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Question About AM Loops

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  • march181959
    I m trying to understand this loop thing conceptually. Given the two different configurations, why does a small loop or coil with a ferrite rod work well
    Message 1 of 2 , Sep 29, 2006
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      I'm trying to understand this loop thing conceptually. Given the two
      different configurations, why does a small loop or coil with a ferrite
      rod work well inside a radio, whereas a long Beverage type antenna
      also work just as well? Is it the length of the total wire? Does the
      3 dimensional configuration of the loop/coil catch the wave better,
      especially since reception is directional? If you build a coil, like
      a hula hoop type antenna with a few turns, no ferrite rod is
      required. I'm thinking the magenetic component of the radio wave
      induces a modulated voltage in the wire, but not sure what the key is
      here. The better I understand it, the more ideas I'll have to try.

      Thanks...

      Frank
    • Bruce Carter
      ... Loops are magnetic field antennas instead of electrostatic field antennas. The larger the area of the loop, the more lines of magnetic flux it intercepts.
      Message 2 of 2 , Oct 2, 2006
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        > I'm trying to understand this loop thing conceptually. Given the

        Loops are magnetic field antennas instead of electrostatic field
        antennas. The larger the area of the loop, the more lines of magnetic
        flux it intercepts. That is why a ferrite bar antenna works - the
        ferrite concentrates magnetic flux in what would ordinarily be a loop
        that is too small to be effective.

        Having never built a beverage antenna for these frequencies due to lack
        of space, I can't really speak to why it works. However, I suspect it
        is because - even with low gain - it is large enough to intercept the
        magnetic flux. It is therefore a great broadband solution, if you have
        the land to construct it.

        The smaller tuned loops we discuss here take advantage of parallel
        resonant bandpass filter characterisitics to have gain.
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