Schematics > RF circuit > VHF Audio Video Transmitter
VHF Audio Video TransmitterThe circuit presented here
is a simple audio/video transmitter with a range of 3 to 5 metres. The A/V signal
source for the circuit may be a VCR, a satellite receiver or a video game etc. A
mixer which also operates as an oscillator at VHF (H) channel 5 TV frequency is
amplitude modulated by video signal and mixed with frequency mo enna, contains video
carrier frequency of 175.25 Mhz and audio carrier frequency of 180.75 Mhz. Then,
the transmitter is a B-System of CCIR compatible.
The circuit consists of transistor Q1 with its resonant tuned
tank circuit formed by inductor L1 and trimmer capacitor VC1, oscillating at VHF
(H) channel 5 frequency. Transistor Q2 with its tuned circuit formed using SIF coil
and inbuilt capacitor forms oscillator. The audio signal applied at the input to
Q2 results into frequency modulation of 5.5 Mhz oscillator signal. The output of
5.5 Mhz FM stage is coupled to the mixer stage through capacitor C8 while the video
signal is coupled to the emitter of Q1 via capacitor C4 and variable resistor Inductor
L1 can be wound on a 3mm core using 24SWG enamelled wire by just giving 4 turns.
Calibration/adjustment of the circuit is also not very difficult. After providing
12V DC power supply to the circuit and tuning your TV set for VHF (H) channel 5
reception, tune trimmer VC1.
Title: VHF Audio Video Transmitter
Source: unknown
Published on: 2005-08-27
Reads: 2236
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