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Re: [loopantennas] concentric loops

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  • richard
    On Sun, 07 Mar 2010 12:18:31 -0500 ... Thanks Jim. I ll start collecting parts to build one. -- Best wishes Richard Bown
    Message 1 of 11 , Mar 7, 2010
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      On Sun, 07 Mar 2010 12:18:31 -0500
      Jim Dunstan <jimdunstan@...> wrote:

      > At 04:00 PM 3/7/2010 +0000, you wrote:
      > >
      > >
      > >Hi
      > >might sound a daft idea, but
      > >can you place one loop inside another so its on the same axis ,
      > >but resonant at a higher frequency ?
      > >TIA
      > >--
      > >Best wishes
      > >
      > >Richard Bown
      >
      > Hi Richard,
      >
      > You certainly can. That is in fact how one constructs a multi-band Quad
      > antenna.
      >
      > Jim, VE3CI
      >
      >
      Thanks Jim. I'll start collecting parts to build one.

      --
      Best wishes

      Richard Bown

      ###################################################################################
      Registered Linux User 36561
      OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
      Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz & 5.7GHz & 10 GHz
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    • Jim Dunstan
      ... Hi Richard, As an addendum: concentric full self resonant loops are of a manageable size in the VHF range ... as you move into HF they are commonly used
      Message 2 of 11 , Mar 7, 2010
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        At 12:18 PM 3/7/2010 -0500, you wrote:
        >
        >
        >At 04:00 PM 3/7/2010 +0000, you wrote:
        > >
        > >
        > >Hi
        > >might sound a daft idea, but
        > >can you place one loop inside another so its on the same axis ,
        > >but resonant at a higher frequency ?
        > >TIA
        > >--
        > >Best wishes
        > >
        > >Richard Bown
        >
        >Hi Richard,
        >
        >You certainly can. That is in fact how one constructs a multi-band Quad
        >antenna.
        >
        >Jim, VE3CI

        Hi Richard,

        As an addendum: concentric full self resonant loops are of a manageable
        size in the VHF range ... as you move into HF they are commonly used from
        14 mhz to 28 mhz .... and rotatable. At frequencies below 14 mhz they are
        very large and almost always single fixed loops.

        Small loops .... less than 1/10 wavelength are by definition non resonant
        (unless they are tuned) and putting 2 loops on the same axis makes little
        sense .... the exception being loops used for direction finding ... in
        which case they are mounted at right angles to each other. the reason for
        using 2 loops is that the null can be rotated electronically in the radio
        room instead of actually mechanically rotating the loops.

        Jim, VE3CI
      • richard
        On Sun, 07 Mar 2010 13:51:56 -0500 ... Hi Jim the reason for thinking of the concentric mag loops , is The mage loop I ve just built 4mtrs in diameter tunes
        Message 3 of 11 , Mar 7, 2010
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          On Sun, 07 Mar 2010 13:51:56 -0500
          Jim Dunstan <jimdunstan@...> wrote:

          > At 12:18 PM 3/7/2010 -0500, you wrote:
          > >
          > >
          > >At 04:00 PM 3/7/2010 +0000, you wrote:
          > > >
          > > >
          > > >Hi
          > > >might sound a daft idea, but
          > > >can you place one loop inside another so its on the same axis ,
          > > >but resonant at a higher frequency ?
          > > >TIA
          > > >--
          > > >Best wishes
          > > >
          > > >Richard Bown
          > >
          > >Hi Richard,
          > >
          > >You certainly can. That is in fact how one constructs a multi-band Quad
          > >antenna.
          > >
          > >Jim, VE3CI
          >
          > Hi Richard,
          >
          > As an addendum: concentric full self resonant loops are of a manageable
          > size in the VHF range ... as you move into HF they are commonly used from
          > 14 mhz to 28 mhz .... and rotatable. At frequencies below 14 mhz they are
          > very large and almost always single fixed loops.
          >
          > Small loops .... less than 1/10 wavelength are by definition non resonant
          > (unless they are tuned) and putting 2 loops on the same axis makes little
          > sense .... the exception being loops used for direction finding ... in
          > which case they are mounted at right angles to each other. the reason for
          > using 2 loops is that the null can be rotated electronically in the radio
          > room instead of actually mechanically rotating the loops.
          >
          > Jim, VE3CI
          >
          >
          >
          >

          Hi Jim the reason for thinking of the concentric mag loops , is The mage loop I've just built
          4mtrs in diameter tunes from 40 mtrs thru to 80 and with an additional cap switched in will cover
          most of top band.
          I'm OK for antennas for 14,21.28,50,70,144,432,1296,2320,5760 and 10368 MHz.

