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:
http://soldersmoke.blogspot.com/search?q=tunnel+diodes

They are back at it!

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

Grüss Peter!

Thanks for the nice message. Yes, I knew that you were going to be QRV with your ZnO transceiver but I never heard if you had made any contacts. I guessed that you had not, otherwise I'm sure you would have let me know. 

Again, I think your circuit looks really great! It's amazing to think you managed to squeeze 500uW from a scrap of oxidized zinc-plated steel. Even if you didn't make a contact, what you are doing is really fantastic. Congratulations on the creation of this amazing radio!

Okay, so I spent most of the afternoon at the workbench. Thus far I'm only using a single SRD (step-recovery-diode...1N5401 rectifier). Of course the result is a unipolar pulse. The idea did work as planned, however the power only increased by 2.24dB. The maximum RF output power is now 230uW. At least the SRD makes a pretty pulse :-)   

Please find two scope captures attached to this message. The first (0002) shows the SRD generated unipolar pulse. As you can see, the pulse width is nearly perfect for the job. The second trace shows the output RF waveform. The worst spurious energy is ~20dBc. The second image shows the 507kHz waveform at the unijunction emitter along with the output RF waveform.

The beacon is presently off the air, but I look forward to trying my luck tomorrow with a back-to-back pair of SRDs. A bipolar pulse pair will provide a shock impulse once every 3.5 cycles, instead of once every 7 cycles with the present unipolar drive pulse. The bipolar pulse pair should result in increased RF output power as well as a slight spectral improvement.

It's only a matter of time before you make a ZnO QSO, Peter. As we always say, the difficulty merely sweetens the eventual success. 

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.

73,

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

http://www.sparkbangbuzz.com/els/zincosc-el.htm

and

http://sparkbangbuzz.com/zinc-osc-2/zinc-osc3.htm

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 experimentshttp://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...

73!

Peter/DL3PB

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