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Re: Define loop antenna

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  • Anders
    ... Hello Bill! Check this site: http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=3274 /Anders
    Message 1 of 6 , Aug 19, 2006
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      --- In loopantennas@yahoogroups.com, "Bill Boyd" <wboyd530@...> wrote:
      >
      > Hi All
      > I'm new to the group and have a question. If I run a wire around the
      > outside of my house totalling about 130 to 140 feet is that a loop
      > antenna. Or does it have to be vertical? I have a small lot and not
      > much room for long wire. I am trying to figure our the best low noise
      > antenna in a high electrical noise heighborhood environment. My back
      > yard has three different house feeds running across it and my front
      > yard is about 20 feet deep, so the roof is about the only place to run
      > an antenna. Any help is greatly appreciated.
      > Thanks
      > Bill Boyd
      >

      Hello Bill!
      Check this site:
      http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=3274

      /Anders
    • Jim Dunstan
      ... Hi Bill, A loop is a loop no matter what its orientation .... eg vertical, horizontal, or something in between. Since we are talking definition .... there
      Message 2 of 6 , Aug 19, 2006
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        At 05:56 PM 19/08/2006 +0000, you wrote:

        >Hi All
        >I'm new to the group and have a question. If I run a wire around the
        >outside of my house totalling about 130 to 140 feet is that a loop
        >antenna. Or does it have to be vertical? I have a small lot and not
        >much room for long wire. I am trying to figure our the best low noise
        >antenna in a high electrical noise heighborhood environment. My back
        >yard has three different house feeds running across it and my front
        >yard is about 20 feet deep, so the roof is about the only place to run
        >an antenna. Any help is greatly appreciated.
        >Thanks
        >Bill Boyd

        Hi Bill,

        A loop is a loop no matter what its orientation .... eg vertical,
        horizontal, or something in between. Since we are talking definition ....
        there are few basic categories into which all antennas fit. First there is
        what is called a dipole antenna .... eg it is a wire in space with 2
        separate ends along which antenna currents flow. This wire in space can be
        coupled to your radio/transmitter by a feed line that is located in the
        center (center fed dipole) or at the end (end fed dipole), or somewhere in
        between.

        Now, if you take that dipole and join the ends together to form a loop then
        you will have a loop antenna. Both antennas are what are called 'balanced'
        antennas .... that is the RF currents are running within the antenna and
        not between the antenna and ground (or at least you hope that is the
        case). These two types of antennas which are balanced are in contrast to
        the last category which you can call a 'monopole' antennas.

        Monopole antennas are not 'balanced' .... one end of the antenna is
        connected to ground (earth) and the other end is (usually) perpendicular to
        the earth. The antenna currents flow from one end of the wire to earth
        and back and therefore are not 'balanced'. Most of these kinds of antennas
        are called 'verticals' eg the most efficient direction to run the antenna !!

        All antennas are designs based on the 3 possible configurations, the
        dipole, the loop, or the vertical (and sometimes one is mistaken for the
        other).

        Now designing the antenna for minimum received RFI (noise) is another
        matter not necessarily related to choosing between loop, dipole, or vertical.

        Jim
      • davis gates
        ... run ... Bill That is a loop antenna. Yours would be called a long wire loop since it is a significant fraction of a wavelength long. These are highly
        Message 3 of 6 , Aug 20, 2006
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          --- In loopantennas@yahoogroups.com, "Bill Boyd" <wboyd530@...> wrote:
          >
          > Hi All
          > I'm new to the group and have a question. If I run a wire around the
          > outside of my house totalling about 130 to 140 feet is that a loop
          > antenna. Or does it have to be vertical? I have a small lot and not
          > much room for long wire. I am trying to figure our the best low noise
          > antenna in a high electrical noise heighborhood environment. My back
          > yard has three different house feeds running across it and my front
          > yard is about 20 feet deep, so the roof is about the only place to
          run
          > an antenna. Any help is greatly appreciated.
          > Thanks
          > Bill Boyd
          >

