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Small 2M crystal FM design
Hi, I'm looking for a small, 2m FM fixed frequency TX design for a
backup telemetry link on a model craft. I've seen designs based on discontinued Motorolla baby-monitor ICs, but simple varactor/tripler designs seem less common. Weight/size are important, and I'd like output around 1-2W. Duty cycle will be fairly low. There is 4.8V or 12V available already; 4.8V is likely to be noisier, as it drives the servos. 12V is prefered. What I was thinking was ~48 Mhz crystal oscillator with varactor, fed into a tripler, then a bandpass, then into an amplifier (RF transistor?)? I've seen a number oscillator designs floating around (handbook and otherwise), but I don't know how to find out what's most appropriate. Any suggestions, designs I've missed, books to read, etc? Something like the Ramsey FM6 (preraid)? Plan B is to find another HTX-200 or similar, pull out the guts, and use that. :) But I'd rather have something I can lay out myself. Thanks, R C KG4MVB |
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