Download - Broadcast Stations Reviewer
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