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Thursday, February 4, 2016

A Probable First: First Ever Radio Contact Using Unijunction Transistor as the Transmitter


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

10 comments:

  1. Now you know how Marconi felt!
    Great story.

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  2. This comment has been removed by the author.

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  3. 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?

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    1. 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...

      Delete
  4. Oops, the above post was by AA1TJ

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    1. 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!

      Delete
  5. 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

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  6. 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

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    Replies
    1. 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

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  7. 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

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