The best diode type for a crystal set?
Posted: Wed Jan 29, 2025 11:16 pm
I had some fun email with KC4NYK about the best diode for a crystal set.
So, I blew the dust off some old memories and found some new devices to recommend;
So, I blew the dust off some old memories and found some new devices to recommend;
…login to view the rest of this postThe article shows why the OA90 series, the old winner generally thought to be OA91, are popular in crystal sets -very low forward voltage.
http://qrp.gr/ultimatextalset/
But there are many others; maybe someone can tell us about the Marconi detector?
A crystal set tuned circuit, ideally, is a high-Q LC tank operating with available antenna-provided low voltages to provide RF to a simple rectifier demodulator. This rectifier needs to be a lowest forward voltage type, or there is insufficient half-cycle RF to make it conduct to provide an audible output.
Can you forward bias a Si diode? Yes, we bias Si varactors every day to make them work, however the joy of the venerable crystal is its independence from external power? A further design consideration is how to maintain high Q of a L-varactor tank, or LC-to-lower impe