Television Transmitter

TELEVISION TRANSMITTER

A simplified functional block diagram of a television transmitter is shown in Fig. Necessary details of video signal modulation with picture carrier of allotted channel are shown in picture transmitter section of the diagram. Note the inclusion of a dc restorer circuit (DC clamp) before the modulator.

Also note that because of modulation at a relatively low power level, an amplifier is used after the modulated RF amplifier to raise the power level.

Accordingly this amplifier must be a class-B push-pull linear RF amplifier. Both the modulator and power amplifier sections of the transmitter employ specially designed VHF triodes for VHF channels and klystrons in transmitters that operate in UHF channels.

Vestigial Sideband Filter

The modulated output is fed to a filter designed to filter out part of the lower sideband frequencies. As already explained this results in saving of band space.

Antenna

The filter output feeds into a combining network where the output from the FM sound transmitter is added to it.

This network is designed in such a way that while combining, either signal does not interfere with the working of the other transmitter.

A coaxial cable connects the combined output to the antenna system mounted on a high tower situated close to the transmitter.

 A turnstile antenna array is used to radiate equal power in all directions. The antenna is mounted horizontally for better signal to noise ratio