Monochrome TV transmission
An over simplified block diagram of a monochrome TV transmitter is shown in Fig . The functional block diagram can be broadly divided into two sections, viz. an amplitude modulated transmitter and a frequency modulated transmitter. Former is used for video modulation, whereas latter is used for audio modulation.
The synchronising and scanning circuits produce sets of pulses for providing synchronising pulses for proper functioning of the TV system. This timing unit contains number of wave generating and wave shaping circuits. The repetition rate of its various output pulse trains is controlled by a frequency stabilised master oscillator.
The output signal of a camera tube corresponding to the image to be televised is amplified through a number of video amplifier stages.
The image signals together with the synchronising and blanking pulses are raised to a level suitable for modulating the RF carrier wave generated in the RF channel. The allotted picture carrier frequency is generated by the crystal controlled oscillator. The continuous wave output is given large amplification before feeding to the power amplifier. In the modulator, its amplitude is made to vary in accordance with the modulating signal received from the modulating amplifier.
The microphone converts the sound associated with the picture being televised into proportionate electrical signal. The audio signal from the microphone after amplification is frequency modulated, employing the assigned carrier frequency. The output of the sound FM transmitter is finally combined with the AM picture transmitter output, through a combining network and fed to a common antenna for radiation of energy in the form of electromagnetic waves.
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