I designed and built an analog varactor-based Colpitts VFO for the 20m ham radio band. It鈥檚 built around two BB910 diodes, a 10-turn pot, and two J310 JFETs. Has some warm up drift but is very stable after a few minutes. It was designed to use caps I already had. Very happy with this!
I used c0g caps and elevated the toroid and trimmer to keep heat away from them. Advice is to use air core here but the toroid takes less space. Note I removed the unnecessary heat sink.
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