          Bill
          That is a loop antenna. Yours would be called a "long wire loop" since
          it is a significant fraction of a wavelength long.
          These are highly efficient antennas. I use one for transmitting and
          receiving low band DX. It has a low angle of radiation (and reception)
          on the second harmonic. The primary frequency has too much near
          vertical radiation and reception to be of much use except for local
          communications.
          You will need a tuner.
          A good discussion of these antennas is in the magazine "World Radio" in
          several issues, summer 2005.
          Hope this helps.
          Dave Ag4K
        • dldorrance
          ... definition .... ... there is ... can be ... somewhere in ... loop then ... balanced ... and ... contrast to ... perpendicular to ... earth ... antennas
          Message 4 of 6 , Aug 20, 2006
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            --- In loopantennas@yahoogroups.com, Jim Dunstan <jdunstan@...> wrote:
            >
            > At 05:56 PM 19/08/2006 +0000, you wrote:
            >

            >
            > Hi Bill,
            >
            > A loop is a loop no matter what its orientation .... eg vertical,
            > horizontal, or something in between. Since we are talking
            definition ....
            > there are few basic categories into which all antennas fit. First
            there is
            > what is called a dipole antenna .... eg it is a wire in space with 2
            > separate ends along which antenna currents flow. This wire in space
            can be
            > coupled to your radio/transmitter by a feed line that is located in the
            > center (center fed dipole) or at the end (end fed dipole), or
            somewhere in
            > between.
            >
            > Now, if you take that dipole and join the ends together to form a
            loop then
            > you will have a loop antenna. Both antennas are what are called
            'balanced'
            > antennas .... that is the RF currents are running within the antenna
            and
            > not between the antenna and ground (or at least you hope that is the
            > case). These two types of antennas which are balanced are in
            contrast to
            > the last category which you can call a 'monopole' antennas.
            >
            > Monopole antennas are not 'balanced' .... one end of the antenna is
            > connected to ground (earth) and the other end is (usually)
            perpendicular to
            > the earth. The antenna currents flow from one end of the wire to
            earth
            > and back and therefore are not 'balanced'. Most of these kinds of
            antennas
            > are called 'verticals' eg the most efficient direction to run the
            antenna !!
            >
            > All antennas are designs based on the 3 possible configurations, the
            > dipole, the loop, or the vertical (and sometimes one is mistaken for
            the
            > other).
            >
            > Now designing the antenna for minimum received RFI (noise) is another
            > matter not necessarily related to choosing between loop, dipole, or
            vertical.
            >
            > Jim
            >

            Bill, to add to Jim's explanation it is useful to expand on the
            polarization vs near field noise issue, as you outlined noise as a
            reason to use a loop antenna on your small lot. As an aside, I
            sympathize with your problem, as my small lot has power line easements
            on 2 sides making it very noisy.

            The loop you describe, although parallel to the ground, is vertically
            polarized as loop polarization is opposite dipole polarization. Man
            made noise is principally vertically polarized. This means your loop
            will not decrease locally generated noise.

            As a start, you might do better by stringing a dipole around the
            house, whether resonant or not, as the dipole would tend to reject
            noise better than a loop similarly situated.

            There is a caveat here. If either type of antenna above is under 1/2
            wavelength from the earth, the angle of radiation will be high,
            diminishing ability to receive and/or transmit to distant stations.

            A better solution would be a horizontally polarized loop, that is, one
            whose plane is perpendicular to the earth. That way the polarization
            diminishes the noise and as a bonus you may rotate the loop to null
            the noise. Furthermore, this type of loop works well under 1/2
            wavelength above the earth.

            Because of size constraints of your property, a small, horizontally
            polarized loop might be ideal, though more complicated to construct.
            The construction depends upon the purpose of the loop, as receive-only
            small loops have different requirements than transmit-receive small loops.

            Dave WA6YSO
          • Bill Boyd
            Thanks to all that answered my request. I Think I will like being a part of this group. I probably should have been a little clearer in my request. I was
            Message 5 of 6 , Aug 20, 2006
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              Thanks to all that answered my request. I Think I will like being a part of this group. I probably should have been a little clearer in my request. I was mainly worried about not picking up electrical noise. I've been around short wave off and on for 40 years. never did study it much, just enjoyed listening. Now I,m co-owner of scanner talk on Yahoo and we are getting into HF military monitoring. My old DX-440 didn't quite cut the mustard here in the midwest so i picked up a IC-R75 Icom and love it. Ijust need a good antenna on a small lot. Not much to ask. Right? Ya, I know. People in heck want ice water to. Oh ya, did I mention cheap. I definatly need cheap. Well as usual i've rambled on to much again. But again thanks.
              Bill B


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