Scribd
Upload
602 views2 pages

Monochrome TV Transmission

Video signals from the camera are amplified and sent to the transmitter. Synchronizing pulses control the timing of the system. The horizontal and vertical pulses control the sawtooth generators for deflection, and blanking pulses blank the camera tube during retrace. The carrier frequency is multiplied and modulated by the image and sync signals before a vestigial sideband filter removes part of the lower sideband. The modulated RF energy travels to the transmitting antenna via coaxial cable. An FM transmitter above the video carrier sends the audio signal, and a diplexer combines the picture and sound for transmission by the antenna.

Uploaded by

Sam Dy
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
602 views2 pages

Monochrome TV Transmission

Video signals from the camera are amplified and sent to the transmitter. Synchronizing pulses control the timing of the system. The horizontal and vertical pulses control the sawtooth generators for deflection, and blanking pulses blank the camera tube during retrace. The carrier frequency is multiplied and modulated by the image and sync signals before a vestigial sideband filter removes part of the lower sideband. The modulated RF energy travels to the transmitting antenna via coaxial cable. An FM transmitter above the video carrier sends the audio signal, and a diplexer combines the picture and sound for transmission by the antenna.

Uploaded by

Sam Dy
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
You are on page 1/ 2

Monochrome TV Transmission

Figure shows the simplified block diagram of a television transmitter. The video
signals obtained from camera tube are applied to a number of video amplifier
stages. First stage is located in camera housing to increase weak signal voltage to
such a level as to be transmitted over a coaxial cable to the succeeding amplifier
stages.

Synchronizing generator produces sets of pulses to operate the system at


appropriate timings. This unit includes wave generating and shaping circuits. Eg:
Multivibrator circuit, blocking oscillator circuit and clipping circuits etc. The
repetition rates of the pulse trains are controlled by frequency stabilized master
oscillator.
The horizontal synchronizing pulses are applied to horizontal saw-tooth generator;
vertical synchronizing pulses are applied to vertical deflection saw-tooth generator;
two sets of blanking pulses are applied to control grid of camera tube to blank it
during vertical and horizontal retrace; and a pulse train consisting all above pulse
groups is applied to video-amplifier channel for transmission to receiver.
The carrier frequency generated from a crystal controlled oscillator is passed
through a number of frequency multiplier and amplifier stages. This results in a
production of a carrier wave of desired frequency and energy content. The level of
image signals, together with synchronizing and blanking pulses, is raised to
modulate this carrier frequency. A high level grid modulation is usually employed.
The carrier when amplitude modulated with video signal (BW = 5 MHz) generates
two sidebands and the total bandwidth, required for TV channel would be 10 MHz
which is too large. Therefore vestigial sideband transmission in which one sideband
(say upper) is transmitted in full along with reduced second sideband is used. For
this purpose, output of the final RF amplifier is applied to a vestigial sideband filter
which suppresses the undesired portion of the lower sideband of the modulated
wave.
The modulated RF energy is carried from transmitter to the transmitting antenna by
means of a co-axial transmission line. The antenna elevation is kept high for large
transmission area.

An FM transmitter is used for the purpose of audio signal transmission. The carrier
frequency used in audio modulation is 5.5 MHz above that which is used in audio
modulation. Both, sound and picture signals are transmitted by the same antenna
by using a diplexer called picture sound diplexer.

You might also like