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Saturday, March 27, 2010

Polyakov Plus! Dual-band Receiver with Subharmonic Mixer

I found it! SPRAT 110, Spring 2002, page 5. A short article by OM Rudi Burse, DK2RS. This is the variation on the Polyakov Russian Mixer that I mentioned a couple of days ago. I'd been digging through piles of books and old magazines looking for this. My wife thought I'd gone nuts. (Well, nuttier than usual, actually.) It didn't help that I responded "The Polyakov Russian sub-harmonic mixer circuit with two band application!" when she asked what I was looking for. Of course, I should have known that it was in SPRAT. It just happened that the issue with this article was piled under a lot of junk on the workbench. I really like this circuit. Ingenious. And now that I have come to understand mixers a bit better, I can appreciate this one more. Here's how I'd explain it: With the switch closed, the signal from the LO "opens" one of the diodes on the positive peak, and it opens the other diode on the negative peak. So that RF signal from the antenna is getting sampled and mixed twice each cycle of the LO. The resulting complex waveform has sum and difference frequencies of RF+2LO and RF-2LO. With the switch open, you only have one diode sampling the RF, and it opens only ONCE each LO cycle. So the complex waveform that comes out of this single diode had frequencies of RF+LO and RF-LO. This opens the possiblity of DC receivers for 80/40, 40/20, 20/10 meters, etc. I guess a key adjustment in this circuit would be getting the LO level just right. Thanks SPRAT! Thanks Rudi! Thanks Vladimir Polyakov!

You'll see in the comments attached to my last blog post that our man on the left coast, Steve Smith, gave that cute little Doug DeMaw/Vlad Polyakov receiver a name that might set American-Russian hamrelations back a bit: He called it "Vlad The Inhaler." Good one Steve! (But you might want to stay out of the diplo game!) 

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  1. Hi Bill,
    nice circuit indeed - but in the
    low band case, you have only one diode active, which could case some hum problems.
    Why not instead switching D1 switch D2, while eliminating SW1
    in the way, that D1 cathode is switched to ground in the low band mode.
    So far I see, that should give you a more hum-proof mixer similar to the one Mike/AA1TJ uses e.g. in his reggie-project
    ( although Mike uses the shunt-version ) - see
    Just an "outta the blue" idea, don't take it too serious...

  2. Hi Bill,
    sorry mixed up D1 and D2 -
    what I meant was:
    While leaving D2 in the circuit all time, switch the cathode of D1 to ground in the low band mode.
    Thus the positive sinewave of the Lo will be shortened to GND and isolating the input signal from AF, while the negative one will sample the input signal to the AF port.



  3. I'm a bit curious to see if I can get this working on 80/40.

    Which diodes would suit best; 1n4148, 1n34 or 1n60?

    Whats the construction and values of the two inductors, L1 and L2?

    In fact how do I go about calculating the right values, so I don't have to ask how they were constructed?


    Kim VK5FNET

  4. Hi Bill,
    simulated, what I suggested in my earlier comments - don't waste your time: doesn't work, all I tried, keeping the second diode
    active in the low band mode, makes
    everything even worse...,sorry


  5. Even kids know that it work great. There is complete data for every band. So let's look to original soruce: http://www.cqham.ru/prostoy_ppp.htm
    And how does it sound? Yeap very good:

    73 de YT1ZW

  6. You can also see the receiver , vu3inj.blogspot.in


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