rectifier with an input frequency of 60 Hz?

A9. 120 hertz.

Q10. What is the average voltage (Eavg) Output of a full-wave rectifier with an output of 100 volts peak?

A10. 63.7 volts.

Q11. What is the main disadvantage of a conventional full-wave rectifier?

A11. Peak voltage is half that of the half-wave rectifier. Q12. What main advantage does a bridge rectifier have over a conventional full-wave rectifier? A12. The bridge rectifier can produce twice the voltage with the same size transformer.

Q13. If you increase the value of the capacitor, will the XC increase or decrease? Why?

A13. It will decrease. Capacitance is inversely proportional to:

Q14. What is the most basic type of filter?

A14. The capacitor filter.

Q15. In a capacitor filter, is the capacitor in series or in parallel with the load?

A15. Parallel.

Q16. Is filtering better at a high frequency or at a low frequency?

A16. At a high frequency.

Q17. Does a filter circuit increase or decrease the average output voltage?

A17. A filter circuit increases the average output voltage. Q18. What determines the rate of discharge of the capacitor in a filter circuit?

A18. Value of capacitance and load resistance.

Q19. Does low ripple voltage indicate good or bad filtering?

A19. Good.

Q20. Is a full-wave rectifier output easier to filter than that of a half-wave rectifier?

A20. Yes.

Q21. In an LC choke-input filter, what prevents the rapid charging of the capacitor?

A21. The CEMF of the inductor.

Q22. What is the range of values usually chosen for a choke?

A22. From 1 to 20 henries. Q23. If the impedance of the choke is increased, will the ripple amplitude increase or decrease?

A23. Decrease.

Q24. Why is the use of large value capacitors in filter circuits discouraged?

A24. Expense.

Q25. When is a second RC filter stage used?

A25. When ripple must be held at an absolute minimum.

Q26. What is the most commonly used filter today?

A26. LC capacitor-input filter. Q27. What are the two main disadvantages of an LC capacitor filter?

A27. Cost and size of the inductor.

Q28. Circuits which maintain constant voltage or current outputs are called dc voltage or dc current ___.

A28. Regulators.

Q29. The purpose of a voltage regulator is to provide an output voltage with little or no ___.

A29. Variation.

Q30. The two basic types of voltage regulators are ___ and ___.

A30. Series and shunt.

Q31. When a series voltage regulator is used to control output voltages, any increase in the input voltage results in an increase/a decrease (which one) in the resistance of the regulating device.

A31. An increase. Q32. A shunt-type voltage regulator is connected in serial/parallel (which one) with the load resistance.

A32. In parallel. Q33. In figure 4-37, the voltage drop across RS and R1 determines the amount of base-emitter ____ for Q1.

A33. Bias.

Q34. In figure 4-39, view A, when there is an increase in the input voltage, the forward bias of Q1 increases/decreases (which one).

A34. Increases. Q35. In view B of figure 4-39, when the load current increases and the output voltage momentarily drops, the resistance of Q1 increase/decreases (which one) to compensate.

A35. Increases.

Q36. In figure 4-40, when there is an increase in the load resistance (R L), the resistance of R V increases/decreases (which one) to compensate for the change.

A36. Decreases.

Q37. In figure 4-43 any decrease in the base-emitter forward bias across Q1 results in an increase/a decrease (which one) in the resistance of the transistor.

A37. An increase.

Q38. A half-wave voltage doubler is made up of how many half-wave rectifiers?

A38. Two.

Q39. If a half-wave rectifier is added to a half-wave voltage doubler, the resulting circuit is a voltage ____.

A39. Trippler. Q40. In a full-wave voltage doubler, are the capacitors connected in series or in parallel with the output load?

A40. In parallel. Q41. What is the most important thing to remember when troubleshooting?

A41. Safety precautions. Q42. What is the main reason for grounding the return side of the transformer to the chassis?

A42. To eliminate shock hazard.

Q43. What are two types of checks used in troubleshooting power supplies?

A43. Visual and signal tracing.

SPECIAL AMPLIFIERS

Q-1. How many inputs and outputs are possible with a differential amplifier?

A-1. Two inputs, two outputs. Q-2. What two transistor amplifier configurations are combined in the single-transistor, two-input, single-output difference

NEETS Q&A

amplifier?

A-2. Common emitter (CE) and common base (CB). Q-3. If the two input signals of a difference amplifier are in phase and equal in amplitude, what will the output signal be?

A-3. No output (the signals will "cancel out"). Q-4. If the two input signals to a difference amplifier are equal in amplitude and 180 degrees out of phase, what will the output signal be? A-4. Equal in shape and frequency to each input signal and larger in amplitude by two times than

Q-5. If only one input signal is used with a difference amplifier, what will the output signal be? A-5. Equal in shape and frequency to the input signal; larger in amplitude than the input signal; half as large in amplitude as when two input signals were used that were 180 degrees out of phase. Q-6. If the two input signals to a difference amplifier are equal in amplitude but neither in phase nor 180 degrees out of phase, what will the output signal be?

A-6. A different shape than the input signals but larger in amplitude. In answering Q7 through Q9 use the following information: All input signals are sine waves with a peak-to-peak amplitude of 10 millivolts. The gain of the differential amplifier is 10. Q-7. If the differential amplifier is configured with a single input and a single output, what will the peak-to-peak amplitude of the output signal be?

A-7. 100 millivolts. Q-8. If the differential amplifier is configured with a single input and differential outputs, what will the output signals be? A-8. Each output will be a sine wave with a peak-to-peak amplitude of 100 millivolts. The output signals will be 180 degrees out of phase with each other. Q-9. If the single-input, differential-output, differential amplifier has an output signal taken between the two output terminals, what will the peak-to-peak amplitude of this combined output be?

A-9. 200 millivolts.

In answering Q10 through Q14 use the following information: A differential amplifier is configured with a differential input and a differential output. All input signals are sine waves with a peak-to-peak amplitude of 10 millivolts. The gain of the differential amplifier is 10. Q-10. If the input signals are in phase, what will be the peak-to-peak amplitude of the output signals?

A-10. 0 volts (the input signals will "cancel out"). Q-11. If the input signals are 180 degrees out of phase with each other, what will be the peak-to-peak amplitude of the output signals?

A-11. Each output signal will be 100 millivolts. Q-12. If the input signals are 180 degrees out of phase with each other, what will the phase relationship be between (a) the output signals and (b) the input and output signals? A-12.

a. 180 degrees out of phase with each other. b. Output signal number one will be in phase with input

signal number two; output signal number two will be in phase with input signal number one.

Q-13. If the input signals are 180 degrees out of phase with each other and a combined output is taken between the two output terminals, what will the amplitude of the combined output signal be?

A-13. 200 millivolts. Q-14. If the input signals are 90 degrees out of phase with each other and a combined output is taken between the two output terminals, (a) what will the peak-to-peak amplitude of the combined output signal be, and (b) will the combined output signal be a sine wave? A-14.

a. 100 millivolts. b. No.

Q-15. What are the three requirements for an operational amplifier? A-15. Very high gain, very high input impedance, very low output impedance. Q-16. What is the most commonly used form of the operational amplifier?

A-16. An integrated circuit (chip).

Q-17. Draw the schematic symbol for an operational amplifier.

A-17.

Q-18. Label the parts of the operational amplifier shown in figure 3-12. A-18.

a. Differential amplifier. b. Voltage amplifier. c. Output amplifier.

Q-19. What does the term "closed-loop" mean in the closed-loop configuration of an operational amplifier?

A-19. The use of degenerative (negative) feed-back.

In answering Q20, Q21, and Q23, select the correct response from the choices given in the parentheses. Q-20. In a closed-loop configuration the output signal is determined by (the input signal, the feedback signal, both).

A-20. Both the input signal and the feedback signal. Q-21. In the inverting configuration, the input signal is applied to the (a) (inverting, noninverting) input and the feedback signal is applied to the (b) (inverting, noninverting) input. A-21. a. Inverting. b. Inverting. Q-22. In the inverting configuration, what is the voltage (for all practical purposes) at the inverting input to the operational amplifier if the input signal is a 1-volt, peak-to-peak sine wave?

A-22. 0 volts. Q-23. In the inverting configuration when the noninverting input is grounded, the inverting input is at (signal, virtual) ground.

A-23. Virtual. Q-24. In a circuit such as that shown in figure 3-15, if R1 has a value of 100 ohms and R2 has a value of 1 kilohm and the input signal is at a value of + 5 millivolts, what is the value of the output signal?

A-24. -50 millivolts. Q-25. If the unity-gain point of the operational amplifier used in question 24 is 500 kilohertz, what is the bandwidth of the circuit? A-25. 50 kilohertz (Gain = 10; Gain-Bandwidth Product = 500,000)

50kHz10

)500,000(HzBW ==

Q-26. In a circuit such as that shown in figure 3-16, if R1 has a value of 50 ohms and R2 has a value of 250 ohms and the input signal has a value of +10 millivolts, what is the value of the output signal?

A-26. 60 millivolts.

Q-27. If the open-loop gain of the operational amplifier used in question 26 is 200,000 and the openloop bandwidth is 30 hertz, what is the closed loop bandwidth of the circuit?

A-27. 1 megahertz. Open-loop Gain-Bandwidth Product = Closed-loop Gain-Bandwidth Prod.

Open-loop Gain-Bandwidth Product = 200,000 ´ 30 (Hz)

Open-loop Gain Bandwidth Product = 600,000

Closed-loop Gain Bandwidth Product = 6 ´ Bandwidth

6,000,000 = 6 ‘ Bandwidth

1,000,000 (Hz) = Bandwidth Q-28. What is the difference between a summing amplifier and an adder circuit? A-28. The adder simply adds the input signals together while the summing amplifier multiplies the sum of the input signals by the gain of circuit.

Q-29. Can a summing amplifier have more than two inputs?

A-29. Yes, a summing amplifier can have as many inputs as desired.

Q-30. What is a scaling amplifier? A-30. A summing amplifier that applies a factor to each input signal beforeadding the results.

Q-31. What type of circuit is figure 3-27?

A-31. A scaling amplifier.

Q-32. If: E1 = +2V, and: E2 = +6V, then Eout = ?

