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ECE ELECTIVE III
BROADCAST ENGINEERING AND ACOUSTICS
Course Content Introduction to AM Broadcasting System and
Standards Introduction to FM Broadcasting System and
Standards Introduction to TV Broadcasting System and
Standards Introduction to Engineering Acoustics Room Acoustics Speaker Systems, Speaker Enclosures and
Microphones Crossover and Dividing Networks
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
ECE ELECTIVE III
BROADCAST ENGINEERING AND ACOUSTICS
Introduction to AM Broadcasting System
and Standards
BroadcastingBroadcasting is the distribution of
audio and/or video signals (programs) to a number of recipients ("listeners" or "viewers") that belong to a large group.
Broadcasting to a very narrow range of audience is called narrowcasting.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Broadcasting The term "broadcast" was coined by early
radio engineers from the midwestern United States. "Broadcasting", in farming, is one method of spreading seed using a wide toss of the hand, in a broad cast.
Television and radio programs are distributed through radio broadcasting or cable, often both simultaneously.
Broadcasting forms a very large segment of mass media.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Amplitude Modulation (AM)The process of varying the
amplitude of a high-frequency carrier wave in accordance with the amplitude of the modulating signal.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
EM Spectrum Properties
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
EM Spectrum Properties
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Uses of AM1. Broadcasting Long wave AM Radio 148.5 – 283.5 kHz
(LF) Medium wave AM Radio 530 kHz – 1710 kHz (MF) International Shortwave AM Radio 3 MHz – 30 MHz
(HF)
2. Citizen’s Band Radio (27 MHz)
3. Aircraft communications (108 – 136 MHz) 4. TV picture (using vestigial sideband)
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Limiting condition for AM:
The amplitude of the modulating signal must not exceed that of the carrier, else overmodulation (clipping) occurs.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
AM Broadcasting Standards (FCC) Frequency allocation: 535 to 1605 kHz (525 to
1705 kHz) divided into 106 (130) channels Channel spacing: 10 kHz (9 kHz) Permitted channel bandwidth: 30 kHz
(maximum modulating signal frequency: 15 kHz)*note: geographically co-located stations must be spaced at least 3 channels apart for sideband interference protection)
Carrier tolerance: ± 20 Hz Unmodulated carrier power: 100 W to 50 kW Type of emission: A3E (double sideband, full
carrier) Intermediate Frequency: 455 kHz
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
AM Broadcasting Standards (KBP) Frequency allocation: 526.5 to 1705 kHz
Start of carrier frequency: 531 kHz
Channel spacing: 9 kHz
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
AM Station PerformanceRequirements (FCC) Modulation percentage: 85% to 95% Audio frequency distortion
harmonics (AFDH): <5% rms amplitude up to 84% modulation
Audio frequency response: transmission characteristic must be flat from 100 Hz to 5 kHz (± 2 dB referred to 1 kHz)
Carrier stability: ± 20 Hz
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Service Areas in AMPrimary Area in which the ground wave field is measured at 1
mV/m, and is not subject to objectionable interference and fading
Secondary The area serviced by the sky wave, having a sky wave
field strength equal to or greater than 500 μV/m for 50% or more of the time. May be subject to fading but no objectionable co-channel interference
Intermittent The area receiving service from the ground wave but
beyond the primary service area and subject to objectionable interference and fading
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Times of Day in AM BroadcastingDaytime From local sunrise to local sunset 6 AM to 6 PM (2200 UTC to 1000 UTC)
Nighttime Between local sunset to local sunrise 6 PM to 6 AM (1000 UTC to 2200 UTC) Experimental period Midnight to local sunrise 12 MN to 6 AM (1600 UTC to 2200 UTC) Used for experimental purposes in testing and maintaining
apparatuses by the licensee, provided that no interference is caused to other stations maintaining a regular operating schedule within such a period
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
3 Important Requirements in Broadcasting1. Timing Programming schedule must be followed
(programs should start and end within the allotted time)
2. Fidelity Program material shall not have any reasonable
distortion3. Modulation depth The audio signal must modulate the transmitter
properly
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Power AllocationsAREA Maximum Permissible
Power
Metro Manila 50 kW
All other areas 10 kW
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
The transmitter of existing Metro Manila stations may be located outside of Metro Manila, provided that Metro Manila remains within the 80 dBu contour of the transmitter. The station shall not operate more than 5% and lower than 10% of its authorized operating power.
