rajkot

Thursday, February 4, 2010

T.V.TRANSMMITER CIRCUIT


  • Here, uses FM modulation for sound and PAL for video modulation.
  • The audio signal to be modulated is pre-amplified using the transistor Q1 and associated components.
  • The transistor Q2 has two jobs: production of carrier frequency and modulation.
  • The pre-amplified audio signal is fed to the base of transistor Q2 for modulation. Capacitor C5 and inductor L1 forms the tank circuit which is responsible for producing the carrier frequency.
  • The video signal is fed to the emitter of transistor Q2 via POT R7 for modulation. The modulated composite signal (audio+video) is transmitted by the antenna A1.

  • NOTES:
  • Assemble the circuit on a good quality PCB.
  • Inductor L1 can be made by making 4 turns of 24SWG enameled copper wire on a 6mm dia: plastic former.
  • T1 can be a radio frequency transformer with built in capacitor. (Can be found on old transistor radio boards).
  • Antenna A1 can be a 1M long copper wire. (Experiment with the length to get optimum performance).
  • This transmitter is working in VHF band somewhat between 50 – 210MHz.
  • This transmitter is compatible only with PAL B and PAL G systems.

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