technician license class gordon west technician class manual pages 132-141 bandwidth &...

Technician Technician License ClassLicense Class

Gordon West Gordon West Technician Class ManualTechnician Class ManualPages 132-141Pages 132-141

Bandwidth & Bandwidth & InterferenceInterference

Presented byPresented by

Heart Of Texas Heart Of Texas Amateur Radio ClubAmateur Radio Club

(HOTARC)(HOTARC)

Bandwidth & InterferenceBandwidth & Interference 22

Bandwidth and Types of ModulationBandwidth and Types of Modulation

See pages 132 – 135…See pages 132 – 135…

Key words:Key words:

– CW, phone, FM, fast-scan TVCW, phone, FM, fast-scan TV

– Single sidebandSingle sideband

First, let’s look at the big picture…First, let’s look at the big picture…


Common Signal BandwidthsCommon Signal Bandwidths

CW: 5-10 HzCW: 5-10 Hz

DigitalDigital– PSK31: 31 HzPSK31: 31 Hz– RTTY: 250 HzRTTY: 250 Hz

Phone (Voice)Phone (Voice)– SSB: 2-3 kHzSSB: 2-3 kHz– AM: 4-6 kHzAM: 4-6 kHz– FM: 5-15 kHzFM: 5-15 kHz

Slow Scan TV:Slow Scan TV: 3 kHz3 kHz

Fast Scan TV:Fast Scan TV: 6 MHz !!6 MHz !!

FM: Over twice SSB


T6 A06 T6 A06 (pg 132)(pg 132)

Which emission type has the narrowest Which emission type has the narrowest bandwidth?bandwidth?

A.A. FM voiceFM voice

B.B. SSB voiceSSB voice

C.C. CWCWD.D. Slow-scan TVSlow-scan TV


T6A01 T6A01 (pg 132)(pg 132)

What are phone transmissions?What are phone transmissions?A.A. The use of telephones to set up an amateur The use of telephones to set up an amateur

radio contactradio contactB.B. A phone patch between amateur radio and A phone patch between amateur radio and

the telephone systemthe telephone system

C.C. Voice transmissions by radioVoice transmissions by radioD.D. Placing the telephone handset near a radio Placing the telephone handset near a radio

transceiver's microphone and speaker to transceiver's microphone and speaker to relay a telephone callrelay a telephone call


T6 A05 T6 A05 (pg 132)(pg 132)

Which type of modulation is most commonly Which type of modulation is most commonly used for VHF and UHF voice repeaters?used for VHF and UHF voice repeaters?A.A. AMAMB.B. SSBSSBC.C. PSKPSK

D.D. FMFM

Think of the quiet quality of “FM broadcast radio.” Think of the quiet quality of “FM broadcast radio.” We mainly use SSB (narrower) on the HF bands, We mainly use SSB (narrower) on the HF bands, where the spectrum is so “precious.”where the spectrum is so “precious.”


T6 A10 T6 A10 (pg 132)(pg 132)

What is the approximate bandwidth of a What is the approximate bandwidth of a frequency-modulated voice signal?frequency-modulated voice signal?A.A. Less than 500 HzLess than 500 HzB.B. About 150 kHzAbout 150 kHz

C.C. Between 5 and 15 kHzBetween 5 and 15 kHzD.D. More than 30 kHzMore than 30 kHz

Again, think of FM signals as over twice the Again, think of FM signals as over twice the width of SSB (which is 2-3 kHz).width of SSB (which is 2-3 kHz).

2 2 × 2.5 kHz = 5 kHz× 2.5 kHz = 5 kHz


T6 A11 T6 A11 (pg 133)(pg 133)

What is the normal bandwidth required for a What is the normal bandwidth required for a conventional conventional fast-scan TVfast-scan TV transmission using transmission using combined video and audio on the 70-centimeter combined video and audio on the 70-centimeter band? band?

A.A. More than 10 MHzMore than 10 MHz

B.B. About 6 MHzAbout 6 MHzC.C. About 3 MHzAbout 3 MHz

D.D. About 1 MHzAbout 1 MHz

Not just 6 kHz, butNot just 6 kHz, but 6000 kHz!!6000 kHz!!


T6 C04 T6 C04 (pg 133)(pg 133)

What type of transmission is indicated by What type of transmission is indicated by the term the term NTSCNTSC? ? A.A. A Normal Transmission mode in Static CircuitA Normal Transmission mode in Static CircuitB.B. A special mode for earth satellite uplinkA special mode for earth satellite uplink

C.C. A standard A standard fast scanfast scan color color television signaltelevision signal

D.D. A frame compression scheme for TV signalA frame compression scheme for TV signal

Just remember that Just remember that NTSCNTSC is what we all grew up is what we all grew up watching! Today’s kids will only know digital TV!watching! Today’s kids will only know digital TV!