A-32.

)3kΩ

30kΩ6V()

5kΩ

30kΩ2V(- Eout

:Solution

72VEout

×++×+=

−=

Q-33. What is the difference in potential between the inverting (-) and noninverting (+) inputs to the operational amplifier when: E1 = +6V, and E2 = +2V A-33. 0 volts. (The two inputs to the operational amplifier are both at 0 volts.) Q-34. What is the difference between a subtractor and a difference amplifier? A-34. The difference amplifier multiplies the difference between the two inputs by the gain of the circuit while the subtractor merely subtracts one input signal from the other.

Q-35. Can a difference amplifier have more than two inputs?

NEETS Q&A

A-35. No.

Q-36. What type of circuit is figure 3-28?

A-36. A difference amplifier.

Q-37. If: E1 = +5V, and: E2 = +11V, then Eout = ?

A-37.

2kΩ

20kΩ5V)](-11V)[( Eout

:Solution

60VEout

×++=

+=

Q-38. What is the difference in potential between the inverting (-) and noninverting (+) inputs to the operational amplifier when: E1 = +2V, and E2 = +4V A-38. 0 volts. (The two inputs to the operational amplifier are both at the same potential.) Q-39. What is the frequency classification of a magnetic amplifier?

A-39. An audio (or low) frequency power amplifier.

Q-40. What is the basic principle of a magnetic amplifier? A-40. A change in inductance in a series LR circuit causes a change in true power. Q-41. If inductance increases in a series LR circuit, what happens to true power?

A-41. It decreases.

Q-42. If the permeability of the core of a coil increases, what happens to (a) inductance and (b) true power in the circuit?

A-42. (a) Inductance increases; (b) true power decreases. Q-43. What happens to the permeability of an iron core as the current increases from the operating point to a large value?

A-43. Permeability decreases. Q-44. If two coils are wound on a single iron core, what will a change in current in one coil cause in the other coil?

A-44. A change in inductance. Q-45. What symbol in figure 3-33 indicates a saturable core connecting two windings?

A-45. Q-46. At what portion of the magnetization curve should a magnetic amplifier be operated?

A-46. The knee of the curve. Q-47. How is the effect of load flux on control flux eliminated in a saturable-core reactor? A-47. Use two load windings whose flux effects cancel in the core of the reactor or use two load windings on two toroidal cores so that load flux always aids control flux in one core and opposes control flux in the other core. Q-48. What is the purpose of the rectifier in a magnetic amplifier?

A-48. The rectifier eliminates hysteresis loss. Q-49. What is used to bias a magnetic amplifier so that the control winding remains free to accept control (input) signals?

A-49. A bias winding and associated circuitry.

Q-50. List two common usages of magnetic amplifiers.

A-50. Servosystems, temperature recorders, or power supplies.

SPECIAL DEVICES

Q1. In a reverse biased PN-junction, which current carriers cause leakage current?

A1. The minority carriers. Q2. The action of a PN-junction during breakdown can be explained by what two theories?

A2. Zener effect and avalanche effect. Q3. Which breakdown theory explains the action that takes place in a heavily doped PN-junction with a reverse bias of less than 5 volts?

A3. Zener effect. Q4. What is the doping level of an avalanche effect diode when compared to the doping level of a Zener-effect diode?

A4. The doping level of an avalanche effect diode is lower. Q5. During avalanche effect breakdown, what limits current flow through the diode?

A5. An external current-limiting resistor. Q6. Why is electron flow with the arrow in the symbol of a Zener diode instead of against the arrow as it is in a normal diode?

A6. Because Zener diodes are operated in the reverse bias mode.

Q7. What is the main difference in construction between normal PN junction diodes and tunnel diodes?

A7. The amount of doping. Q8. What resistance property is found in tunnel diodes but not in normal diodes?

A8. Negative resistance. Q9. When compared to the ordinary diode, the tunnel diode has what type of depletion region?

A9. The tunnel diode has a very narrow depletion region. Q10. In the tunnel diode, the tunneling current is at what level when the forbidden gap of the N-type material is at the same energy level as the empty states of the P-type material?

A10. Minimum.

Q11. The varactor displays what useful electrical property?

A11. Variable capacitance. Q12. When a PN junction is forward biased, what happens to the depletion region?

A12. The depletion region decreases. Q13. When the reverse bias on a varactor is increased, what happens to the effective capacitance?

A13. Capacitance decreases.

Q14. The SCR is primarily used for what function?

A14. The SCR is primarily used for switching power on or off. Q15. When an SCR is forward biased, what is needed to cause it to conduct?

A15. A gate signal.

Q16. What is the only way to cause an SCR to stop conducting? A16. The forward bias must be reduced below the minimum conduction level.

Q17. The TRIAC is similar in operation to what device?

A17. SCR. Q18. When used for ac current control, during which alternation of the ac cycle does the TRIAC control current flow?

A18. During both alternations. Q19. What type of bias is required to cause an LED to produce light?

A19. Forward bias. Q20. When compared to incandescent lamps, what is the power requirement of an LED?

A20. Very low. Q21. In a common anode, seven-segment LED display, an individual LED will light if a negative voltage is applied to what element?

A21. The cathode. Q22. What is the resistance level of a photodiode in total darkness?

A22. Very high. Q23. What type of bias is required for proper operation of a photodiode?

A23. Reverse bias. Q24. What is a typical light-to-dark resistance ratio for a photocell?

A24. 1:1000. Q25. What semiconductor device produces electrical energy when exposed to light?

A25. Photovoltaic cell.

Q26. The UJT has how many PN junctions?

A26. One. Q27. The area between base 1 and base 2 in a UJT acts as what type of common circuit component?

A27. Variable resistor. Q28. The sequential rise in voltage between the two bases of the UJT is called what?

A28. A voltage gradient.

Q29. What is the normal current path for a UJT?

A29. From base 1 to the emitter. Q30. What is one of the primary advantages of the FET when compared to the bipolar transistor?

A30. High input impedance.

Q31. The FET and the vacuum tube have what in common?

A31. Voltage controls conduction. Q32. The base of a transistor serves a purpose similar to what element of the FET?

A32. Gate.

Q33. What are the two types of JFET?

A33. N-channel and P-channel. Q34. The source and drain of an N-channel JFET are made of what type of material?

NEETS Q&A

A34. N-type material.

Q35. What is the key to FET operation?

A35. Effective cross-sectional area of the channel.

Q36. What is the normal current path in an N-channel JFET?

A36. From source to drain. Q37. Applying a reverse bias to the gate of an FET has what effect?

A37. Source-to-drain resistance increases. Q38. The input and output signals of a JFET amplifier have what phase relationship?

A38. They are 180 degrees out of phase. Q39. When compared to the JFET, what is the input impedance of the MOSFET?

A39. The MOSFET has a higher input impedance.

Q40. What are the four elements of the MOSFET?

A40. Gate, source, drain, and substrate. Q41. The substrate of an N-channel MOSFET is made of what material?

A41. P-type material. Q42. In a MOSFET, which element is insulated from the channel material?

A42. The gate terminal. Q43. What type of MOSFET can be independently controlled by two separate signals?

A43. The dual-gate MOSFET. Q44. What is the purpose of the spring or wire around the leads of a new MOSFET?

A44. To prevent damage from static electricity.

SPECIAL LOGIC CIRCUITS

Q1. What is the sign of operation for the X-OR gate?

A1. XOR Q2. What will be the output of an X-OR gate when both inputs are HIGH?

A2. Low (0). Q3. A two-input X-OR gate will produce a HIGH output when the inputs are at what logic levels? A3. One or the other of the inputs must be HIGH, but not both at the same time. Q4. What type of gate is represented by the output Boolean expression R T Å ?

A4. Exclusive NOR (X-NOR). Q5. What will be the output of an X-NOR gate when both inputs are LOW?

A5. HIGH. Q6. What advantage does a half adder have over a quarter adder?

A6. The half adder generates a carry.

Q7. An X-OR gate may be used as what type of adder?

A7. Quarter adder. Q8. What will be the output of a half adder when both inputs are 1s?

A8. Sum equals 0 with a carry of 1. Q9. What type of adder is used to handle a carry from a previous circuit?

A9. Full adder. Q10. How many full adders are required to add four-digit numbers?

A10. Four. Q11. With the inputs shown below, what will be the output of S1, S2, and C2?

A11. S1 = 1, S2 = 0 and C2 = 1.

Q12. What is the output of C1?

A12. C1 = 0. Q13. What type of logic gates are added to a parallel adder to enable it to subtract?

A13. X-OR gates. Q14. How many of these gates would be needed to add a four-digit number?

A14. Four.

Q15. In the add mode, what does the output of C2 indicate?

A15. MSD of the sum. Q16. In the subtract mode, a 1 at C0 performs what portion of the R’s complement?

A16. Add 1 portion.

Q17. In the subtract mode, which portion of the problem is complemented?

A17. Subtrahend.

Q18. What are R-S FFs used for?

A18. Storing information. Q19. How many R-S FFs are required to store the number 1001012?

A19. Six. Q20. For an R-S FF to change output conditions, the inputs must be in what states?

A20. 1 and 0, or opposite states.

Q21. How may R-S FFs be constructed?

A21. By cross-coupling NAND or OR gates.

Q22. How many inputs does a T FF have?

A22. One.

Q23. What is the purpose of using T FFs?

A23. To divide the input by 2.

Q24. What are the inputs to a D FF?

A24. Clock and data.

Q25. How long is data delayed by a D FF?

A25. Up to one clock pulse. Q26. What condition must occur to have a change in the output of a D FF?

A26. A positive-going clock pulse.

Q27. What type of FF can be used as an R-S, a T, or a D FF?

A27. J-K flip-flop. Q28. What will be the output of Q if J is HIGH, PS and CLR are HIGH, and the clock is going negative?

A28. Set, or HIGH (1). Q29. Assume that K goes HIGH and J goes LOW; when will the FF reset?

A29. When the clock pulse goes LOW. Q30. What logic levels must exist for the FF to be toggled by the clock?

A30. Both J and K must be HIGH.

Q31. What two inputs to a J-K FF will override the other inputs?

