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Saturday, January 30, 2016

RESISTANCE IS FUTILE! Diode Tunnels in Germany and Vermont

Peter DL3PB's Zinc Negative Resistance Transceiver

Michael Rainey AA1TJ's work with tunnel diode rigs has provided much grist for the SolderSmoke mill over the years, as has the tunneling of Peter DL3PB:

They are back at it!

Michael updates Peter (and us!) us on his efforts of this week:

GrĂ¼ss Peter!

A broadband measurement of my output power (using an AD8307 log-amp power meter) indicates 139uW. Spurious frequency energy accounts for 2uW, leaving 137uW at 3.552MHz. I believe this is roughly the output power produced by your ZnO transmitter? 

This morning I'll attempt to increase the unijunction (UJT) 80m RF output power by inserting a pair of back-to-back standard-recovery power supply rectifiers (1N5401-ish) at the  UJT base-2 to ground node. Thus far I have relied exclusively on internal UJT nonlinearity for the generation of harmonic energy. I've reason to believe the minority carrier charge-storage capability (normally a defect, but hopefully a virtue here!) of these rectifiers will efficiently produce a bipolar pulse-pair every 1/500kHz seconds resulting in an odd-order comb-spectrum. At least that's the plan...we'll see how it works out ;-)

Peter, I never heard the results of your ZnO DXpedition? Any luck OM?

Okay, I'm off to the Hobbit-Hole. My heartfelt thanks to you all for your shared interest in this cock-eyed project.

Mike, AA1TJ       

Peter, DL3PB, in Germany respond with amazing news of his own.  Peter is homebrewing his own tunnel diodes, using Zinc Negative Resistance Oscillators.  No store-bought appliances for him!
At this point you really have to visit the pages of Nyle K7NS
Nyle tells of building a little microwatt transmitter, and, once the snow melted, climbing a hill 5 miles from town to see if he could hear it.  This reminded me of young Marconi's early efforts in Bologna.

Peter writes:

Hi Folks,

Mike, your plan on how to increase output-power sounds reasonable –  yes, a few dB could really help, to make reception a bit steadier and thus allow a QSO.

Well, I thought we had already talked about the ZnO TRX attempt, but obviously we didn’t. The reason is dead simple - It didn’t work.

[ The ZnO TRX is a minimalist 80m band transceiver with a homemade tunnel-detector-diode as the only active device –  based on Nyle’s K7NS experiments
http://sparkbangbuzz.com/zinc-osc-2/zinc-osc3.htm – please find attached an early schematic ]

Three days in a row after Xmas I tried for several hours each, I had announced the activity on QRPSPOTS and the German QRP Forum. Thus several guys
within the right distance were really trying hard to copy. I used different temporary antennas, mostly verticals, but also a sloper dipole - nada, niente , nothing.
One or two OMs reported weak CW signals on the scheduled QRG, but too deep in the noise, to even make out, whether it was me or someone else.

Yes, power is more or less comparable, actually it’s 0.5mW +/-3dB depending on the day’s form of the homemade tunnel-detector, but I guess all my antennas are
some dB behind a full-size dipole, so at the end it’s pretty much the same.

Folks were very cooperative during the test itself, but after it was clear, that it had not worked, the usual trolls showed up to explain, why that never could have worked...
I plan another test within the coming week e.g. during the PA-contest next weekend ( I’m only 30km from the dutch border ) with a base loaded 15m vertical –
be assured, you’re the first to hear about any success in terms of QSO or just being heard anywhere.

What would we go for, if everything works as expected and/or right from the beginning – or as Jim said it : What fun...


Finally, Alan Wolke provides a very illuminating (as always) explanation of tunnel diodes):


  1. Thanks a lot, Bill, for promoting our microwatt adventures, though in my case it's not yet a story of sucess - could you please on occasion correct my call-sign, it's DL3PB( below the schematic and
    in the introduction ).
    Keep your great blog and the podcast going!

    1. Thanks Peter. Sorry for the errors. I fixed them. 73 Bill

  2. AA1TJ here...

    I spent most of a week working to raise the RF output power from my unijunction transmitter to nearly 1mW. I was rewarded this evening with two contacts.

    Jim/W1PID exchanged (599/449) signal reports with me from Sanbornton, NH (112km) at 2210z!

    Dave/K1SWL did the same (589/229) from Newport, NH (95km) some four minutes later!

    I should think these were the first-ever radio contacts made using a unijunction transistor as the transmitter.

    FYI: my receiver was comprised of a single 1N34a germanium diode mixer followed by a single 2N35 germanium transistor audio amplifier. Great signals on this end.


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