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ALTOIDS Tin FM Transmitter


Hello home builders, no breakthrough technology here, just a repackaging of the famous Veronica 1 watt VCO FM transmitter. There are minor part and schematic changes, but it's only a home built clone. This design uses regulated 12 vdc to the oscilator and amplifier stages, maximum power is .6 watt but then fan cooling is required. I run the unit at a reduced output power of .25 watt, without a fan and get virtually no drift in frequency after warmup.



The Veronica 1 watt VCO kit
The Veronica 1 watt VCO kit

Circuit Description: The transmitter uses 2 MPSH10 (equiv to BF494 or NTE229) transistors in a double-ended free-running voltage controlled oscillator (VCO) operating at half the output frequency on each side. The amplifier stage is a MRF515 (equiv to 2N4427 or NTE346) operating in class C, tuned to the 2nd harmonic of the VCO and amplified up to .6 watt in the 88-108 MHz range. The mono audio input circuit is totally passive with 70us pre-emphasis provided and the audio quality is great.



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the schematic

"part 15 version"

The schematic and how to build information is derived from
The Norwegian Radio Pirate League's artical titled "The VERONICA"

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ALTOIDS Tin FM Transmitter

The unit is constructed with copper clad board, a large piece is used as the construction surface and is soldered into the tin. Other board material is cut into small pads, then glued to the construction surface for part connections. A small heatsink is needed for the amplifier transistor, this can be made from tubing with a slot cut into it, then slid over the transistor. In order to make the transmitter operate properly, it needs to be tuned. Set all the trimmer capacitors to middle position (except c2, set it to minimum), connect the rf out to a wattmeter/dummy antenna and apply power. Adjust c1 for desired frequency, then c3 and c4 for max power. C2 acts like a power adjust control, don't adjust for more then 250mw without additional cooling.



- DJ Pirate Joe



ALTOIDS Tin 3.5 watt FM amplifier Click Here

ALTOIDS Tin Part 15 Version FM Transmitter Click Here

Stereo ALTOIDS System Click Here



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