Posted by John Davis on March 07, 2022 at 23:11:13.

In Reply to: Re: Continuous Wave Arcs posted by Ed Holland on March 07, 2022 at 20:58:40.

K7NS wrote elsewhere that he reached 12 MHz with a tunnel diode version of the point contact principle, but the characteristics looked to be so variable that I don't think it is very likely to meet even the relatively loose stability requirements of 22 m. :) All kinds of dissimilar material junctions exhibit semiconductor properties when checked with a curve tracer. Some of the classic crystal detector materials should be especially good, such as galena, silicon carbide, and zincite. (If I recall, the latter is the material Oleg Losev explored at some length.) I've also seen a circuit with a back-biased 1N34 diode that oscillated up into the AM broadcast band, due to negative resistance near the reverse breakdown voltage. I don't know whether one of the modern glass body germanium diodes would work or not, but the older cartridge type 1N21 and 1N34 mil surplus ones would...and there were even a few magazine articles in the late 1948-early 1949 era on how to add another point-contact junction to them to make your own transistor out of such diodes.

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