How-To: TV modulator from salvage

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In need of a way to transmit a video signal to an aging antennae-input TV set, John rigged up a working RF modulator from salvaged parts (plus 5V supply) –

I decided not to build my modulator from first principles. A simple design with a UHF cavity oscillator and simple sound and vision carrier and modulation circuits is not impossible to make using parts from a scrap TV set, but when so many set top devices already have a modulator built into them why bother? Instead I lifted the RF modulator from a scrap Salora satellite receiver I picked up at a radio rally.
To power this modulator I built a simple 5 volt regulator using the ubiquitous 7805 IC. I simply soldered a TO220 heatsink to the module case and built the circuit around it. My choice of capacitor values was based on those I had to hand. I also included an LED to serve as a pilot light to indicate that the unit was turned on.

You’ve likely come across one of the shiny metal modulators if you’ve ever disassembled a scrapped VCR – read on for more of details of the conversion over @ TechnoToad.

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