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A Tunnel Diode Keyer (at last!)

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Hi Folks,

I've had an idea that it might be possible to build an electronic Morse keyer using tunnel-diodes since I first read about them as a kid. Several early attempts were unsatisfactory, to say the least. Fast-forward forty years: While taking a shower last month a design possibility popped into my head "out of the blue." Unlike most of my "brilliant" ideas this one actually worked on the breadboard ;-)   

I'm using the classic, W9TO keyer configuration in which an astable multivibrator is followed by a pair of bistable flip-flops (FFs) connected in series. The combined (OR'd) FF outputs comprise the dashes. In my circuit a tunnel-diode relaxation oscillator feeds a pair of tunnel-diode bistable FFs. My recent revelation involves gating the FFs with biased signal diodes. The attached oscilloscope screen-capture shows the DOT/DASH output waveforms.

I made the first QSOs on 20m the other day with my new keyer. While it has no "bells and whistles" (no dot/dash memories, iambic operation, etc.) it does send very tolerable CW. I realize that an electronic keyer made from five Soviet-made tunnel diodes is "small potatoes" in a day of full-functioned keyers on a chip, but for me it was a childhood dream finally come true. I'm presently working on a magazine construction article, but for now I just wanted to share my news.

Happy Holidays,
Mike, AA1TJ

Many thanks, Mike, for your sharing!

72 de

Prego, Nicola...you're very welcome.

Mike, AA1TJ

Have you a schematic ? Sounds interesting,and I would like to build the circuit just for the fun of it.

Carl  AA2JZ

Good contribution Mike. Many tnx!


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