T6 A02 T6 A02 (pg 134)(pg 134)

Which of the following is a form of Which of the following is a form of amplitude modulationamplitude modulation? ? A.A. Frequency modulationFrequency modulationB.B. Phase modulationPhase modulation

C.C.Single sidebandSingle sidebandD.D. Phase shift keyingPhase shift keying

Remember that SSB is Remember that SSB is just half of an AM signal just half of an AM signal (amplitude modulation).(amplitude modulation).


T6 A09 T6 A09 (pg 135)(pg 135)

What is the approximate bandwidth of a What is the approximate bandwidth of a single-sideband voice signal? single-sideband voice signal?

A.A. 1 kHz1 kHz

B.B. 2 kHz2 kHz

C.C. Between 3 and 6 kHzBetween 3 and 6 kHz

D.D. Between 2 and 3 kHzBetween 2 and 3 kHz

Have you got it yet? Have you got it yet? A SSB signal is about 3 kHz wide.A SSB signal is about 3 kHz wide.


T6 A08 T6 A08 (pg 135)(pg 135)

What is the primary advantage of single What is the primary advantage of single sideband over FM for voice transmissions? sideband over FM for voice transmissions?

A.A. SSB signals are easier to tune in SSB signals are easier to tune in than FM signalsthan FM signals

B.B. SSB signals are less likely to be bothered by SSB signals are less likely to be bothered by noise interference than FM signals.noise interference than FM signals.

C.C. SSB signals use much less bandwidth SSB signals use much less bandwidth than FM signalsthan FM signals

D.D. SSB signals have no advantages at all in SSB signals have no advantages at all in comparison to other modes.comparison to other modes.


Interference: A Very Dirty Word!Interference: A Very Dirty Word!

See pages 135 – 141…See pages 135 – 141…

Key words:Key words:

– Interference!Interference!

– Your stationYour station

– Your neighborsYour neighbors

– Telephones are often poorly designedTelephones are often poorly designed

– Strong signalsStrong signals


T3 D07 T3 D07 (pg 135)(pg 135)

What effect might a break in a cable television What effect might a break in a cable television transmission line have on amateur communications? transmission line have on amateur communications? A.A. A break cannot affect amateur communicationsA break cannot affect amateur communicationsB.B. Harmonic radiation from the TV may cause the Harmonic radiation from the TV may cause the

amateur transmitter to transmit off-frequencyamateur transmitter to transmit off-frequency

C.C. TV TV interferenceinterference may result when the may result when the amateur station is transmitting, or amateur station is transmitting, or interference may occur to the amateur interference may occur to the amateur receiverreceiver

D.D. The broken cable may pick up very high voltages The broken cable may pick up very high voltages when the amateur station is transmittingwhen the amateur station is transmitting

Think of it as a “leak”—unwanted signals either leak out or leak in.


T5 D08 T5 D08 (pg 136)(pg 136)

What is the proper course of action to take when a What is the proper course of action to take when a neighbor reports that your radio signals are interfering neighbor reports that your radio signals are interfering with something in his home? with something in his home? A.A. You are not required to do anythingYou are not required to do anythingB.B. Contact the FCC to see if other interference reports Contact the FCC to see if other interference reports

have been filedhave been filed

C.C. Check your stationCheck your station and make sure it meets and make sure it meets the standards of good amateur practicethe standards of good amateur practice

D.D. Change your antenna polarization from vertical to Change your antenna polarization from vertical to horizontalhorizontal


T5 D05 T5 D05 (pg 136)(pg 136)

What should you do first if someone tells you that your What should you do first if someone tells you that your transmissions are interfering with their TV reception? transmissions are interfering with their TV reception?

A.A. Make sure that Make sure that your stationyour station is operating is operating properly and that it does not cause properly and that it does not cause interference to your own televisioninterference to your own television

B.B. Immediately turn off your transmitter and contact the Immediately turn off your transmitter and contact the nearest FCC office for assistancenearest FCC office for assistance

C.C. Tell them that your license gives you the right to trans-mit Tell them that your license gives you the right to trans-mit and nothing can be done to reduce the interferenceand nothing can be done to reduce the interference

D.D. Continue operating normally because your equipment Continue operating normally because your equipment cannot possibly cause any interferencecannot possibly cause any interference


T3 D02 T3 D02 (pg 137)(pg 137)Who is responsible for taking care of the interference if Who is responsible for taking care of the interference if signals from your transmitter are causing front end signals from your transmitter are causing front end overload in your neighbor's television receiver? overload in your neighbor's television receiver? A.A. You alone are responsible, since your transmitter is You alone are responsible, since your transmitter is

causing the problemcausing the problemB.B. Both you and the owner of the television receiver Both you and the owner of the television receiver

share the responsibilityshare the responsibilityC.C. The FCC must decide if you or the owner of the The FCC must decide if you or the owner of the

television receiver is responsibletelevision receiver is responsible

D.D. The owner of the television receiver is The owner of the television receiver is responsibleresponsible

Note Gordon’s comments on this question.Note Gordon’s comments on this question.


