AA1TJ writes:
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.
Wikipedia on Unijunction Transistors: https://en.wikipedia.org/wiki/Unijunction_transistor
Now you know how Marconi felt! Great story.
K1SWL reports that my (95km distant) signal climbed out of the noise to peak at S-9 for a period lasting several seconds, after which it fell back into the noise. W1PID (112km) witnessed the same event, but with a less dramatic peak signal level. I’m admit to knowing little-to-nothing about 80m propagation. Meteor trail reflection? Hovering alien Mothership? …although I allow there may be a more mundane explanation for this dramatic, sudden path enhancement. Ideas?
Oops, the above post was by AA1TJ
Damn it, you pulled it off before me! I never got the output of the UJT with 160m crystal without a lot of noise… Gave up on it a long time ago, after you sent a PCT 🙂 Didn’t have my ticket back than, the worst part I’ve got it over 2 years now… And didn’t make a single QSO yet. Besides messing around point-point with B-K oscillators on 70 and 13cm. A 1-triode, 2-transistor 13cm band RX running on 9V! Or pentodes used as klystrons, very easy to do. But how did you do it? You got any schematic? By coincidence I was looking at the UJT again, thinking about how to make a electronic PCT-equivalent. But quickly dropped it for the an Enhacement Mode MOSFET, with the Gate made very leaky with resistors. Congrats! 73, ON4CPT/Thomas
Ow by the way, what type of UJT are you using? And got any idea on the waveform? Yes a lot of questions, but this caught my fascination!
Well, I know not much about 80m propagation either, but it seems like it must have been quite a localized event, that caused the peak? Since 17km away the effect was a lot less strong..? Theoretically seen, aircraft doe produce reflections at such low frequencies. If you look at Chain Home, ran originally on 6 MHz… Just a suggestion… Never heard of any aircraft scatter at 80 meters! But, it is possible at the right angle/altitude etc it worked as a reflector…
Hello Thomas, Tnx OM. It’s wonderful to hear from you! I think we have much to discuss 😉 I’ll send you an email (provided you have the same Gmail account). 73/72, Mike, AA1TJ
I was pleased to have added five more unijunction QSOs to my logbook last evening. My best DX thus far (AA1MY/Maine) is 161km. Cheers, Mike, AA1TJ
Yes I still have my Gmail adress, linked to this account now. Haven’t used it in ages tough. This is the account linked to my email-adres. Not really running anything solid-state involved right now, neither HF. Just the triodes running as a B-K oscillator, another negative resistance device 🙂 UHF/microwave transmitter consisting of a triode, 4 RFCs and some form of antenna. Don’t get much simpler 😉 Now gotta go, Looking forward to hear from your succes with the UJT! 73, Thomas, ON4CPT