Broadcast engineering - a field of study that covers the design and implementation of procedures, devices and structures for the production of programs and its subsequent transmission to the general public using electronic means

Broadcast - to cast out in all directions

Major fields of broadcasting:

AM

FM

TV

international

* Internet Broadcast

Parts of a broadcast day:

daytime - local sunrise to local sunset

nighttime - local sunsetto local sunrise

experimental - midnight to local sunrise

AM Broadcast:

Freq band - 535(525)-1605 kHz

BW per channel - 30kHz

Center freq spacing - 10kHz

No. of channels - 106

center freq tolerance - 20 Hz

A3E emission

first channel fc - 540 Khz

operating power - 50 Khz max

- must be 3 channels apart

- single omnidirectional or multielement vertical antennas

- antennas are generally erected on flat grounds

Braodcast Service areas:

primary - no co-channel interference and fading

secondary - no co-channel interference, with fading

intermittent - with co-channel interference and fading

FM Broadcast:

Freq band - 88-108 MHz

BW per channel - 200kHz

Center freq spacing - 200kHz

No. of channels - 100

center freq tolerance - 2kHz

F3E (mono)/F8E (stereo) emission

first channel fc - 88.1 MHz

operating power - Class A: 100-3k W erp, 300ft antenna ht,

Class B: 5-50 kW erp, 500ft antenna ht

Class C: 25-100 kW erp, 2000ft antenna ht, 10W educational stations

- the greater the power, the further away in mikes and in freq must the stations be

- single community service

- antennas mounted on high buildings or peak; horizontally polarized

International (AM) Broadcast

- 9 bands: 6, 7, 9, 11, 13, 15, 17, 21, 26 MHz

- 50-500kW power output

- directional antenna of 10 dB gain

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Components of a Broadcast Station:

combo operator - plays music and takes care of the tx

auxiliary tx - for emergency use/EBS xmsn

alternate tx - operates 24 hrs

master audio console - for mixing and switching feeds

gain controls - attenuators, faders, pots (potentiometers); amplitude of the program can be varied

- above 85% below 100% mod on negative peaks

remote pick-up bc station - base statiobn located at the bc station control point; communicates with the mobile pickup bc station

aural bc stl station* - fixed station that broadcasts programs material fromstudio to tx radio link

aural bc intercity relay station* - transmit program material between different cities

*500kHz channel, no more than 200kHz FM, directional antennas

Broadcast Console: nerve center of a bc station

- control point, switchboard

- a complicated group of amps, switches, relays and gain controls

S switch

P program position

A audition

VU meter - visual indication of the signal strength

station break - station ID

talk back - intercom; between the operator and the people in the studio; operator can hear anyone speaking in the studio

- used to notify a studio that is about to go on air

on-the-air - red light in the studio notif

G1-G5 channel gain controls

G6 program master gain

G7 monitor gain

G8 audition master

Broadcast station requirements:

timing

fidelity - no distortion to the program

% mod - maintaining proper console signal output (85-100%)

Audio levels: expressed in volume units (VU)

- the more amplificatio following the gain control, the more noise is amplified

notes:

Telemetering in BC satations is used from remote position to tx

3 ways programs received in bc stations:

telephone lines

radio relay

satellite

BC station must be identified at least once an hour

Important Equipment in a BC Station:

peak limiting amp

equalizer

attenuator pads

Line equalizers: volume control to certain freq

Peak limiting amplifiers: limits high audio peaks to prevent overmodulation

Attenuator pads: used to terminate amplifiers feeding long xmsn lines to tx equipment for less distortion by the ampli

T pad - used as voltage dividers ; variable attenuator ; unbalanced ground, equal R

H pad - voltage divider ; balanced ground, equal Z

U pad - unequal Z, balanced ground

L pad - unbalanced ground, unequal Z

reasons for using: loss decibels, match z values and center tap lines

Classification of BC Station Powers:

MRCP - maximum rated carrier power ; max power tx can be operated ; must be equal or exceeding the licensed power

Licensed/Authorized operating power - fed to the antenna by the tx ; tolerance 5% above or 10% below

PIP - plate input power = IpVp

operating power Po

-direct method Po =Ia2 RaAM bc station

-indirect method Po = IpVpFFM bc station and TV aural tx; AM in emergencies

BC Station Tests:

equipment test- between mn and local sunrise (experimental period)

service/program test - testing the station on air

equipment performance test - annual test for am bc stations ; harmonic content, carrier amp regulation, hum & spurious rads

- annual test for fm bc stations over 10 W

proof of performance test - annual tesst of the antenna rad pattern of any directional array; antenna fielld strengths

notes:

If antenna ammeter burn out, it must be replaced within 60 days

ATS - automatic transmission system

Record-Playback Equipment:

tape record-play mechanisms:

a.open reel - when capstan is forced against the tape and the rotatable idler post, the tape is pulled along toward the take-up reel

b.cassette - smaller reels are enclosed in a plastic case

c.cartridge - uses endless tape and only one reel

Turntables - made of cast aluminum and belt rim, driven by synchronous motor

pickup heads - tone arms ; magnetic with long-play diamond styli (needles)

Microphones:

dynamic

velocity

condenser

- when 2 or more mics are used, the phase of their connections may have to be reversed

Emergency Broadcast System (EBS) - formed on voluntary basis by certain bc stations during emergency

emergency action notification - ean ; a two-tone attention signal (853 and 960 Hz) for 23s, followed by the announcement

emergency action terminiation - eat ; at the end of the emergency

EBS levels:

1.national - primary stations

2.state/region - primary relay station

3.local cpcs - common program control stationa

EBS message priority:

1.presedential

2.local

3.state/regional

4.national

emergency action condition - eac

Station Logs:

- lisitng of the date and time of events, programs, equipment parameters, tests etc

- either braodcast day or 24 hrs

- minor corrections may be made before logging the meter reading

- errors should not be erased; they are lined out, corrected above the error

program log - signed by the operator ; sign on/off, prog sked + details

operating log - signed on and off watch ; entries of operatring parameters, tx sked details, antenna sked details etc

maintenance log - preventive maintenance or breakdown maintenance

FM Stereo Multiplex:

- FCC authorized compatible system of stereophonic fm bc

stereo - making sounds 2d to listeners

Stereo Multiplex Receivers:

Quadrature amplitude modulation - QAM

Compatible quadrature amplitude modulation - CQUAM ; AM stereo experiment

SCA and Quadraphonic:

sca - subsidiary communication authorization

- transmit background music etc. from remotes to control

- transmit encoded alphanumeric news to fax machines using digital techniques

Quadrophonic system - 4 signals to 4 speakers

F (L+R) - 0-15KHz

F (L-R) - 23-53KHz

R (L+R) - 23-53KHz

R (L-R) - SCA

surround - after quad ; 5.1 base speaker

Antenna Towers:

- painted with equal-width stripes

- aviation orange TT-P-59 ; aviation white TT-P-102

- stripe 1/7th ht of the tower

- bottom and top must be orange

- tower light inspection once a day

- 3 mos interval inspection of control devices, indicators, malfunctioned alarm systems

15oft towers - steady burning 116 or 125 W (32.5 candela) lamp for night mark ; aviation red light globe at the top ; 35 foot candles sky luminance

higher than 15oft - 620 or 700 W PS-40 Flashing Code Beacon lamps ; 2k candela ; aviation red filters

- report failed lights to FAA Federal Aviation Administration within 30mins

Presunrise Service Authority - bc staions with 500 W or less operating power ; operate between 6am and local sunrise