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Re: Dual detection in weakly oscillating mode?

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  • sean
    I now think the answer is to put the rf signal from the weakly oscillating regenerative receiver through a high gain amplifier to get it into square wave form.
    Message 1 of 15 , Jan 1, 2011
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      I now think the answer is to put the rf signal from the weakly oscillating regenerative receiver through a high gain amplifier to get it into square wave form. This square wave is pulse width modulated by any signals that are received and can be recovered by averaging with an RC filter. I have posted a new circuit that can do that at:
      http://code.google.com/p/lemontree/downloads/list

      I think the original circuit I posted was doing that by accident rather than by design, or it could have been exhibiting an 'Exalted Carrier' effect (which is a term well worth searching on).
    • Hue Miller
      For some reason, I recalled that I had years ago repaired a WW2 US Army transmitter-receiver, model BC-474. Some previous owner had hooked the B- right to the
      Message 2 of 15 , Jan 1, 2011
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        For some reason, I recalled that I had years ago repaired a WW2 US Army transmitter-receiver,
        model BC-474. Some previous owner had hooked the B- right to the chassis, not thru the resistor-
        to-ground bias network, and so toasted ( burned out ) the output transformer. I used a
        replacement transformer from the SCR-274 series. The impedances worked out right and it
        functioned BUT with fringe howl, which I addressed with the usual de-Q resistor of some
        tens of k-ohms across the transformer primary. Note, the tube was the pentode section
        of 3A8 and it is purely audio amplifier, not a regenerative stage. More grist for the mill.
        -Hue Miller

        [Non-text portions of this message have been removed]
      • Hue Miller
        A follow-up question would be, does this phenomenon only exist in direct-heated, battery type tubes? I have only encountered fringe howl in that one instance
        Message 3 of 15 , Jan 1, 2011
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          A follow-up question would be, does this phenomenon only exist in direct-heated,
          battery type tubes?
          I have only encountered "fringe howl" in that one instance with the NON-regenerative
          PENTODE audio amplifier. But I only have experience with a few regens, the 1960s
          3-tube wonders, the Navy RAL, RBL, and the Torn. E.b sets. - none of which had
          this. -Hue Miller

          [Non-text portions of this message have been removed]
        • sean
          I guess the principle way a regenerative receiver demodulates CW and SSB signals is by pulse width modulation followed by a low pass smoothing. That the
          Message 4 of 15 , Jan 1, 2011
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            I guess the principle way a regenerative receiver demodulates CW and SSB signals is by pulse width modulation followed by a low pass smoothing.
            That the oscillator starts to clip and squares up the waveform. And the squared up waveform is actually pulse width modulated by any CW/SSB signals present. There is one way to test that theory and that is with a Schmitt trigger. That you put the rf output of an oscillating regen through a Schmitt trigger followed by a RC smoothing circuit. If you can still hear CW/SSB signals very clearly then that is proof of concept. Schmitt triggers don't lie. Once the signal is in the digital domain there should be a bunch of tricks you can do.
            I shall busy myself and go buy some Schmitt triggers and solder.
            Thanks, catch you later.
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