A31. Clear (CLR) and preset (PS or PR).

Q32. How is the J-K FF affected if PS and CLR are both LOW?

A32. The flip-flop is jammed.

Q33. What is a clock with regard to digital equipment?

A33. A timing signal.

Q34. What is the simplest type of clock circuit?

A34. An astable or free-running multivibrator. Q35. What is needed to use a monostable or one-shot multivibrator for a clock circuit?

A35. Triggers. Q36. What type of clock is used when more than one operation is to be completed during one clock cycle?

A36. A multiphase clock.

Q37. What is the modulus of a five-stage binary counter?

A37. 32. Q38. An asynchronous counter is also called a ___________ counter.

A38. Ripple. Q39. J-K FFs used in counters are wired to perform what function?

A39. Toggle.

Q40. What type of counter has clock pulses applied to all FFs?

A40. Synchronous. Q41. In figure 3-24, view A, what logic element enables FF3 to toggle with the clock?

A41. The AND gate. Q42. What is the largest count that can be indicated by a four-stage counter?

A42. 11112, or 1510.

Q43. How many stages are required for a decade counter?

A43. Four. Q44. In figure 3-25, which two FFs must be HIGH to reset the counter?

A44. FFs 2 and 4.

Q45. In figure 3-26, view A, which AND gate causes FF3 to set?

A45. Two.

Q46. Which AND gate causes FF3 to reset?

NEETS Q&A

A46. Three.

Q47. What causes the specified condition to shift position?

A47. The input, or clock pulse. Q48. If the specified state is OFF, how many FFs may be off at one time?

A48. One.

Q49. How many FFs are required to count down from 1510?

A49. Four.

Q50. What signal causes FF2 to toggle?

A50. Q output of FF 1 going LOW.

Q51. How many stages are required to store a 16-bit word?

A51. 16. Q52. Simultaneous transfer of data may be accomplished with what type of register?

A52. Parallel.

Q53. How are erroneous transfers of data prevented?

A53. By clearing the register. Q54. Serial-to-parallel and parallel-to-serial conversions are accomplished by what type of circuit?

A54. Shift register.

Q55. What type of data transfer requires the most time?

A55. Serial.

Q56. What is the main disadvantage of parallel transfer?

A56. Requires more circuitry.

Q57. How many FFs would be required for an 8-bit shift register?

A57. Eight. Q58. How many clock pulses are required to output a 4-bit number in serial form?

A58. Four. Q59. Two shifts to the left are equal to increasing the magnitude of a number by how much?

A59. 22, or four times. Q60. To increase the magnitude of a number by 23, you must shift the number how many times and in what direction?

A60. Three to the left.

Q61. What are RTL, DTL, and TTL examples of?

A61. Logic families.

Q62. What type of logic family uses diodes in the input?

A62. DTL (diode transistor logic). Q63. What is the most common type of integrated circuit packaging found in military equipment?

A63. DIPs (dual inline packages). Q64. Circuits that can be interconnected without additional circuitry are known as ____________ circuits.

A64. Compatible.

SPECIAL-PURPOSE TUBES

Q1. What is the major difference in grid construction between power pentodes and conventional pentodes? A1. Conventional pentodes have a staggered grid arrangement, while power pentodes have a shielded grid arrangement. Q2. Beam-forming tubes and power tubes are similar except that power pentodes lack what element?

A2. Beam-forming plates. Q3. What effect does the shielding of the screen grid by the control grid have on plate current in beam-forming tetrodes? A3. By increasing the number of electrons that reach the plate, plate current is increased. Q4. What effect does a large negative input signal applied to a variable-mu tube have on

a. conduction through the control grid, and

b. gain of the tube? A4.

a. A large negative voltage causes conduction to occur only at the center of the grid.

b. Decreases gain. Q5. Identify the type of electron tube(s) that would be most suitable for the following applications.

a. Power amplifier

b. Voltage amplifier with small signal inputs

c. Low distortion amplifiers for use with large signal inputs A5.

a. Power pentode or beam-forming tetrode. b. Conventional tube.

c. Variable-mu tube.

Q6. What effect does transit time have on a conventional triode operated at uhf frequencies?

A6. It causes the control grid to short to the cathode.

Q7. How do uhf tubes counter the effects of transit time?

A7. By reducing the spacing between tube elements. Q8. Why can acorn and doorknob tubes NOT handle large amounts of power? A8. The close spacing of tube elements allows for the ready formation of arcs or short circuits. Q9. What type of uhf tube was developed to handle large amounts of power?

A9. Planar Q10. What are two advantages that gas-filled tubes have over conventional electron tubes? A10.

a. They can carry more current. b. They maintain a constant IR drop across the tube.

Q11. Once ionization has occurred in a thyratron, what control does the control grid have over the tube’s operation?

A11. None. Q12. What precautions should be exercised when using mercury-vapor thyratrons? A12. The filament’s voltage should be applied to the tube at least 30 seconds before attempting to operate the tube. Q13. Cold-cathode tubes can be used as voltage regulators because of what characteristic? A13. They have the ability to maintain a constant voltage drop across the tube despite changes in current flow.

Q14. What is the unique ability of the CRT?

A14. To visually display electronic signals.

Q15. What are the three main parts of CRT? A15.

a. Electron gun. b. Deflection system

Q16. What term is used for the ability of a spot on a CRT screen to continue to glow after the electron bean has struck it and moved away?

A16. Persistence. Q17. The electron beam in a CRT is made to sweep from left to right across the screen. What tube element causes this sweeping motion?

A17. The horizontal-deflection plate. Q18. In applications where electronic waveforms are displayed on a CRT screen, the input signal is normally applied to what CRT element?

A18. The vertical-deflection plate.

SYNCHROS

Q-1. What is the name given to a variety of rotary electromechanical, position sensing devices?

A-1. The synchro.

Q-2. What is the primary purpose of a synchro system? A-2. Precise and rapid transmission of data between equipment and stations.

Q-3. Name the two general classifications of synchro systems.

A-3. Torque and control. Q-4. What is the difference between a torque synchro and a control synchro? A-4. A torque synchro is used for light loads and a control synchro is used in systems desired to move heavy loads. Q-5. Using table 1-1, name two synchros that provide a mechanical output. A-5. The torque receiver (TR) and the torque differential receiver (TDR). Q-6. What does the code 26V-11TX4D mean on a synchro nameplate? A-6. It is the third modification of a 26-volt 400-hertz (torque) synchro transmitter whose body diameter is between 1.01 and 1.10 inches. Q-7. Which of the two synchro designation codes is indicated by 5DG on a synchro nameplate?

A-7. The Navy prestandard designation code. Q8. On the synchro schematic symbol, what indicates the angular displacement of the rotor?

A-8. The position of the arrow.

Q-9. What are the two major components of a synchro?

A-9. The rotor and the stator. Q-10. Which of the two main types of rotors can have either a single winding or three Y-connected windings?

NEETS Q&A

A-10. The drum or wound rotor.

Q-11. How does the stator receive its voltage?

A-11. By the magnetic coupling from the rotor. Q-12. Where are the external connections made on standard synchros?

A-12. At the terminal board. Q-13. What major factors determine the load capacity of a torque-synchro transmitter? A-13. The number and type of synchro receivers, the mechanical loads on these receivers and the operating temperatures of both the transmitter and receivers.

Q-14. Define the term "torque."

A-14. A measure of how much load a machine can turn. Q-15. What unit of measurement refers to the torque of a synchro transmitter?

A-15. Ounce-inches. Q-16. What type of equipment normally uses 26-volt 400-hertz synchros?

A-16. Aircraft. Q-17. When will a synchro generate more heat than it is designed to handle?

A-17. When it is overloaded.

Q-18. How do synchros differ from conventional transformers? A-18. Synchros have one primary winding that can be turned through 360º and three secondary windings spaced 120º apart.

Q-19. Describe the zero-position of a synchro transmitter. A-19. The transmitter is in its zero-position when the rotor is aligned with the S2 stator winding.

Q-20. When is the maximum voltage induced into a stator coil?

A-20. When the rotor coil is aligned with the stator coil. Q-21. What three factors determine the amplitude of the voltage induced into a stator winding? A-21. The amplitude of the primary voltage, the turns ratio, and the angular displacement between the rotor and the stator winding. Q-22. What is the physical difference between a synchro transmitter and a synchro receiver? A-22. A synchro receiver uses some form of damping to retard excessive oscillations or spinning. Q-23. What method is used to prevent oscillations in large synchro units?

A-23. Mechanical damping. Q-24. What two components make up a simple synchro transmission system?

A-24. A synchro transmitter and a synchro receiver. Q-25. What leads in a simple synchro system are connected to the ac power line?

A-25. The rotor leads.

Q-26. What is the relationship between the transmitter and receiver stator voltages when their rotors are in correspondence?

A-26. The voltages are equal and oppose each other. Q-27. What is the name given to the angle through which a transmitters rotor is mechanically rotated?

A-27. Signal. Q-28. What two receiver leads are reversed to reverse the rotor's direction of rotation?

A-28. 1 and S3. Q-29. What is the most likely problem if the transmitter shaft reads 0º when the receiver shaft indicates 180º? A-29. The rotor leads on either the transmitter or the receiver are reversed. Q-30. What is the purpose of using differential synchros instead of regular synchros? A-30. Differential synchros can handle more signals than regular synchros and also perform addition and subtraction functions.

Q-31. What are the two types of differential synchros?

A-31. The TDX and the TDR. Q-32. Other than their physical differences, what is the major difference between a TDX and a TDR? A-32. Their application: a TDX has one electrical and one mechanical input with an electrical output. Q-33. What determines whether a differential synchro adds or subtracts? A-33. The way the differential synchro is connected in a system is the deciding factor on whether the unit adds or subtracts its inputs. Q-34. In a TDX system when does the TR rotor follow the TX rotor exactly?

A-34. When the TDX rotor is on 0º.

Q-35. What is the angular position of a TX rotor when it is

pointing toward the S1 winding? (Hint. Remember synchros are labeled counter clockwise from 0º.)

A-35. 240º. Q-36. In a TDX system with standard synchro connections, the TX rotor is at 120º and the TDX rotor is at 40º. What position will the TR indicate?

