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Regenerative Radios

Discussion in 'Electronic Basics' started by Dave.H, May 26, 2008.

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  1. Dave.H

    Dave.H Guest

    I've been looking for a transistor regen schematic, finally found one,
    but it doesn't give the coil specs. I want to receive the AM band,
    from 530 kHz-1500 kHz. Any help on this very much appreciated.

  2. Dave.H

    Dave.H Guest

    Would A 180 uH or 470 uH choke work as the coil? If not I will have to
    wind my own coil.
  3. Dave.H

    Dave.H Guest

    I found another circuit, that uses a 2N3904, at
    Can I leave the LM386 amplifier out, and could I use a 3.5 inch coil
    form with SWG21 wire? The schematic has two specs for the coil, which
    one is for AM? I'm not good with working with coils, I know how to
    wind them, that's about it.
  4. Dave.H

    Dave.H Guest

    What pins would I connect to on the LM386? I just found one of these
    in my junk box, and want to use it.
  5. Guest


    I have wound many homemade coils that work in the AM range you have
    interest in. There is also a coil calculator. Check out what commonly
    available materials I use at this link.

    Good luck,

    * * *

    Temecula CA.USA
  6. First, you actually may get more out of the project by tuning shortwave
    frequencies. IN the broadcast band, you the regen won't actually mean
    that much on local stations, you may also find that the ease with
    which a regen can kick into oscillation will be annoying on the broadcast
    band that consists of AM signals, since the oscillation will beat against
    the carrier of the station and cause an annoying beat note.

    On shortwave, you get new territory, and the gain of the regen will start
    being useful. Plus, you'll come into contact with signals that require
    the regen to go into oscillation, so you get to sample that.

    On another matter, the thing about regen receivers is that they've often
    focused on simplicity. In the beginning, that reflected the cost of
    components, but then in more recent decades it's because there are better
    reception schemes, which are complicated, so the only reason to use
    regenerative receivers was for the simplicity.

    Yet, modern components have made it so easy to make things better. In
    the days of tubes, nobody wanted to add extra tubes since the cost was
    there and it increased the size of the receiver. But semiconductors are
    outright cheap, and their size means you can have hundreds or more
    transistors in the space that one tube took up.

    Charles Kitchin has done quite a bit of work on regen and superregen
    receivers, going back to the beginning (instead of cascading on what's
    been there recently), trying to distill the basic concept and seeing
    how to improve upon it. He's published quite a few different regen
    receivers (and some superregens) that are still relatively simple
    yet don't go for the fewest of components.

    So he'd add a stage of amplification before the regen detector, not
    because amplification was needed, but because it isolated the detector
    from the antenna, so the antenna moving around had less affect on
    the regen's operation (in the old days, a single stage regen would
    pop into oscillation because the antenna waved in the wind). It
    complicates the electronics, though only relatively speaking, but
    it simplifies useage. He'd add voltage regulation, again to help
    stabilize the amount of regeneration so it didn't suddenly pop
    into oscillation. In the tube days, voltage regulation would require
    another big tube, in solid state times, it's a diode or three terminal
    regulator, nice and easy.

    But most of his designs have also focused on being easy to build. So
    he uses things like 35mm plastic film boxes to wind the coils, though I
    suppose at this point those are getting scarce as film cameras disappear.
    In at least one design, he used a varactor for tuning, to sidestep
    the issue of getting a variable capacitor. He even had one that
    used a crystal for frequency selection, useless for most purposes
    but great when there was a code practice station on that frequency.

    So you might do a search on "charles kitchin", at least some of his
    designs have appeared on the web.

  7. Allen

    Allen Guest

    Before somebody swears at you, have you considered browsing to your
    search engine and entering 'LM386 datasheet'? It's free, it shows
    and you'll get a result FAR more quickly than waiting for somebody to do it
    for you.
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