RGPV Syllabus for Electronics and Communication Branch:

  • TV & RADAR practicals :
Experiment 1.



Objective:
Study of the circuit discription of RF- Section of a Black and White TV (Tuner section)

RF-Section (Tuner section):
The RF-section is mainly consisting of RF tuner. This tuner has RF amplifier, a mixer and a local oscillator.

The anteena receives the radio frequency (RF) waves from the atmosphere and converts them into corresponding signal variations. These RF variations are fed to RF tunner. The input impedance of RF tuner is 75 Ohms. The antenna system and co-axial cable should be properly matched. If a co-axial cable of 75 Ohms impedance is employed , their is no need of any extra matching device between cable and antenna socket at the reciever. But in case of a feeder wire 300 Ohms is employed and then inmpedence matching transformer (300-75 Ohms) is added between feeder and antenna socket at the receiver. Their is also a need of impedance matching between output terminals of antenna and co-xial cable or feeder wire. The RF tuner selects the signal of the desired channel amplifies it and converts in to intermediate frequencies (IF). The video IF is at 38.9 MHz and sound IF is at 33.4 MHz.

Tuner selection has +12V approximately supply voltage at TP6 (MB). This voltage is used for all the operations in this section +12V is provided from horizontal output section. Transistors Q901, Q902, Q903 are used to selecting the desired band from tuner section. To switch on these transistors appoximately 10.8 V is provided at their base. Output is obtained at IF terminals (TP14). AGC voltage (2.8 V approximately) is obtained from pin 11 of IC 8303. This voltage is used for automatic gain controlling purpose. AFT/AFC voltage is provided from pin 18 of IC8303. It is available at TP13. Tuning purpose output from system comtroll IC is fed into the base of transistor Q904 (2369). Which switch on the transistor and so tuning voltage is 0-33V approximately is obtained at TV terminal (TP8).
Following are the various terminal of RF tuner which are provided in the form of tet ponit (TP) in our trainer kit.

BU: The system control IC provides the UHF band selection voltage. This voltage switch ‘On’ the transistor, hence UHF band is selected.

VH: VH band III selection voltage available from system control IC through switching transistor at HB pin.


LV: VHF band I selection voltage available at LB pin from system control IC through switching transistor.

VT: Channel selection voltage is available at this pin through transistor. It is varying from 0-33V during channel selection.

AGC: Automatic Gain Control voltage is available at this pin from IC 8303.

AFT: Automatic Fine Tuning voltage is available at this pin from IC 8303.

MB: It is tuner sections Power Supply pin. Here 12 volts approximately is available.

IF: Intermediate frequency output signal from tuner is available at IF pin.  

Experiment 2.
Objective: 

To Study the Fault Simulation and Step-by-Step Fault Finding Procedure for RF Section.




















































































Experiment 3 

Objective:
To Observe the Horizontal Oscillator section through Various Test Point




Experiments 4



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