Classification of Powers1. Licensed power or authorized operating power That which is actually supplied or fed to the antenna by the
transmitter. Should have a tolerance of -5% or +10%
2. Maximum rated carrier power The maximum power that the transmitter is capable of
supplying to the antenna and still operate satisfactorily
3. Plate input power Product of the voltage and current at the output of the last
radio stage, measured without modulation 4. Antenna input power Product of the square of the antenna current and the
antenna resistance at the point where the current is measured.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Two methods of measuring antenna input power1. Direct method
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Where: Ia = antenna current w/ no modulationRa = impedance or resistance of the antenna where the current is measured2. Indirect method
• used to determine the output power of FM broadcast stations and TV aural transmitters
• used for AM broadcast stations in emergencies
Where:Vp = plate voltage of the final amplifierIp = plate current of the final amplifierF = power factor correction
AM Antennas and Site Considerations Standard AM broadcast stations use either a single
omnidirectional vertical antennas, or multi-element, phased vertical directional arrays
Generally, antennas are erected on flat lands, preferably those having good ground conductivities (e.g. marsh lands)
Earth mat – a network of buried wires directly under the antenna, extending outward from the base, buried about 6 to 12 inches (15 to 30 cm) below the ground
Counterpoise – a smaller version of the earth mat above ground
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Antenna Towers:Obstruction Painting and Lighting
Must be painted with equal-width stripes of aviation (emergency) orange and white, each stripe approximately one-seventh of the height of the tower, but not over 100 ft (30 m) in width on tall towers. The top and bottom stripes must be orange
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Antenna Towers:Obstruction Painting and Lighting
To mark the tower at night (sunset to sunrise), towers up to 150 ft (46 m) must have two (2) steady-burning 116-W or 125-W lamps in an aviation red light globe at the top of the tower (beacon)
For towers over 150 ft, the top beacon light consists of 620-W or 700-W PS-40 Flashing Code Beacon lamps with aviation red filters
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Antenna Towers:Obstruction Painting and Lighting
At half-, third-, quarter-, etc. tower height points (depending on the height of the tower), flashing 620-W to 700-W beacons are installed
Lights should be automatically controlled by a device sensitive to the night sky.
Lights should be inspected at least once a day, or by automatic indicators
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Broadcast Auxiliary ServicesA broadcast auxiliary service or BAS is any radio frequency system used by a radio station or TV station, which is not part of its direct broadcast to listeners or viewers. These are essentially internal-use backhaul channels not intended for actual reception by the public, but part of the airchain required to get those signals to such a transmitter.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
STUDIO-TO-TRANSMITTER LINK/REMOTE CONTROL SYTEM
The frequency band allocation for STUDIO-TO-TRANSMITTER LINK/REMOTE CONTROL SYTEM shall be: Band A 300-315 MHz Band B 734-752 MHz Band C 942-952 MHz The maximum power allowable for STL's
shall be 15 watts.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
REMOTE PICK-UP STATION
The frequency band allocation for REMOTE PICK-UP STATION shall be: Band A 315-325 MHz Band B 450-451 MHz Band C 455-456 MHz The maximum power allowable for
Remote Pick-up Stations shall be 35 watts.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
COMMUNICATIONS, COORDINATION AND CONTROL LINK
The frequency band allocation for COMMUNICATIONS, COORDINATION AND CONTROL LINK shall be: Band A 412 MHz (non-exclusive) Band B 25.67 - 26.1 MHz Band C 162.235 - 162.615 MHz
166.250 - 170.150 MHz Band D 432.5 - 433 MHz
437.5 - 438 MHz
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
COMMUNICATIONS, COORDINATION AND CONTROL LINK
The maximum power allowable for Communications, Coordination and Control Link shall be:
Band A - 100 watts (SBS)B - 160 watts (ERP)C - 160 watts (ERP)D - 200 watts (for repeater)
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
OPERATING REQUIREMENTS: Hours of Operation
Minimum Operating Schedule The licensee of each medium-frequency
