Laboratory Manual for
Faculty of Technology
Dharmsinh Desai University
TABLE OF CONTENTS
Monochrome and colour television receiver block diagram.
To Trapezoidal Waveform Generation (15625 Hz).
To study Sync separator circuit.
To study Pattern generator.
To study Vectroscope.
A) To study Composite video signal.
B) To Study Colour signal
To study RF Section (Tuner).
RF section Fault finding by simulation of faults.
To study details of VIF section through test points.
VIF section Fault finding by simulation of faults.
To study Chroma section and faults in chroma section.
To study fault finding in monochrome television receiver.
Monochrome and Color Television Receiver
AIM: To Study The Monochrome Television Receiver and Colour Television Receiver. APPARTUS: A Monochrome and Colour Television Receiver.
Block diagram of Monochrome Television Receiver and colour television receiver: THEORY:
A Monochrome Television Receiver Consists of the following functional sections which will be studied and explained as:
Input from Antennas:
Strongest signal is induced in the antenna if it has same polarization as the transmitting antenna. All TV antennas are mounted in horizontal position for better reception and favorable signal to noise ratio. A yogi antenna, i.e. a dipole with one reflector and two or more directors, is a compact high gain directional array, and is often used in fringe areas. In areas where signal strength is very low, booster amplifiers with suitable matching network are used. on the other hand, in areas situated close to a transmitting antenna, where signal strength is quite high, various types of indoor antennas are frequently employed.
This section consists of rf amplifiers, mixer and local oscillator and is normally mounted on a separate sub-chassis, called the “front end” or “RF tuner”. The purpose of tuner unit to amplify both sound and picture signals up by antennas and to convert the carrier frequencies and associated side band into intermediate frequencies and sidebands. In principle and RF amplifier is not necessary and signal could be fed directly to the tuned input circuit of the mixture. However, the problems of (1) a relatively weak input signal with low signal to noise ratio,(2)local oscillator radiation and (3) image tuning for different frequencies of associated tuned circuits by varying either inductances or capacitances of these circuits
The block diagram of VHF tuner is shown in figure. The signal to the tuned RF amplifier is fed through a balun i.e. matching transformer. It is important to note that in a super heterodyne circuit as employed in tuner, mixer is the main source if noise which produces snow on the picture. Therefore, it is necessary that the RF amplifier must function as a low noise amplifier. In the shown figure channel selector switch has been set for channel 4(band 1),i.e 61 to 68 MHz
B. UHF tuner:
The UHF tuner performs the same function as a VHF tuner does, but its design is different on account of ultra-high frequencies in the band. In earlier mechanically tuned versions there is no RF amplifier an the antenna signal on selection feeds into a high frequency diode which acts as a mixer to convert UHF signals to IF band. However, the IF output is not fed direct to the IF subsystem but instead routed via the VHF tuner which is switched to perform to a one or two stage IF amplifier when UHF tuner is in operation.
3. IF Subsystems:
The IF subsystem includes IF section,...
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