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How to make metal building opaque to FM transmitter inside building?

Discussion in 'Electronic Basics' started by Eric R Snow, Feb 10, 2004.

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  1. Eric R Snow

    Eric R Snow Guest

    To the radio Folks,
    Thanks for the tips on using an antenna to get FM signals into my
    metal building. Now, I'm contemplating sort of the opposite. Ramsey
    and others sell FM transmitters. These can be connected to the sound
    card in a computer. Letting a person listen to web broadcasts. One
    transmitter is weak enough that FCC rules allow anyone to use one. My
    brother built one and I've used it. It drifts with temperature. And my
    portable radio is digitally tuned. Also, it just doesn't sound that
    good. They sell another transmitter that is supposed to stay on the
    set frequency. But I think the power it puts out may violate FCC rules
    for me. My steel building is built on a two foot high concrete stem
    wall. I am thinking that's how I get any kind of radio reception at
    all inside. Before the insulation is put up if the stem wall was
    covered with chicken wire would that stop my puny transmitter from
    getting out and bothering the neighbors? I know, this almost sounds
    like a tin foil beanie question but I'm serious.
    Thank You,
    Eric R Snow,
    E T Precision Machine
  2. Metal buildings leak RF at all seams, so your building may radiate FM
    quite well. I think you can distribute low power FM throughout the
    building without much far field production by connecting the
    transmitter to a leaky piece of coax that is routed all around the
    inside of the building. You make a coax leaky by making small
    openings in the shield every foot or so. I think you want to to vary
    the distance between holes so it doesn't have a periodic frequency
    response. You may need to terminate the end of the line in a resistor
    but if the line is lossy enough this may not make much of a
    difference. Be sure to go outside with a portable radio and check for
    whether the transmission is getting much past the property line.
  3. andrew22


    Feb 2, 2011
    thx for all of my questions, but what about the traditional radio, you have written about the online computer radio which broadcast through internet, will your transmitter also work with traditional radio.
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