broadcast station shall maintain a minimum operating schedule of two-thirds of the total hours that it is authorized to operate except that in emergencies when, due to causes beyond the control of the licensee, it becomes impossible to continue operating, the station may cease operations for a period not exceeding 10 days.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
OPERATING REQUIREMENTS: Hours of OperationMinimum Operating Schedule Broadcast(s) outside of the authorized regular
operating schedules (as before regular sign-on schedules and/or beyond the regular sign-off schedules) may be aired without prior authorization from the Authority provided the program falls under an emergency category or of very important relevance to the station's existence. The information shall be entered in the program and operating logs at the time the broadcast was aired.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
OPERATING REQUIREMENTS: Hours of Operation
Minimum Operating Schedule If a permanent discontinuance of
operations is being contemplated, then the licensee shall notify in writing the Authority or regional office where the station is located at least two (2) days before the actual discontinuance is effected.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Station identification Announcements A licensee of a medium-frequency
broadcast station shall make station identification announcements (call letters, frequency, and location) at the beginning and ending of each time of operation and during operation on the hour and either on the half hour or at the quarter hour preceding the next hour:
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Station identification Announcements Such identification announcement need not
be made on the half hour or quarter hour when, to make such announcement, would interrupt a single consecutive speech, play, religious service, symphony concert, or operatic production. In such cases, an identification announcement shall be made at the first interruption of the entertainment continuity and at the conclusion of. the program:
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Station identification Announcements Provided, that an announcement within five
minutes of either on the half hour or at the quarter hour preceding the next hour will satisfy the requirements of identification announcements. In the case of variety show programs, basketball game broadcasts, or similar programs of longer duration than 30 minutes, the identification announcement shall be made within 5 minutes of the times specified in the hours of operation.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Logs
Log A listing of the date and time of events,
programs, equipment parameters, tests, malfunctions, corrections, and other such information
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Types of Logs in Broadcast OperationsProgram Log Contains entries with regard to the nature of the program,
its name and title, start and end times, source, sponsors of announcements, duration of advertisements, etc.
Operating Log Contains the technical details of the transmitter during
operation, such as operating parameters (Vp, Ip, Ia, etc.), the time the transmitter is put on and off the air, the time antenna lights are turned on or off, etc.
Maintenance Log Contains the results of transmitter and other equipment
tests, repairs, calibration, checks, etc.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
AM STEREOPHONIC STANDARD The AM stereophonic standard is the C-
QUAM (Compatible Quadrature Amplitude Modulation) AM stereophonic system.
Stereophonic AM broadcasting involves the transmission of additional information with the monophonic signal on the AM carrier allowing the reception of the original monophonic signal and left and right stereophonic signals.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
AM STEREOPHONIC STANDARD The stereophonic audio information is composed
of two signals; left (L) and right (R). As in the present AM broadcast standards, the carrier is amplitude modulated by the sum (L+R) signal. The additional information in the form of the difference (L-R) signal is added to the carrier by quadrature phase modulation. A separate pilot signal is added to the difference signal to indicate the presence of a stereophonic broadcast.
C-QUAM is a registered trademark of Motorola Inc.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
PUBLIC INFORMATION FILEPublic Information File shall contain the following: A copy of the station license. Documents as to mode of ownership including
trade name as registered in the Department of Trade.
A list of changes in transmitting facilities (arranged chronologically). Annex to this list, the corresponding licenses and permits supporting the changes.
Copies of the Program Standards, the Technical Standards, the NTC compilation of laws, regulations, circulars and memoranda.