T5 D09 T5 D09 (pg 137)(pg 137)

What should you do if a "Part 15" device in your neighbor’s What should you do if a "Part 15" device in your neighbor’s home is causing harmful interference to your amateur home is causing harmful interference to your amateur station? station?

A.A. Work with your neighborWork with your neighbor to identify the offending to identify the offending devicedevice

B.B. Politely inform your neighborPolitely inform your neighbor about the rules that about the rules that require him to stop using the device if it causes require him to stop using the device if it causes interferenceinterference

C.C. Check your stationCheck your station and make sure it meets the and make sure it meets the standards of good amateur practicestandards of good amateur practice

D.D. All of these answers are correctAll of these answers are correct


Low Pass, High Pass FiltersLow Pass, High Pass FiltersLow Pass

Frequency

Stop Band

Pass Band

40 dB

0 dB

fc

-3 dB

High Pass

Frequency

Pass Band

Stop Band

0 dB

40 dB

-3 dB

fc


Band Pass FilterBand Pass Filter

Stop Band

High Frequency

Low Frequency

40 dB

0 dB

fcfc

-3 dB

Stop Band

Pass Band


Notch (Band Stop) FilterNotch (Band Stop) Filter

Stop Band

High Frequency

Low Frequency

40 dB

0 dB

fcfc

-3 dB

Pass Band

Pass Band

Repeaters use cavity notch filters that have very sharp skirts to keep the transmitter from interfering with the receiver, since they’re both active at the same time on very close frequencies.

Want to “stop” (be deaf to) nearby transmitter on this

frequency


T5 A07 T5 A07 (pg 137)(pg 137)

What type of filter should be connected to a TV What type of filter should be connected to a TV receiver as the first step in trying to prevent RF receiver as the first step in trying to prevent RF overload from a nearby 2-meter transmitter? overload from a nearby 2-meter transmitter? A.A. Low-pass filterLow-pass filterB.B. High-pass filterHigh-pass filterC.C. Band pass filterBand pass filter

D.D. Notch filterNotch filterJust like those notch filters used for repeaters, this sends the unwanted frequencies to ground.Note Gordon’s caution on pg 138.


T3 D03 T3 D03 (pg 138)(pg 138)

What is the major cause of telephone interference? What is the major cause of telephone interference?

A.A. The telephone wiring is inadequateThe telephone wiring is inadequate

B.B. Tropospheric ducting at UHF frequenciesTropospheric ducting at UHF frequencies

C.C. The telephone was not equipped with The telephone was not equipped with adequate adequate interferenceinterference protection when protection when manufactured.manufactured.

D.D. Improper location of the telephone in the homeImproper location of the telephone in the home

Poorly designed?


T5 D03 T5 D03 (pg 138)(pg 138)

What is the most likely cause of telephone What is the most likely cause of telephone interference from a nearby transmitter? interference from a nearby transmitter?

A.A. Harmonics from the transmitterHarmonics from the transmitter

B.B. The transmitter's signals are causing The transmitter's signals are causing the telephone to act like a radio the telephone to act like a radio receiverreceiver

C.C. Poor station groundingPoor station grounding

D.D. Improper transmitter adjustmentImproper transmitter adjustment

Poorly designed?


T5 D04 T5 D04 (pg 138)(pg 138)

What is a logical first step when attempting to What is a logical first step when attempting to cure a radio frequency interference problem in a cure a radio frequency interference problem in a nearby telephone?nearby telephone?

A.A. Install a low-pass filter at the transmitterInstall a low-pass filter at the transmitter

B.B. Install a high-pass filter at the transmitterInstall a high-pass filter at the transmitter

C.C. Install an RF filter at the telephoneInstall an RF filter at the telephoneD.D. Improve station groundingImprove station grounding

Poorly designed?


Telephone FilterTelephone Filter

These filters are only effective if the signal is coming through the phone line. If it is being picked up by the telephone’s circuitry directly, there is no filter that can remove it.


