1. Training at Doordarshan kochi

2. History A Public Service Broadcaster largest terrestrial television network in the world Service started in New Delhi on 15 September 1959 Regular daily transmission started in 1965 National telecasts were introduced in 1982

3. Doordarshan in Kerala Number of studios : 3 Transmitters can high power transmitter or low power transmitters. video audio

4. HPT : vision and sound carriers can be generated, modulated and amplified separately, combined in the diplexer at the transmitter output. LPT sound and vision are modulated separately but amplified jointly DD cochin-HPT HPT-7 LPT-22 Satellite : INSAT-2E INSAT-3A INSAT-3E PAS-10 INSAT-3C Position : 83 ° E 93.5 ° E55 ° E 68.5  E 74 ° E Transmission in VHF I and III band(40-68MHz &174-230MHz) UHF IV and V band(470-606MHz&606-798MHz)

5. Studio Origin of a programme Programme are live or recorded or from OB spot Programmes from studio to transmitting centre through broadcast quality telephone lines or studio transmitter microwave/VHF links Size 20mx20mx8.5m

6. Requirements Camera Audio system Lights Key light Fill light Back light Audio Video connector Flooring: marblex is provided Walls:Ivory finished celotex surface Cyclorama: to avoid unnecessary reflections Air condition,Safety measures etc..

7. Lens area Central apparatus room Generate Colour composite video signal Production control room audio console : to which microhone connects video console : control lighting camera control unit : controls camera Producer Mic controller Floor manager

8. VIDEO STANDARDS 3 standards - NTSC National Television Standards Committee 1 frame = 525 horizontal scan lines -PAL Phase Alternate Line (PAL) 1 frame = 625 horizontal scan lines -SECAM Sequential Color and Memory 1 frame = 625 horizontal scan lines

9. TV Transmission Audio signal Acoustic vibration converts to signal by lapel or condensor microhone. Frequency modulation and line of sight propogation Audio carrier frequency : 229.75MHz Video signal Light converts to electrical signal by charge coupled device. AM and ground wave propogation Video carrier frequency : 224.25MHz

10. VESTIGIAL SIDE BAND TRANSMISSION Normal amplitude modulation require 11 MHz bandwidth limit the number of channels in the spectrum allotted for TV Part of lower side band +upper side band=5.75 MHz COLOUR COMPOSITE VIDEO SIGNAL (CCVS)

11. TYPES OF MODULATION Positive modulation : Picture brightness is directly propotional to amplitude Negative modulation : inversely propotional max amplitude for sync min amplitude for white ADVANTAGE OF NEGATIVE MODULATION No noise affect video signal Better transmitter efficiency Provide a reference for AGC in receiver

12. HIGH POWER TRANSMITTER Exciter amplifier Diplexer Exciter amplifier Diplexer

13. Description DD news & DD 1 programmes Two transmitters 1) Rohde & Schwarz For DD1 German made,costly Software controlled Liquid cooling Coolant:Antifrogent 6 Amplifiers : 5 for video, 1 for audio

16. 2) NEC For DD news Japan made Digitally controlled Air cooling : consume high power and noisy 12 Amplifiers : 10 for video,2 for audio

18. EXCITER (SH700) Heart of transmitter Avoid nonlinearity of amplifier Encoder for analog TV I/Q Modulator Synthesizer Central control unit Power supply

20. AMPLIFIER Class B Pushpull amplifier Microwatt power convets to kilowatt power DIPLEXER Band pass filter Mix audio and video signals Rigid copper cable : to connect diplexer outut to antenna Dehydrator : to keep dielectric constant of air 1 Antenna : dipole,130m,1000 sq km Total antenna : 32

21. Direct to Home Receives signal from 4 transponder. C band and Ku band signals are received. Convert to L band for further processing A transonder carry 14 channels Integrated receiver decoder decodes programmes

22. CONCLUSION Doordarshan is a Public Service Broadcaster and among the largest terrestrial television network in the world. Doordarshan cochin is a high power transmitter.It mainly receives the programmes from Delhi and Trivandrum through satellite INSAT 3A&4B, Mainly DD cochin broadcast DD1 and DD news.The two types of transmitters that are in use are Rohde and Schwarz which is for DD1 and NEC for DD news.The antenna here is a dipole antenna and total number of antenna is 32.