A-36. 80º. Q-37. What connections in a TDX system are reversed to set up the system for addition? A-37. The S1 and S3 leads are reversed between the TX and the TDX, and the R1 and R3 leads are reversed between the TDX rotor and the TR. Q-38. What connections in a TDR system are reversed to set up the system for addition? A-38. The R1 and R3 leads between the TDR rotor and the TX to which it is connected. Q-39. In a TDR system connected for addition in what direction will the TDR rotor field turn when the TX rotor to which it is connected turns counterclockwise?

A-39. Clockwise. Q-40. What type of synchro is used in systems requiring large amounts of power and a high degree of accuracy?

A-40. A control synchro.

Q-41. What are the three types of control synchros?

A-41. CX, CT, and CDX.

Q-42. How do the CX and CDX differ from the TX and TDX?

A-42. The CX and CDX have higher impedance windings. Q-43. What three things prevent a CT rotor from turning when voltages are applied to its stator windings? A-43. The rotor is specially wound, it is never connected to an ac supply, and its output is always applied to a high-impedance load. Q-44. When a CT is on electrical zero, what is the relationship between its rotor and the S2 winding?

A-44. They are perpendicular to each other. Q-45. What is the amplitude and voltage induced into the rotor when the CX is turned 90º while the CT remains on electrical zero? A-45. The voltage is maximum and in phase with the ac excitation voltage to the CX.

Q-46. What is the name given to the electrical output of a CT?

A-46. Error signal. Q-47. In a control synchro system, when is the output of the CT reduced to zero?

A-47. When the CX and CT rotors are in correspondence.

Q-48. What is the purpose of the synchro capacitor? A-48. To improve overall synchro system accuracy by reducing stator currents. Q-49. What type of synchros usually require the use of synchro capacitors?

A-49. TDXs, CDXs, and Cts.

Q-50. What type of current is eliminated by synchro capacitors?

A-50. Magnetizing current.

Q-51. How are synchro capacitors connected in a circuit?

A-51. They are delta-connected across the stator windings. Q-52. Why are synchro capacitors placed physically close to differentials transmitters and CTs? A-52. To keep the connections as short as possible in order to maintain system. Q-53. What is the name given to the synchro system that transmits data at two different speeds?

A-53. A dual or double-speed synchro system. Q-54. What is the main reason for using a multispeed synchro system instead of a single-speed synchro system? A-54. Greater accuracy without the loss of self-synchronous operation. Q-55. In a dual-speed synchro system what determines the two specific speeds at which the data will be transmitted?

A-55. The gear ratio between the two transmitters. Q-56. What type of synchro system is used to transmit very large quantities?

A-56. A tri-speed synchro system. Q-57. What is the disadvantage of using a double receiver instead of two individual receivers? A-57. If one of the receivers goes bad the entire unit must be replaced.

Q-58. What is the purpose of "stickoff voltage"?

A-58. It is used in synchro systems to prevent false synchronizations. Q-59. What is the reference point for alignment of all synchro units?

A-60. The voltmeter method.

Q-60. What is the most accurate method of zeroing a synchro?

NEETS Q&A

A-59. Electrical zero.

Q-61. What is the purpose of the coarse setting of a synchro?

A-61. A61.It ensures the synchro is on 0º, not 180º.

Q-62. When is a synchro receiver (TR) properly zeroed? A-62. A TR is zeroed when electrical zero voltages exist across its stator windings at the same time its rotor is on zero or on its mechanical reference position. Q-63. What should a voltmeter read when a TX is set on coarse zero?

A-63. Approximately 37 volts. Q-64. What precaution should you take when you use 115 volts to zero a differential?

A-64. Never leave the circuit energized for more than 2 minutes. Q-65. Why should a synchro be rechecked for zero after it is clamped down? A-65. To ensure that it did not move off zero while it was being clamped. Q-66. What is the output voltage of a CT when it is set on electrical zero?

A-66. Zero or minimum voltage. Q-67. When you zero a multispeed synchro system which synchro should you zero first?

A-67. The coarse synchro. Q-68. What method of zeroing a synchro is perhaps the fastest but NOT necessarily the most accurate?

A-68. The electrical lock method. Q-69. What restrictions are placed on the use of the electrical lock method? A-69. It can be used only if the leads of the synchro are accessible and the rotor is free to turn. Q-70. When you zero a synchro with a synchro tester, what is indicated by a jump in the synchro tester's dial when the S1 and S3 leads are momentarily shorted?

A-70. The synchro under test is not on electrical zero. Q-71. What should you do with a synchro that has a bad set of bearings?

A-71. Replace it. Q-72. Name two types of trouble you would expect to find in a newly installed synchro system.

A-72. Improper wiring and misalignment. Q-73. What type of indicator is usually placed in the stator circuit of a torque synchro system?

A-73. An overload indicator. Q-74. What is the most probable cause of trouble in a synchro system that has all of its receivers reading incorrectly?

A-74. The transmitter or main bus.

Q-75. If an ac voltmeter is connected between the S2 and S3 windings on a TX, at what two rotor positions should the voltmeter read maximum voltage?

A-75. 150º and 330º Q-76. What precaution should you take when substituting a synchro tester in a circuit for a transmitter?

A-76. Use only one receiver so as not to overload the tester.

TEST EQUIPMENT ADMINISTRATION AND USE

Q-1. What system is currently used by all branches of the military to identify test equipment?

A-1. Joint Electronics Type Designation System (JETDS).

Q-2. Name the two classes of test equipment. A-2. General-purpose electronic test equipment (GPETE) and special-purpose electronic test equipment (SPETE). Q-3. What test equipment is designed to generate, modify, or measure a range of parameters of electronic functions of a specific nature required to test a single system or equipment?

A-3. Special-purpose electronic test equipment.

Q-4. Name the two basic elements of the SCLSIS program.

A-4. Validation and updating. Q-5. What calibration label is used when actual measurement values must be known to use the test equipment?

A-5. CALIBRATED—REFER TO REPORT. Q-6. An instrument that must be calibrated in place requires what type of calibration label?

A-6. SPECIAL CALIBRATION label. Q-7. Responsibility for repair and maintenance of test equipment generally rests with what group of personnel?

A-7. Maintenance personnel.

Q-8. What Navy office oversees the MEASURE program?

A-8. The Chief of Naval Operations.

Q-9. What are the two main categories of maintenance?

A-9. Preventive and corrective maintenance. Q-10. What type of maintenance involves isolating equipment troubles and replacing defective parts?

A-10. Corrective maintenance. Q-11. Which quantity (voltage or current) determines the intensity of an electrical shock?

A-11. Current. Q-12. What tool is used to de-energize capacitors in a circuit that has been disconnected from its power source?

A-12. Shorting probe. Q-13. On what range should you set the voltmeter prior to taking a voltage measurement?

A-13. Highest. Q-14. When taking a voltage measurement, which lead of the voltmeter should you connect to the circuit first?

A-14. Ground. Q-15. Is an ammeter connected in series or in parallel with the circuit under test?

A-15. In series. Q-16. What must be done to a circuit before you can use an ohmmeter for testing?

A-16. It must be de-energized. Q-17. What is the term used to refer to the losses which can be traced to the dielectric of a capacitor?

A-17. Power losses. Q-18. What effect does an increase in capacitance have on a capacitor’s opposition to current flow?

A-18. Opposition to current flow decreases. Q-19. When a bridge is used to measure resistance, what is the value of Rx if R1 equals 80 ohms, R2 equals 120 ohms, and R3 equals 280 ohms?

A-19. 420 ohms. Q-20. When an unknown capacitance is tested with a bridge, what is the value of Cx if R1 equals 70 ohms, R2 equals 150 ohms, and Cs equals 550 microfarads?

A-20. 256 microfarads.

THE OSCILLOSCOPE AND SPECTRUM ANALYZER

Q-1. What element controls the number of electrons striking the screen?

A-1. Control grid.

Q-2. What element is controlled to focus the beam?

A-2. The first anode. Q-3. Why are the electrostatic fields between the electron gun elements called lenses? A-3. Because they bend electron streams in much the same manner that optical lenses bend light rays.

Q-4. What is the function of the second anode?

A-4. It accelerates the electrons emerging from the first anode. Q-5. What effect do longer deflection plates have on the electron beam?

A-5. A greater deflection angle. Q-6. What effect does closer spacing of plates have on the electron beam?

A-6. A greater deflection angle. Q-7. Is the deflection angle greater with higher or lower potential on the plates?

A-7. Higher potential. Q-8. Is the deflection angle greater when the beam is moving faster or slower?

A-8. Slower beam.

Q-9. Waveforms are described in terms of what two functions?

A-9. Amplitude and time. Q-10. The vertical-deflection plates are used to reproduce what function?

A-10. Amplitude. Q-11. The horizontal-deflection plates are used to produce what function?

A-11. Time and/or frequency relationships.

Q-12. Why are the ends of the deflection plates bent outward?

A-12. To permit wide-angle deflection of the beam.

NEETS Q&A

Q-13. What term is used to describe the reciprocal of deflection sensitivity of a scope?

A-13. Deflection factor.

Q-14. List the circuits that all oscilloscopes have in common. A-14. A CRT, a group of control circuits, power supply, sweep circuitry, and deflection circuitry. Q-15. When you select the time base to display a signal, should the time base be the same, higher, or lower than the input signal?

A-15. Lower.

Q-16. Oscilloscopes are used to measure what quantities?

A-16. Amplitude, phase, time, and frequency. Q-17. Scopes that produce two channels on a single CRT with a single beam are referred to as what types of scopes?

A-17. Dual-trace oscilloscopes.

Q-18. The first converter is also known by what other name?

A-18. Front end.

TRANSFORMERS

Q1. What is meant is "transformer action"? A1. The transfer of energy from one circuit to another circuit by electromagnetic induction.

Q2. What are the three basic parts of a transformer?

A2. Primary winding; secondary winding; core.

Q3. What are three materials commonly used as the core of a transformer? A3. Air; soft iron; steel.

Q4. What are the two main types of cores used in transformers?

A4. Hollow-core type; shell-core type.

