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Discussion in 'Misc Electronics' started by Roger Dewhurst, Aug 14, 2009.

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  1. I recall reading that if an AM radio is tuned to frequency x plus or
    minus the heterodyne frequency a radio tuned to frequency x will be
    blotted out. Is this true? If so what is the heterodyne frequency?
    Will it work with FM?
  2. Don Bruder

    Don Bruder Guest

    If you're speaking purely about receiving rigs, POSSIBLY... (but
    probably only under very specific conditions) for a TX/RX rig, the
    situation changes drastically.
    I'm quite sure you'll find that varies from radio model to radio model.
    There's nothing "magic" about it - It's just the frequency the designers
    picked for the heterodyning process. In theory, it could be any
    frequency the designers care to choose. In practice, there are some
    limitations (imposed by both the laws of physics, and the available
    parts to build the beast) on what frequencies can be used with a given
    reception frequency range to get decent results.
    See first answer.
  3. I am talking about off the shelf transistorized receivers which usually,
    here at least permit reception of both AM medium wave and FM.
    I see no mention of FM in the first answer.

  4. Wim Lewis

    Wim Lewis Guest

    The idea is that the first radio's LO is leaking and will interfere with
    the signal? I guess I don't see why that wouldn't happen, if the first
    radio is poorly made and/or the signal is weak.
    I think it's usually 455 kHz for AM and 10.7 MHz for an FM receiver, but
    as another poster said, it's entirely up to the radio's designers.

    An FM receiver might be less susceptible to this kind of interference
    because of the FM "capture effect". Or maybe it would me more susceptible.
    I dunno.
  5. Don Bruder

    Don Bruder Guest

    Use a brain-cell, dude...

  6. No. A is driven mad by continual noise from the radio of B. A would
    like to deter B from keeping his radio switched on all day.

  7. My brain cells work OK when applied to matters I know something about.
    I doubt that your brain cells would be much use in dealing with matters
    that I know something about however well they may work in relation to
    matters you know something about. e.g. I imagine that all you know
    about proving up uranium ore reserves in sedimentary rocks could be writ
    large on the back of postage stamp.

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