LOW POWER TV TRANSMITTER(LPT)

B. SIVA RAMA KRISHNA (08P31A0410)

DEPARTMENT OF ECE SAI ADITYA INSISTUTE OF SCI.&TECH. SURAMPALEM

BY

LOW POWER TV TRANSMITTER(LPT)

Transmitted Power =100W -500W .Coverage distance = around 21kms.Location : Kakinada

HISTORY OF DOORDARSHAN

Beginning: 15 September 1959 with a small transmitter & a make shaft studio.Extended : up to Bombay & Amritsar in 1972 …….Presently: Doordarshan is transmitting 19 channels (i) 2-all India channels (DD National, DD news) (ii) 11-Regional language satellite channels (RLSC) (iii) Four state networks (SN) (iv) an international channel , Sports channel (v) 2-channels (DD-RS & DD-LS)

ANNIVERSARY: Doordarshan celebrated 50 th anniversary in 2009

BLOCK SCHEMATIC OF LPT

SECTIONS OF LPT

MONITORING RACK

Wave form Generator : used to see the signal levels according to the frames of the picture. (like CRO used).

at the rack another device which is used to give the waveforms on television screen (as like dots ,blue back) during after the mid night….

TV: A TV is used to observe the channels after demodulation process.

RECEIVING RACK

Receiver 1, Receiver 2,Receiver 3: receiving the signals from PDA .The receiver no. depends on the regulations given by the DD - Delhi.

Based upon the channels will be decode and transmitted by increasing the power of the signals (so ,it is called as relay station).

V.C.R(Video Cassette Recorder): When there is a news is wanted to telecast at the relay station ,not going to the main centre then it is useful.

TRANSMITTER RACK

Audio-video Switcher: The switch which is used to separate the audio& video.

EXCITER : The audio and video outputs from audio-video switcher unit are fed to exciter unit. The audio input is fed directly to the aural modulator while the video signal is passed through a low pass filter before being fed to its respective modulator.

Driver amplifier : consists of class-A power amplifier .it contains two similar 60W power amplifier modules. The power amplifier which is going increase the Power level.

DIVIDER: The divider divides the signal into multiple parts.

COMBINERS : The combiner is used the sum up the power levels of power amplifiers, then the power will be increased.Transmitters used: VHF is used for CH11,UHF is CH33.After the signal boost up then it send by using Mast antenna .

OTHERS IN THE LPT

Parabolic Dish Antenna (PDA) Size : very small(ku-band).

Generator power supply: The generator generates 35KVA power supply.Mast antenna : after reception & strengthening is over then it is send By using Mast antenna (tower antenna) it is send by using horizontal propagation.

BANDS & RECEIVING SECTION

L 1-2Ghz.S 2-4Ghz. C 4-8Ghz.X 8-12Ghz.KU 12-18Ghz.

• Look angle :view related to east or west•Azimuthal angle =(0-180 degrees) horizontally•Elevation angle = (0-90 degrees) vertically•Latitudes and longitudes

VHF TRANSMITTERS

Freuency range :224 MHz-231MHz

UHF TRANSMITTERSFrequency :564-574MHz

manufactured BY Bharat Electronics Limited (BEL)

UHF TRANSMITTERLinearity corrector:function is to correct the non-linearity’s that occur in power amplifiers operated in this band

Up- convertor:The up-convertor unit combines modulated vision IF an aural IF signals and translates to respective channels frequency suitable for transmissionSplitter:The linearity corrector output is dividing into four equal amplitude and phase outputs to fed four PA to get the required output power

Combiner:

Two way combiner is used to combine the outputs of four amplifiers.

TYPES OF MAST

Self supporting mast: The antenna is at the top of the mast and it is used send the signals without any obstacles.

Guided mast : mast is suspended from the ground and it is supported by some wires so that it would with stand to the climatic conditions.

CONCLUSION

I learned how the tv transmission occurs are learned by various sections like monitoring rack transmitting rack input rack.