Q5. Which transformer windings are connected to an ac voltage and to a load, respectively? A5. Primary to source; secondary to load.

Q6. A transformer designed for high-voltage applications differs in construction in what way from a transformer designed for low-voltage applications? A6. Additional insulation is provided between the layers of windings in the high-voltage transformer. Q7. Identify the schematic symbols of transformers by labeling them in the blanks provided.

A7. a. air-core transformer b. iron-core transformer c. iron-core center tapped transformer Q8. What is meant by a "no-load condition" in a transformer circuit? A8. A voltage is applied to the primary, but no load is connected to the secondary.

Q9. What is meant by "exciting current" in a transformer? A9. Exciting current is the current that flows in the primary of a transformer with the secondary open (no load attached). Q10. What is the name of the emf generated in the primary that opposes the flow of current in the primary? A10. Self-induced or counter emf

Q11. What causes a voltage to be developed across the secondary winding of a transformer? A11. The magnetic lines generated by the current in the primary cut the secondary windings and induce a voltage into them. Q12. What is the phase relationship between the voltage induced in the secondary of an unlike-wound transformer and the counter emf of the primary winding? A12. In phase. Remember, the emf of the primary is 180 degrees out of phase with the applied voltage. The induced voltage of the secondary of an unlike-wound transformer is also 180 degrees out of phase with the primary voltage. Q13. Draw dots on the below symbol to indicate the phasing of the transformer.

A13.

Q14. What is "leakage flux?" A14. Lines of flux generated by one winding which do not link the other winding. Q15. What effect does flux leakage in a transformer have on the coefficient of coupling (K) in the transformer? A15. it causes K to be less than unity (I).

Q16. Does 1:5 indicate a step-up or step-down transformer?

A16. Step up.

Q17. A transformer has 500 turns on the primary and 1500 turns on the secondary. If 45 volts are applied to the primary, what is the voltage developed across the secondary? (Assume no losses)

A17.

135Vturns500

turns1500 45V

N

NE E

or N

N

E

E

P

SPS

P

S

P

S

=×

==

=

Q18. A transformer has a turn’s ratio of 7:1. If 5 volts is developed across the secondary, what is the voltage applied to the primary? (Note: ES is given, what is EP?)

A18.

35Vturn 1

V 5 turns 7

N

NE E

or N

N

E

E

S

PSP

S

P

S

P

=×

==

=

Q19. A transformer has 60 volts applied to its primary and 420 volts appearing across its secondary. If there are 800 turns on the primary, what is the number of turns in the secondary?

A19.

turns5600 V60

turns800 V420

E

NE N

or N

N

E

E

P

PSS

S

P

S

P

=×

==

=

Q20. A transformer with a turn’s ratio of 1:# has what current ratio?

A20. ratio current 1:33

1

I

I

N

N

P

S

S

P ===

(Turns ratio and current ratio have an inverse relationship.) Q21. A transformer has a turn’s ratio of 5:1 and a current of 5 amperes flowing in the secondary. What is the current flowing in the primary? (Assume no losses)

A21.

A 1turns 5

A 5 turn 1

N

IN I

or I

I

N

N

P

SSP

P

S

S

P

=×

==

=

Q22. What is the mathematical relationship between the power in the primary (PP) and power in the secondary (PS) of a transformer? A22. PS = PP - PL

Q23. Name the three power losses in a transformer.

A23. Copper-loss, eddy-current loss, and hysteresis loss.

Q24. The input power to a transformer is 1,000 watts and the output power is 500 watts. What is the efficiency of the transformer, expressed as a percentage?

A24.

50%1000.51001000W

500W

100Pin

Pout Eff(in%)

=×=×

×=

Q25. Why a transformer designed for 400 hertz operation should not be used for 60 hertz operation? A25. The inductive reactance at 60hertz would be too low. The resulting excessive current would probably damage the transformer. Q26. List five different types of transformers according to their applications. A26. a. Power Transformer b. Autotransformer c. Impedance-matching transformer d. audio-frequency transformer e. radio-frequency transformer

Q27. The leads to the primary and the high-voltage secondary

NEETS Q&A

windings of a power transformer usually are of what color?

A27. Primary leads-black; secondary leads red.

Q28. What is the cause of most accidents?

A28. Carelessness.

Q29. Before working on electrical equipment containing capacitors, what should you do to the capacitors? A29. Discharge them by shorting them to ground.

Q30. When working on electrical equipment, why should you use only one hand? A30. To minimize the probability of providing a path for current through your body.

TRANSISTORS

Q1. What is the name given to the semiconductor device that has three or more elements?

A1. Transistor

Q2. What electronic function made the transistor famous?

A2. Amplification. Q3. In which direction does the arrow point on an NPN transistor?

A3. Outward.

Q4. What was the name of the very first transistor?

A4. Point-contact. Q5. What is one of the most important parts of any transistor manufacturing process?

A5. Quality control. Q6. To properly bias an NPN transistor, what polarity voltage is applied to the collector, and what is its relationship to the base voltage?

A6. Positive, more positive. Q7. Why is conduction through the forward-biased junction of an NPN transistor primarily in one direction, namely from the emitter to base? A7. Because the N material on one side of the forward-biased junction is more heavily doped than the P-material. Q8. In the NPN transistor, what section is made very thin compared with the other two sections?

A8. The P or base section. Q9. What percentage of current in an NPN transistor reaches the collector?

A9. 98 percent.

Q10. What are the majority current carriers in a PNP transistor?

A10. Holes. Q11. What is the relationship between the polarity of the voltage applied to the PNP transistor and that applied to the NPN transistor? A11. The polarity of voltage applied to the PNP transistor is opposite of that applied to the NPN

Q12. What is the letter designation for base current?

A12. I B.

Q13. Name the two current loops in a transistor.

A13. The base current loop and the collector current loop. Q14. What is the name of the device that provides an increase in current, voltage, or power of a signal without appreciably altering the original signal?

A14. Amplifier. Q15. Besides eliminating the emitter-base battery, what other advantages can different biasing methods offer? A15. Compensation for slight variations in transistor characteristics and changes in transistor conduction because of temperature variations. Q16. In the basic transistor amplifier discussed earlier, what is the relationship between the polarity of the input and output signals? A16. The signals are opposite in polarity or 180 degrees out of phase with each other. Q17. What is the primary difference between the NPN and PNP amplifiers?

A17. The polarity of the source voltage.

Q18. Which biasing method is the most unstable?

A18. Base current bias or fixed bias. Q19. What type of bias is used where only moderate changes in ambient temperature are expected?

A19. Self-bias.

Q20. When is degeneration tolerable in an amplifier?

A20. When it is necessary to prevent amplitude distortion.

Q21. What is the most widely used combination-bias system?

A21. The voltage-divider type. Q22. What amplifier class of operation allows collector current to flow during the complete cycle of the input?

A22. Class A. Q23. What is the name of the term used to describe the condition in a transistor when the emitter-base junction has zero bias or is reverse biased and there is no collector current?

A23. Cutoff. Q24. What two primary items determine the class of operation of an amplifier?

A24. The amount of bias and the amplitude of the input signal. Q25. What amplifier class of operation is the most inefficient but has the least distortion?

A25. Class A.

Q26. What are the three transistor configurations? A26. Common emitter (CE), common base (CB), and common collector (CC). Q27. Which transistor configuration provides a phase reversal between the input and output signals?

A27. Common emitter.

Q28. What is the input current in the common-emitter circuit?

A28. Base current (IB).

Q29. What is the current gain in a common-base circuit called?

A29. Alpha (α). Q30. Which transistor configuration has a current gain of less than 1?

A30. Common base.

Q31. What is the output current in the common-collector circuit?

A31. IE. Q32. Which transistor configuration has the highest input resistance?

A32. Common collector.

Q33. What is the formula for GAMMA (γ)?

A33.

BIE

Iγ =

Q34. List three items of information normally included in the general description section of a specification sheet for a transistor. A34. The kind of transistor, the transistor's common applications, and mechanical data. Q35. What does the number "2" (before the letter "N") indicate in the JAN marking scheme? A35. The number of junctions in the device, which in this case indicates a transistor.

Q36. What is the greatest danger to a transistor?

A36. Heat. Q37. What method for checking transistors is cumbersome when more than one transistor is bad in a circuit?

A37. The substitution method. Q38. What safety precaution must be taken before replacing a transistor?

A38. The power must be removed from the circuit. Q39. How is the collector lead identified on an oval-shaped transistor? A39. By the wide space between the collector lead and the other two leads (emitter and base). Q40. What are two transistor tests that can be done with an ohmmeter?

A40. Gain and junction resistance. Q41. When you are testing the gain of an audio-frequency transistor with an ohmmeter, what is indicated by a 10-to-1 resistance ratio?

A41. Normal gain. Q42. When you are using an ohmmeter to test a transistor for leakage, what is indicated by a low, but not shorted, reverse resistance reading?

A42. A leaking transistor

TUNED CIRCUITS

Q-1. What is the relationship between frequency and the values of (a) XL, (b) XC, and (c) R? A-1. a. XL varies directly with frequency. XL = 2 πfL b. XC varies inversely with frequency.

NEETS Q&A

fC2

1XC

π=

c. Frequency has no affect on resistance. Q-2. In an a.c. circuit that contains both an inductor and a capacitor, what term is used for the difference between the individual reactances?

A-2. Resultant reactance.

Q-3. State the formula for resonant frequency.

A-3. LC

0.159 or

LC2

1fr

π=

Q-4. If the inductor and capacitor values are increased, what happens to the resonant frequency?

A-4. Decreases. Q-5. In an "ideal" resonant circuit, what is the relationship between impedance and current?

A-5. Impedance low Current high. Q-6. In a series-RLC circuit, what is the condition of the circuit if there is high impedance, low current, and low reactance voltages?

A-6. Nonresonant (circuit is either above or below resonance). Q-7. When the capacitor is completely discharged, where is the energy of the tank circuit stored?

A-7. Inductor magnetic field. Q-8. When the magnetic field of the inductor is completely collapsed, where is the energy of the tank circuit stored?

A-8. Capacitor. Q-9. What is the term for the number of times per second that tank circuit energy is either stored in the inductor or capacitor?