Evidence of membership in the KBP.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
ECE ELECTIVE III
BROADCAST ENGINEERING AND ACOUSTICS
Introduction to FM Broadcasting System
and Standards
Frequency Modulation (FM)Frequency Modulation The process of varying the frequency of a
high-frequency carrier wave in accordance with the amplitude variations of the modulating signal.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Uses of FM
1. FM broadcast (88 – 108 MHz)
2. Television sound
3. Satellite Television (both audio and video)
4. Mobile radio services
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
FM Broadcasting Standards (FCC)Frequency allocation: 88 to 108 MHz divided into 100 channelsChannel spacing: 200 kHzPermitted channel bandwidth: 200 kHz (±75 kHz deviation for maximum modulating frequency of 15 kHz, and a 25 kHz guard band on both sides)Type of emission: F3E (monoaural) F8E (stereophonic)Intermediate Frequency: 10.7 MHz (10.61 to 10.79 MHz)Pilot Subcarrier Frequency: 19 kHz
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Classes of FM StationsClass-A Shall have an authorized transmitter power not
exceeding 25 kW and an ERP not exceeding 125 kW. Minimum transmitter power is 10 kW
Class-B Shall have an authorized transmitter power not
exceeding 10 kW and an ERP not exceeding 30 kW. Minimum transmitter power is 1 kW
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Classes of FM Stations
Class-C A non-commercial, community station having an ERP
not exceeding 1 kW Class-D Shall have an authorized transmitter power not
exceeding 10 W. Used for educational purposes.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
FM Antennas and Site Considerations The antenna used in FM broadcasting is
a half-wave dipole.
The transmitting antenna location should be chosen so that line-of-sight can be obtained from the antenna over the general service area.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
FM Antennas and Site Considerations To provide LOS within the principal area,
the antenna must be conveniently above the average terrain.
A tower, elevated structures (buildings) can be used to elevate the antenna
Hills and mountains can also act as natural towers.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Pre-emphasis and De-emphasis Since noise sideband power in FM decreases
inversely with the modulating frequency, higher modulating frequencies are more susceptible to noise than the lower ones.
A method of artificially boosting the affected frequencies with respect to a pre-arranged curve before transmission to improve noise immunity is termed as pre-emphasis.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Pre-emphasis and De-emphasis The compensation at receiver side is
called de-emphasis
The amount of pre/de-emphasis for FM broadcasting has been standardized as 75μs
In the UK, the amount of emphasis is standardized to 50μs
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Stereophonic FMStereo (also stereoscope)
Originally referred to a special photographic technique used to give the viewer the impression of observing a scene in three dimensions
In stereophonic audio, a sound source is recorded
from two different angles (in this case, the left and right sides). During playback, these signals simulate the sound to the left and right ears, giving the illusion of a three-dimensional sound source.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Problems encountered with initial design ofstereophonic FM broadcasts:
1. Original FM broadcasts were monophonic. The system should be compatible with existing monophonic receivers
2. The stereo information had to be transmitted within the 200 kHz bandwidth allotment
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Block Diagram of a Stereophonic Transmission System
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Spectrum of a Stereo FM Multiplex System
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Some notes on FM Stereo
1. Why are the L & R signals not sent independently and simultaneously? So that the system will be compatible with existing
monoaural receivers 2. What’s the use of the 38 kHz subcarrier? To serve as the carrier for the balance modulation
process of the difference signal
3. Why 38 kHz? The difference signal must not interfere with the
original sum signals
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Some notes on FM Stereo4. Why suppress the 38 kHz subcarrier? Too much of the total composite modulating signal would
be taken up by the subcarrier voltage
5. What’s with the 19 kHz pilot subcarrier? It is used as the reference to obtain the difference signal. 6. Why 19 kHz? Most people cannot hear beyond 15 kHz, much more 19
kHz.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Subsidiary Communications Authorization (SCA)
The transmission of programs which are
of a broadcast nature, but which are of interest primarily to limited segments of the public wishing to subscribe thereto.
Uses a subcarrier of 67 kHz and is modulated to a depth of 7.5 kHz
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Typical applications of SCA1. Background music, weather, time signals2. Educational information3. Talk-back for remote stations4. Telemetry5. Facsimile6. Slow-scan TV
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
The Broadcast Studio The studio usually contains equipment
for program origination.
It is a usual practice to co-locate the studio and transmitter in a single facility, mostly for economic purposes.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS
Remote Studio Facilities In cases where the studio and the
transmitter cannot be located in the same facility, or it is better for the transmitter to be located elsewhere (economically or technically), then a studio-to-transmitter link (STL) may be employed.
ECE ELECTIVE IIIBROADCAST ENGINEERING AND ACOUSTICS