T5 D07 T5 D07 (pg139)(pg139)

Which of the following may be useful in Which of the following may be useful in correcting a radio frequency interference correcting a radio frequency interference problem? problem?

A.A. Snap-on ferrite chokesSnap-on ferrite chokes

B.B. Low-pass and high-pass filtersLow-pass and high-pass filters

C.C. Notch and band-pass filtersNotch and band-pass filters

D.D. All of these answers are correctAll of these answers are correct

The FCC likes filters, filters, filters!The FCC likes filters, filters, filters!


T5 D02 T5 D02 (pg 139)(pg 139)

Which of the following is Which of the following is NOTNOT a cause of radio a cause of radio frequency interference? frequency interference?

A.A. Fundamental overloadFundamental overload

B.B. Doppler shiftDoppler shiftC.C. Spurious emissionsSpurious emissions

D.D. HarmonicsHarmonics


T5 D10 T5 D10 (pg 139)(pg 139)

What could be happening if another operator tells you What could be happening if another operator tells you he is hearing a variable high-pitched whine on the he is hearing a variable high-pitched whine on the signals from your signals from your mobilemobile transmitter? transmitter? A.A. Your microphone is picking up noise from an open Your microphone is picking up noise from an open

windowwindowB.B. You have the volume on your receiver set too highYou have the volume on your receiver set too highC.C. You need to adjust your squelch controlYou need to adjust your squelch control

D.D. The power wiring for your radio is picking The power wiring for your radio is picking up noise from the up noise from the vehicle'svehicle's electrical electrical systemsystem


T9 B03 T9 B03 (pg 140)(pg 140)

What is the most likely cause of sudden bursts of What is the most likely cause of sudden bursts of tones or fragments of different conversations that tones or fragments of different conversations that interfere with VHF or UHF signals? interfere with VHF or UHF signals?

A.A. The batteries in your transceiver are failingThe batteries in your transceiver are failing

B.B. Strong signalsStrong signals are overloading the are overloading the receiver and causing undesired signals receiver and causing undesired signals to be heardto be heard

C.C. The receiver is picking up low orbit satellitesThe receiver is picking up low orbit satellites

D.D. A nearby broadcast station is having transmitter A nearby broadcast station is having transmitter problemsproblems


T3 D11 T3 D11 (pg 140)(pg 140)

What is meant by receiver front-end overload? What is meant by receiver front-end overload?

A.A. Too much voltage from the power supplyToo much voltage from the power supply

B.B. Too much current from the power supplyToo much current from the power supply

C.C. Interference caused by Interference caused by strong signalsstrong signals from a nearby sourcefrom a nearby source

D.D. Interference caused by turning the volume up Interference caused by turning the volume up too hightoo high


T5 D01 T5 D01 (pg 140)(pg 140)

What is meant by fundamental overload in What is meant by fundamental overload in reference to a receiver? reference to a receiver?

A.A. Too much voltage from the power supplyToo much voltage from the power supply

B.B. Too much current from the power supplyToo much current from the power supply

C.C. Interference caused by very Interference caused by very strong strong signalssignals from a nearby source from a nearby source

D.D. Interference caused by turning the volume up Interference caused by turning the volume up too hightoo high


T3 D01 T3 D01 (pg 140)(pg 140)

What should you do if you receive a report that What should you do if you receive a report that your transmissions are causing splatter or your transmissions are causing splatter or interference on interference on nearby frequenciesnearby frequencies? ?

A.A. Increase transmit powerIncrease transmit power

B.B. Change mode of transmissionChange mode of transmission

C.C. Report the interference to the equipment Report the interference to the equipment manufacturermanufacturer

D.D. Check transmitter for Check transmitter for off frequencyoff frequency operation or spurious emissionsoperation or spurious emissions


T5 A06 T5 A06 (pg 141)(pg 141)

Where must a filter be installed to reduce Where must a filter be installed to reduce spurious spurious emissionsemissions? ?

A.A. At the transmitterAt the transmitterB.B. At the receiverAt the receiver

C.C. At the station power supplyAt the station power supply

D.D. At the microphoneAt the microphone


T7 A05 T7 A05 (pg 141)(pg 141)

What is a method used to locate sources of What is a method used to locate sources of noise interference or jamming? noise interference or jamming?

A.A. EcholocationEcholocation

B.B. Doppler radarDoppler radar

C.C.Radio direction findingRadio direction findingD.D. Phase lockingPhase locking

Also known as “RDF.” We stage “fox hunts” to Also known as “RDF.” We stage “fox hunts” to practice this skill.practice this skill.

technician license class gordon west technician class manual pages 132-141 bandwidth &...

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