A-9. Natural frequency or resonant frequency (f r). Q-10. In a parallel-resonant circuit, what is the relationship between impedance and current?

A-10. Maximum impedance, minimum current.

Q-11. When is line current minimum in a parallel-LC circuit?

A-11. At the resonant frequency. Q-12. What is the relationship of the coil to the resistance of a circuit with high "Q"?

A-12. ( )R low XL, highR

XLQ

=

Q-13. What is the band of frequencies called that is included between the two points at which current falls to 70 percent of its maximum value in a resonant circuit?

A-13. Bandwidth of the circuit. Q-14. What is the device called that will separate alternating current from direct current, or that will separate alternating current of one frequency from other alternating currents of different frequencies?

A-14. A filter.

Q-15. What are the four general types of filters? A-15. a. Low-pass. b. High-pass c. Bandpass d. Band-reject.. Q-16. What is the filter called in which the low frequencies do not produce a useful voltage? A-16. High-pass filter, low-frequency discriminator, or low-frequency attenuator. Q-17. What is the filter called that passes low frequencies but rejects or attenuates high frequencies? A-17. Low-pass filter, high-frequency discriminator or high-frequency attenuator. Q-18. How does a capacitor and an inductor react to (a) low frequency and (b) high frequency? A-18. At low-frequency, a capacitor acts as an open and an inductor acts as a short. At high-frequency, a capacitor acts as a short and an inductor acts as an open. Q-19. What term is used to describe the frequency at which the filter circuit changes from the point of rejecting the unwanted frequencies to the point of passing the desired frequencies?

A-19. Frequency cutoff (fco). Q-20. What type filter is used to allow a narrow band of frequencies to pass through a circuit and attenuate all other frequencies above or below the desired band?

A-20. Bandpass. Q-21. What type filter is used to block the passage of current for a narrow band of frequencies, while allowing current to flow at all frequencies above or below this band?

A-21. Band-reject.

VIDEO AND RF AMPLIFIERS

Q-1. What is the bandwidth of an amplifier? A-1. The difference between the upper and lower frequency limits of an amplifier. Q-2. What are the upper and lower frequency limits of an amplifier? A-2. The half-power points of a frequency-response curve. The upper and lower limits of the band f frequencies for which the amplifier is most effective. Q-3. What are the upper and lower frequency limits and the bandwidth for the amplifiers that have frequency-response curves as shown in figure 2-3? A-3. (A) f2 = 80 kHz, f1 = 30 kHz, BW = 50 kHz (B) f2 = 4 kHz, f1 = 2 kHz, BW = 2 kHz Q-4. What are the factors that limit the frequency response of a transistor amplifier? A-4. The capacitance and inductance of the circuit and the interelectrode capacitance of the transistor. Q-5. What type of feedback is usually caused by interelectrode capacitance?

A-5. Negative (degenerative) feedback. Q-6. What happens to capacitive reactance as frequency increases?

A-6. It decreases. Q-7. What happens to inductive reactance as frequency increases?

A-7. It increases. Q-8. What is the major factor that limits the high-frequency response of an amplifier circuits?

A-8. The capacitance of the circuit. Q-9. What components can be used to increase the high-frequency response of an amplifier?

A-9. Peaking coils. Q-10. What determines whether these components are considered series or shunt?

A-10. The relationship of the components to the output-signal path. Q-11. What is the arrangement of both series and shunt components called?

A-11. Combination peaking. Q-12. What component in an amplifier circuit tends to limit the low-frequency response of the amplifier?

A-12. The coupling capacitor (C3).

Q-13. What is the purpose of L3?

A-13. A shunt peaking coil for Q2.

Q-14. What is the purpose of C1?

A-14. A decoupling capacitor for the effects of R2.

Q-15. What is the purpose of R4?

A-15. A part of the low-frequency compensation network for Q1.

Q-16. What is the purpose of L2?

A-16. A series peaking coil for Q1.

Q-17. What is the purpose of R5?

A-17. A swamping resistor for L2. Q-18. What component(s) is/are used for high-frequency compensation for Q1?

A-18. L1, L2, and R5. Q-19. What component(s) is/are used for low-frequency compensation for Q2?

A-19. R9 and C5. Q-20. If the input-signal-developing impedance of an amplifier is increased, what is the effect on the gain?

A-20. The gain increases. Q-21. If the output impedance of an amplifier circuit is decreased, what is the effect on the gain?

A-21. The gain decreases. Q-22. What is the purpose of a frequency-determining network in an rf amplifier?

A-22. To provide maximum impedance at the desired frequency. Q-23. Can a parallel LC circuit be used as the frequency-determining network for an rf amplifier?

A-23. Yes. Q-24. How can the frequency be changed in the frequency-determining network?

A-24. By changing the value. Q-25. What is the most common form of coupling for an rf amplifier?

A-25. Transformer coupling.

Q-26. What are two advantages of this type of coupling? A-26. It uses fewer components than capacitive coupling and can provide an increase in gain.

NEETS Q&A

Q-27. If current gain is required from an rf amplifier, what type of component should be used as an output coupling element?

A-27. A step-down transformer. Q-28. What problem is caused in an rf amplifier by a loosely coupled transformer?

A-28. A too-narrow bandpass.

Q-29. How is this problem corrected?

A-29. By using an optimumly-coupled transformer.

Q-30. What problem is caused by overcoupling in a transformer?

A-30. Low gain at the center frequency.

Q-31. What method provides the widest bandpass?

A-31. A swamping resistor in parallel with the tuned circuit. Q-32. What two methods are used to compensate for the problems that cause low gain in an rf amplifier?

A-32. RF transformers are used and the transistor is neutralized. Q-33. What type of feedback is usually caused by the base-to-collector interelectrode capacitance?

A-33. Degenerative or negative.

Q-34. How is this compensated for? A-34. By neutralization such as the use of a capacitor to provide regenerative (positive) feedback. Q-35. What components form the input-signal-developing impedance for the amplifier?

A-35. C2 and the secondary of T1.

Q-36. What is the purpose of R1?

A-36. R1 provides the proper bias to the base of Q1 from VBB .

Q-37. What is the purpose of R2?

A-37. R2 provides the proper bias to the emitter of Q1. Q-38. If C4 were removed from the circuit, what would happen to the output of the amplifier? A-38. The output would decrease. (C4 decouples R2 preventing degenerative feedback from R2.)

Q-39. What components form the load for Q1?

A-39. C5 and the primary of T2. Q-40. How many tuned parallel LC circuits are shown in this schematic?

A-40. Four. Q-41. What do the dotted lines connecting C1, C2, C5, and C6 indicate? A-41. The dotted lines indicate that these capacitors are "ganged" and are tuned together with a single control.

Q-42. What is the purpose of C3?

A-42. C3 provides neutralization for Q1.

WAVE PROPAGATION

Q1. What is propagation?

A1. Propagation means spreading out.

Q2. How is a wave defined as it applies to wave propagation?

A2. A wave is a disturbance which moves through a medium.

Q3. What is wave motion?

A3. A means of transferring energy from one place to another.

Q4. What are some examples of wave motion? A4. Sound waves, light waves, radio waves, heat waves, water waves. Q5. What type of wave motion is represented by the motion of water?

A5. Transverse waves.

Q6. What are some examples of transverse waves?

A6. Radio waves, light waves, and heat waves.

Q7. What example of a longitudinal wave was given in the text?

A7. A sound wave. Q8. What are the three requirements for a wave to be propagated?

A8. A source, medium, and detector (receiver).

Q9. What is a cycle? A9. A sequence of events, such as the positive and negative alternation of electrical current.

Q10. What is wavelength (λ)? A10. The space occupied by one cycle of a radio wave at any given instant.

Q11. What is the law of reflection? A11. The law of reflection states: The angle of incidence is equal to the angle of reflection.

Q12. When a wave is reflected from a surface, energy is transferred. When is the transfer of energy greatest?

A12. When the incident wave is nearly parallel with the surface.

Q13. When is the transfer of energy minimum? A13. When the incident wave is perpendicular to the surface. Also a dull (or black) surface reflects very little regardless of the angle. Q14. A refracted wave occurs when a wave passes from one medium into another medium. What determines the angle of refraction?

A14. The density of the two mediums, and the velocity of the waves. Q15. The apparent change in frequency or pitch because of motion is explained by what effect?

A15. The Doppler effect. Q16. What term describes sounds capable of being heard by the human ear?

A16. Sonics.

Q17. Are all sounds audible to the human ear? Why? A17. No. The average human ear cannot hear all sounds in the infrasonic and ultrasonic regions. Q18. Sound waves transmitted from a source are sometimes weak when they reach the detector. What instrument is needed to boost the weak signal?

A18. An amplifier.

Q19. What are the three basic requirements for sound?

A19. A source, medium, and detector (receiver).

Q20. What are the two general groups of sound?

A20. Noise and tones.

Q21. What are the three basic characteristics of sound?

A21. Pitch, intensity, and quality.

Q22. What is the normal audible range of the human ear?

A22. 20 Hz to 20 kHz.

Q23. What is intensity as it pertains to sound?

A23. The amount of energy transmitted from a source. Q24. What characteristic of sound enables a person to distinguish one musical instrument from another, if they are all playing the same note?

A24. Quality. Q25. How does density and temperature affect the velocity of sound? A25. Velocity increases as density decreases and temperature increases.

Q26. What term is used in describing the science of sound?

A26. Acoustics. Q27. A sound wave that is reflected back toward the source is known as what type of sound?

A27. Echo.

Q28. What is the term for multiple reflections of sound waves?

A28. Reverberation. Q29. A cavity that vibrates at its natural frequency produces a louder sound than at other frequencies. What term is used to describe this phenomenon?

A29. Resonance. Q30. What do we call a disturbance that distracts or distorts the quality of sound?

A30. Noise.

Q31. What are three means of producing light?

A31. Mechanical, electrical, and chemical.

Q32. What is the smallest unit of radiant energy?

A32. A photon. Q33. What unit is used to measure the different wavelengths of light?

A33. Angstrom unit.

Q34. What are the three primary colors of light?

A34. Red, green and blue.

