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broadcast audio signal

Discussion in 'Electronic Basics' started by [email protected], Apr 19, 2007.

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  1. Guest

    I was just wondering if you can broadcast an audio signal (100 Hz to
    20 kHz) over the airwaves without upconverting it.

    Are there any problems with doing this?
  2. That's a huge bandwidth, about nine octaves. You can do it over short
    ranges with magnetic coupling, but if you want more than a few feet of
    range, upconverting to RF or modulated light is the only way to go.
  3. Phil Allison

    Phil Allison Guest

    ** Go look up "audio induction loop''.

    ....... Phil
  4. jasen

    jasen Guest

    Yes, It's done for hearing aids, it's called an inductive loop and has only
    a short range.

  5. Eeyore

    Eeyore Guest

    Induction loop. That'll cover a modest area.

  6. Bob Masta

    Bob Masta Guest

    If you actually want this to be an RF signal (in the
    Extremely Low Frequency range) you will need the
    mother of all antennas. IIRC, the US military (used to?)
    use this range for communications with submerged
    submarines. For a while they planned to use the
    entire Upper Penninsula of Michigan as the
    transmitting antenna, by virtue of its extensive iron
    and copper deposits. The system was intended
    for transmitting (at incredibly low bit rate) simple
    nuclear missile launch instructions. There was a big flap over it
    at the time (1980s maybe?), then we never heard
    any more about it. Hopefully it died with the cold war.
    But then again, one might have said that about the
    Star Wars projects as well, and they seem to still be
    with us....

    Best regards,

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
  7. default

    default Guest

  8. default

    default Guest

    They use induction loop systems for the hearing impaired in
    auditoriums - big loop in the floor is modulated with the audio signal
    and individual receivers pick up and amplify the signal. Better than
    a hearing aid, because you don't amplify the ambient noise just the
    program material.

    Some folks used to put them in their houses for music and there might
    be some info on the web how to go about it on a small scale.
  9. Tom Biasi

    Tom Biasi Guest

    How about a loudspeaker?
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