Q35. What are the three secondary colors of light?

magenta, yellow, and cyan Q36. White light falls upon a dull, rough, dark-brown object. Will the light primarily be reflected, diffused, or absorbed by the object?

Q37. What color will be emitted by a dull, rough, black object when white light falls upon it?

Q38. A substance that transmits light but through which an object cannot be seen clearly is known as what kind of

NEETS Q&A

substance?

Q39. At what speed does light travel?

186,000 (1.86 x 10^5) miles per second. Q40. A light wave enters a sheet of glass at a perfect right angle to the surface. Is the majority of the wave reflected, refracted, transmitted, or absorbed?

Q41. When light strikes a piece of white paper, the light is reflected in all directions. What do we call this scattering of light?

Q42. What three examples of electromagnetic energy are mentioned in the text?

Q43. What is the main difference between the bulk of the electromagnetic spectrum and the visual spectrum?

Q44. What are the two components (fields) that make up the electromagnetic wave?

Q45. What do we call a conductor (or set of conductors) that radiates electromagnetic energy into space?

Q46. What do we call the field that is created between two rods when a voltage is applied to them?

Q47. When current flows through a conductor, a field is created around the conductor. What do we call this field?

Q48. An induction field is created around a conductor when current flows through it. What do we call the field that detaches itself from the conductor and travels through space?

WAVE SHAPING

Q1. Which portion of a sine-wave input is retained in the output of a series-positive limiter?

A1. Negative. Q2. Which portion of a sine-wave input is retained in the output of a series-negative limiter?

A2. Positive. Q3. How can a series-positive limiter be modified to limit unwanted negative portions of the input signal?

A3. Biasing. Q4. What component is in parallel with the output in a parallel limiter?

A4. The diode. Q5. What is the condition of the diode in a series limiter when an output is developed? In a parallel limiter?

A5. Conducting, cutoff. Q6. What is the relative length of the time constant for the diode-capacitor combination in a damper (long or short)?

A6. Short time constant. Q7. What is the relative length of the discharge time constant with respect to the charge time constant of a damper (long or short)?

A7. Long time constant. Q8. A positive damper clamps which extremity of the output signal to 0 volts?

A8. Most negative. Q9. To which polarity does a positive damper with positive bins clamp the most negative extremity of the output waveform (positive or negative)?

A9. Positive potential. Q10. What type damper (with bias) clamps the most negative extremity of the output waveform to a negative potential?

A10. Positive clamper with negative bias. Q11. A negative damper damps which extremity of the output waveshape to 0 volts?

A11. Most positive. Q12. A negative damper with negative bias clamps the most positive extremity of the output wave shape to what polarity (positive or negative)?

A12. Negative potential. Q13. What type of bias (positive or negative) is added to a negative damper for the most positive extremity of the wave shape to be clamped above 0 volts?

A13. Positive bias.

Q14. What would be the output of a negative clamper with a bias potential of −5 volts and an input voltage swing from +50 to −50 volts?

A14. -5 volts.

Q15. What is the harmonic composition of a square wave? A15. It is composed of an infinite number of odd harmonics in phase with the fundamental.

Q16. What is the peaked wave composed of? A16. It is composed of odd harmonics some of which are out phase with the fundamental. Q17. What is the fundamental difference between the phase relationship of the harmonics of the square wave as compared to the harmonics of a peaked wave? A17. All the odd harmonics are in phase with the fundamental in the square wave. This is not true of the odd harmonics in the peaked wave.

Q18. What are the requirements for an integration circuit? A18. The time constant is long and the output is taken across the capacitor in an RC circuit.

Q19. Can a pure sine wave be integrated? Why? A19. A pure sine wave cannot be integrated; it contains no harmonics. Q20. What characteristic of an RL circuit allows it to act as an integrator?

A20. The ability of the inductor to oppose a change in current. Q21. What is the numerical difference (in terms of the time constant) between a long and a short time constant circuit? A21. The time-constant value of a long time constant-circuit is 10 times the value of the input pulse duration. The short time-constant circuit has a time constant of 1/10 of the pulse duration. Q22. What would happen to the integrator output if the capacitor were made extremely large (all other factors remaining the same)? A22. A more complete integration of the waveform would result from the long time constant. Q23. What is the difference between an RC and an RL differentiator in terms of where the output is developed? A23. In an RC circuit the output is taken across the resistor. In the RL circuit the output is taken across the inductor.

Q24. Name a common application of counting circuits.

A24. Frequency counters or frequency dividers. Q25. What establishes the value of the current that flows in the output of figure 4-43?

A25. The frequency of the voltage input.

Q26. What is the purpose of D1 in figure 4-43?

A26. To provide a quick discharge path for C1. Q27. What is the difference between a positive counter and a step counter? A27. The load resistor in a positive counter is replaced by a capacitor in a step counter.

WAVEFORMS AND WAVE GENERATORS

Q1. What type circuit is used to produce square or rectangular waves?

A1. Multivibrator.

Q2. What type of multivibrator does not have a stable state?

A2. Astable.

Q3. What type of multvibrator has one stable state?

A3. Monostable.

Q4. What type of multivibrator has two stable states?

A4. Bistable. Q5. In an astable multivibrator, which components determine the pulse repetition frequency?

A5. RC coupling networks.

Q6. What is another name for the monostable multivibrator?

A6. One-shot. Q7. In a bistable multivibrator, how many trigger pulses are needed to produce one complete cycle in the output?

A7. Two.

Q8. How many stable states are there for a flip-flop?

A8. Two. Q9. If a voltage (positive or negative) is measured on the "1" output of a flip-flop, what state is it in?

A9. SET state. Q10. What component in a blocking oscillator controls pulse width?

A10. Transformer.

NEETS Q&A

Q11. For an RC circuit to produce a linear output across the capacitor, the voltage across the capacitor may not exceed what percent of the applied voltage?

A11. Ten percent. Q12. Increasing gate length in a sawtooth generator does what to linearity?

A12. Decreases linearity. Q13. In a sawtooth generator, why is the transistor turned on for a longer time than the discharge time of the RC network?

A13. To allow the capacitor time to discharge. Q14. What is added to a sawtooth generator to produce a trapezoidal wave?

A14. A resistor.

WAVEGUIDE THEORY AND APPLICATION

Q-1. What is the region of the frequency spectrum from 1000 MHz to 100,000 MHz called?

A-1. Microwave region.

Q-2. Microwave theory is based upon what concept

A-2. Electromagnetic field theory. Q-3. Why are coaxial lines more efficient at microwave frequencies than two-wire transmission lines?

A-3. The electromagnetic fields are completely confined. Q-4. What kind of material must be used in the construction of waveguides?

A-4. Conductive material. Q-5. The large surface area of a waveguide greatly reduces what type of loss that is common in two-wire and coaxial lines?

A-5. Copper loss. Q-6. What causes the current-carrying area at the center conductor of a coaxial line to be restricted to a small layer at the surface?

A-6. Skin effect.

Q-7. What is used as a dielectric in waveguides?

A-7. Air. Q-8. What is the primary lower-frequency limitation of waveguides?

A-8. Physical size. Q-9. At very high frequencies, what characteristics are displayed by ordinary insulators?

A-9. The characteristics of the dielectric of a capacitor. Q-10. What type of insulator works well at very high frequencies?

A-10. A shorted quarter-wave section called a metallic insulator. Q-11. The frequency range of a waveguide is determined by what dimensions?

A-11. The "a" dimension. Q-12. What happens to the bus bar dimensions of the waveguide when the frequency is increased?

A-12. The bus bar becomes wider. Q-13. When the frequency is decreased so that two quarter-wavelengths are longer than the "a" (wide) dimension of the waveguide, what will happen?

A-13. Energy will no longer pass through the waveguide. Q-14. What interaction causes energy to travel down a waveguide?

A-14. The interaction of the electric and magnetic fields. Q-15. What is indicated by the number of arrows (closeness of spacing) used to represent an electric field?

A-15. The relative strength of the field. Q-16. What primary condition must magnetic lines of force meet in order to exist?

A-16. Magnetic lines of force must form a continuous closed loop. Q-17. What happens to the H lines between the conductors of a coil when the conductors are close together?

A-17. The H lines cancel. Q-18. For an electric field to exist at the surface of a conductor, the field must have what angular relationship to the conductor?

A-18. The field must be perpendicular to the conductors. Q-19. When a wavefront is radiated into a waveguide, what happens to the portions of the wavefront that do not satisfy the boundary conditions?

A-19. Decrease to zero. Q-20. Assuming the wall of a waveguide is perfectly flat, what is the angular relationship between the angle of incidence and the angle of reflection?

A-20. The angles are equal.

Q-21. What is the frequency called that produces angles of incidence and reflection that are perpendicular to the waveguide walls?

A-21. Cutoff frequency. Q-22. Compared to the velocity of propagation of waves in air, what is the velocity of propagation of waves in waveguides?

A-22. Slower. Q-23. What term is used to identify the forward progress velocity of wavefronts in a waveguide?

A-23. Group velocity. Q-24. What term is used to identify each of the many field configurations that can exist in waveguides?

A-24. Mode of operation. Q-25. What field configuration is easiest to produce in a given waveguide?

A-25. Dominant mode. Q-26. How is the cutoff wavelength of a circular waveguide figured?

A-26. 1.71 times the diameter. Q-27. The field arrangements in waveguides are divided into what two categories to describe the various modes of operation?

A-27. Transverse electric (TE) and transverse magnetic (TM). Q-28. The electric field is perpendicular to the "a" dimension of a waveguide in what mode?

A-28. TE. Q-29. The number of half-wave patterns in the "b" dimension of rectangular waveguides is indicated by which of the two descriptive subscripts?

A-29. Second. Q-30. Which subscript, in circular waveguide classification, indicates the number of full-wave patterns around the circumference?

A-30. First. Q-31. What determines the frequency, bandwidth, and power-handling capability of a waveguide probe?

A-31. Size and shape.

Q-32. Loose or inefficient coupling of energy into or out of a waveguide can be accomplished by the use of what method?

A-32. Slots and apertures. Q-33. What is the result of an impedance mismatch in a waveguide? A-33. Standing waves that cause power losses, a reduction in power-handling capability, and an increase in frequency and sensitivity.

Q-34. What is used to construct irises?

A-34. Metal plates. Q-35. An iris placed along the "b" dimension wall produces what kind of reactance?

A-35. Inductive. Q-36. How will an iris that has portions along both the "a" and "b" dimension walls act at the resonant frequency?

A-36. As a shunt resistance. Q-37. What device is used to produce a gradual change in impedance at the end of a waveguide?

A-37. Horn. Q-38. When a waveguide is terminated in a resistive load, the load must be matched to what property of the waveguide?

A-38. Characteristic impedance.

Q-39. What is the primary purpose of a dummy load?

A-39. Absorb all energy without producing standing waves. Q-40. The energy dissipated by a resistive load is most often in what form?

A-40. Heat. Q-41. What is the result of an abrupt change in the size, shape, or dielectric of a waveguide?

A-41. Reflections.

Q-42. A waveguide bend must have what minimum radius?

A-42. Greater than 2 wavelengths.

Q-43. What is the most common type of waveguide joint?

A-43. Choke joint. Q-44. What is the most likely cause of losses in waveguide systems?

A-44. Improperly connected joints or damaged inner surface.

Q-45. What is the primary purpose of a directional coupler?

A-45. Sampling energy within a waveguide. Q-46. How far apart are the two holes in a simple directional coupler?

A-46. 1/4 wavelength.

NEETS Q&A

Q-47. What is the purpose of the absorbent material in a directional coupler? A-47. Absorb the energy not directed at the pick-up probe and a portion of the overall energy. Q-48. In a directional coupler that is designed to sample the incident energy, what happens to the two portions of the wavefront when they arrive at the pickup probe?

A-48. The wavefront portions add. Q-49. What happens to reflected energy that enters a directional coupler that is designed to sample incident energy? A-49. The reflected energy adds at the absorbent material and is absorbed. Q-50. What two variables determine the primary frequency of a resonant cavity?

A-50. Size and shape of the cavity. Q-51. Energy can be inserted or removed from a cavity by what three methods?

A-51. Probes, loops, and slots. Q-52. Inductive tuning of a resonant cavity is accomplished by placing a nonmagnetic slug in what area?

A-52. The area of maximum H lines.

Q-53. What are the two basic types of T junctions?

A-53. E-type and H-type.

Q-54. Why is the H-type T junction so named? A-54. The junction arm extends in a direction parallel to the H lines in the main waveguide. Q-55. The magic-T is composed of what two basic types of T junctions?

A-55. E-type and H-type.

Q-56. What are the primary disadvantages of the magic-T?

A-56. Low power-handling capability and power losses. Q-57. What type of junctions are formed where the arms of a hybrid ring meet the main ring?

A-57. Basic E-type junctions.

Q-58. Hybrid rings are used primarily for what purpose?

A-58. High-power duplexes. Q-59. Ferrite devices are useful in microwave applications because they possess what properties?

A-59. Magnetic properties and high resistance. Q-60. Which of the two types of electron motion (orbital movement and electron spin) is more important in the explanation of magnetism?

A-60. Electron spin. Q-61. The interaction between an external field and the binding force of an atom causes electrons to do what?

A-61. Wobble at a natural resonant frequency. Q-62. The resonant frequency of electron wobble can be changed by variation of what force?

A-62. The applied magnetic field. Q-63. Rotating the plane of polarization of a wavefront by passing it through a ferrite device is called what?

A-63. Faraday rotation.

WIRING TECHNIQUES Q1. What are the basic requirements for any splice or terminal connection? A1. The connection must be both mechanically and electrically as strong as the conductor or device with which it is used

Q2. What is the preferred method for stripping wire?

A2. By use of a wire-stripping tool Q3. What stripping tool would NOT be used to strip glass braid insulation?

A3. Hot-blade stripper.

Q4. What tool should be used to strip aluminum wire?

A4. Knife. Q5. Why are the ends of the wire clamped down after a Western Union splice is made?

A5. To prevent damage to the tape insulation.

Q6. Why are splices staggered on multiconductor cables?

A6. To prevent the joint from being bulky.

Q7. Where is the rattail joint normally used?

A7. When wires are in conduit and a junction box is used. Q8. Which type of splice is used to splice a lighting fixture to a branch circuit?

A8. Fixture joint.

Q9. Which of the splices discussed is NOT a butted splice?

A9. Knotted tap joint.

Q10. Why is friction tape used in splicing?

A10. As a protective covering over the rubber tape. Q11. What is a major advantage of the crimped terminal over the soldered terminal?

A11. Requires relatively little operator skill to install. Q12. What are the two types of insulation most commonly used for noninsulated splices and terminal lugs?

A12. Spaghetti or heat-shrinkable tubing. Q13. What is the maximum allowable temperature that should be used on heat-shrinkable tubing?

A13. 300º F Q14. What is the maximum allowable source pressure that can be used with the compressor air/nitrogen heating tool?

A14. 200 psig. Q15. Should aluminum wire be cleaned prior to installing an aluminum terminal lug or splice? A15. No, it is done automatically by the petroleum abrasive compound that comes in the terminal or splices. Q16. What tools should be used to install large aluminum terminal lugs and splices?

A16. Power-operated crimping tools. Q17. Why should a lockwasher never be used with an aluminum terminal?

A17. It gouges the terminal lug and causes deterioration. Q18. What is the most common method of terminating and splicing wires?

A18. The use of preinsulated splices and terminal lugs. Q19. Besides not having to insulate a noninsulated terminal, what other advantage is gained by using a preinsulated terminal lug? A19. It has insulation support for extra supporting strength of the wire insulation.

Q20. Why are preinsulated terminal lugs and splices color coded?

A20. To identify wire sizes they are to be used on. Q21. Why must items to be soldered be cleaned just prior to the soldering process?

A21. Solder will not adhere to dirty, greasy, or oxidized surfaces.

Q22. What does "tinning" mean in relationship to soldering? A22. The coating of the material to be soldered with a light coat of solder. Q23. Why should wire be stripped 1/32 inch longer than the depth of the solder barrel? A23. To prevent burning the insulation during the soldering process and to allow the wire to flex easier at a stress point. Q24. How much of the stripped length of a conductor should be tinned?

A24. One-half the stripped length.

Q25. What causes a "fractured solder" joint?

A25. Movement of the parts being soldered while the solder is cooling.

Q26. Define thermal inertia. A26. The capacity of the soldering iron to generate and maintain a satisfactory soldering temperature while giving up heat to the joint being soldered. Q27. Why are small-wattage soldering irons not used to solder large conductors? A27. Although its temperature is as high as the larger irons, it does not have thermal inertia.

Q28. State why a well-designed soldering iron is self-regulating. A28. The resistance of its heating element increases with rising temperature, thus limiting the current flow.

Q29. What should be done to a soldering iron tip that is pitted?

A29. File the tip until it is smooth and retin it. Q30. What happens if a soldering gun switch is pressed for periods longer than 30 seconds? A30. It will overheat and could burn the insulation of the wire being soldered. Q31. What causes the nuts or screws that hold the tips on soldering irons and guns to loosen?

A31. The heating and cooling cycles.

Q32. A soldering gun should NOT be used on what components? A32. Electronic components, such as resistors, capacitors, and transistors. Q33. What is an advantage of using a resistance soldering iron when soldering wire to a connector? A33. The soldering tips are hot only during the brief period of soldering the connection, thus minimizing the chance of burning the wire insulation or connector inserts. Q34. Why is steel wool NEVER used as an abrasive to clean soldering tools? A34. The strands can fall into electrical equipment being worked on and cause short circuits.

NEETS Q&A

Q35. Why should "antiseize" compound be used on the screw-in tips of the pencil iron? A35. It enables the tip to be removed easily when another is to be inserted. Q36. If no suitable tip is available for a particular job, how may one be improvised? A36. Wrap a length of copper wire around one of the regular tips and bend to the proper shape for the purpose.

Q37. What two metals are used to from soft solder?

A37. Tin and lead. Q38. Define the metal solvent action that takes place when copper conductors are soldered together. A38. The solder dissolves a small amount of the copper, which combines with the solder forming a new alloy; therefore, the joint is one common metal. Q39. What is the tin-lead alloy percentage of solder used for electrical connectors, splices, and terminal lugs?

A39. 60-percent tin and 40-percent lead (60/40 solder).

Q40. What purpose does flux serve in the soldering process? A40. It cleans the metal by removing the oxide layer and prevents further oxidation during the soldering. Q41. What type of flux must be used in all electrical and electronic soldering?

A41. Noncorrosive, nonconductive rosin fluxes.

Q42. Why are solvents used in the soldering process?

A42. To remove contaminants from soldered connections.

Q43. What is the purpose of a heat shunt?

A43. To prevent damage to heat-sensitive components. Q44. Besides presenting a neat appearance and supporting each other, what is the other purpose for lacing conductors? A44. To aid in tracing the conductors when alterations or repairs are required. Q45. Why is flat tape preferred instead of round cord when wire bundles are laced?

A45. Round cord has a tendency to cut into the wire insulation. Q46. What amount of flat tape or round cord is required to single lace a group of conductors? A46. Two and one-half times the length of the longest conductor in the group.

Q47. What is the purpose of a lacing shuttle?

A47. To keep the tape or cord from fouling during the lacing operation.

Q48. When should wires be twisted prior to lacing? A48. When required, such as for the filament leads in electron tube amplifiers. Q49. What precautions should you take when tying bundles containing coaxial cables?

A49. Do not tie too tightly and use the proper type of tape.

Q50. How is the single lace started?

A50. With a square knot and at least two marling hitches drawn tightly.

Q51. What size wire bundles require double lace?

A51. Bundles that are 1 inch or larger in diameter

Q52. How is the double lace started?

A52. With a telephone hitch.

Q53. How are laced cable groups bound together?

A53. They are bound together at intervals with telephone hitches.

Q54. When are spot ties used? A54. When wire bundles are supported by cable supports that are more than 12 inches apart.

Q55. What is used to install self-clinching cable straps?

A55. Military Standard hand tool.

Q56. What is used to tie wire bundles in high-temperature areas?

A56. High-temperature, pressure-sensitive tape.