          I have a hole for 18 & 24 MHz, I can resonate the feeder on the 7/14 MHz dipole but its a pig
          and takes a lot of fiddling with the ATU to get it right.
          A 1.2 mtr mag loop tuned with 5 -20pF would fill the hole, and thats why the questiopn of putting
          them concentrically.

          HTH

          --
          Best wishes

          Richard Bown

          ###################################################################################
          Registered Linux User 36561
          OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
          Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz & 5.7GHz & 10 GHz
          ###################################################################################
        • Jim Dunstan
          ... Hi Richard, Putting tuned magnetic loops on the same axis is a different story. I assume that doing so is for reasons of access or convenience. Unlike
          Message 4 of 11 , Mar 7, 2010
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            At 09:42 PM 3/7/2010 +0000, you wrote:
            >
            >
            >On Sun, 07 Mar 2010 13:51:56 -0500


            >Hi Jim the reason for thinking of the concentric mag loops , is The mage
            >loop I've just built
            >4mtrs in diameter tunes from 40 mtrs thru to 80 and with an additional cap
            >switched in will cover
            >most of top band.
            >I'm OK for antennas for 14,21.28,50,70,144,432,1296,2320,5760 and 10368 MHz.
            >
            >I have a hole for 18 & 24 MHz, I can resonate the feeder on the 7/14 MHz
            >dipole but its a pig
            >and takes a lot of fiddling with the ATU to get it right.
            >A 1.2 mtr mag loop tuned with 5 -20pF would fill the hole, and thats why
            >the questiopn of putting
            >them concentrically.
            >
            >HTH
            >
            >--
            >Best wishes
            >
            >Richard Bown

            Hi Richard,

            Putting tuned magnetic loops on the same axis is a different story. I
            assume that doing so is for reasons of access or convenience. Unlike full
            size loops the tuning one mag loop will have considerably more affect on
            the resonance of the other loop. In that case it would probably be
            advisable to orient them in a position that has the least inductive
            interaction ... probably at right angles to each other ... as I think
            someone else has suggested.

            Jim,

            VE3CI
          • richard
            On Sun, 07 Mar 2010 17:13:14 -0500 ... Hi Jim I had a hunch that it would not be a s simple as hang one one inside the other, :) Getting the 80 mtr mag loop
            Message 5 of 11 , Mar 7, 2010
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              On Sun, 07 Mar 2010 17:13:14 -0500
              Jim Dunstan <jimdunstan@...> wrote:

              > At 09:42 PM 3/7/2010 +0000, you wrote:
              > >
              > >
              > >On Sun, 07 Mar 2010 13:51:56 -0500
              >
              >
              > >Hi Jim the reason for thinking of the concentric mag loops , is The mage
              > >loop I've just built
              > >4mtrs in diameter tunes from 40 mtrs thru to 80 and with an additional cap
              > >switched in will cover
              > >most of top band.
              > >I'm OK for antennas for 14,21.28,50,70,144,432,1296,2320,5760 and 10368 MHz.
              > >
              > >I have a hole for 18 & 24 MHz, I can resonate the feeder on the 7/14 MHz
              > >dipole but its a pig
              > >and takes a lot of fiddling with the ATU to get it right.
              > >A 1.2 mtr mag loop tuned with 5 -20pF would fill the hole, and thats why
              > >the questiopn of putting
              > >them concentrically.
              > >
              > >HTH
              > >
              > >--
              > >Best wishes
              > >
              > >Richard Bown
              >
              > Hi Richard,
              >
              > Putting tuned magnetic loops on the same axis is a different story. I
              > assume that doing so is for reasons of access or convenience. Unlike full
              > size loops the tuning one mag loop will have considerably more affect on
              > the resonance of the other loop. In that case it would probably be
              > advisable to orient them in a position that has the least inductive
              > interaction ... probably at right angles to each other ... as I think
              > someone else has suggested.
              >
              > Jim,
              >
              > VE3CI
              >
              >
              >
              Hi Jim
              I had a hunch that it would not be a s simple as hang one one inside the other, :)
              Getting the 80 mtr mag loop within 15@ of the tower the VHF arrays are on detuned it, surprisingly
              it resonated higher in frequency, I would have expected lower.
              I'll gather the bits I need and play..

              thanks

              --
              Best wishes

              Richard Bown

              ###################################################################################
              Registered Linux User 36561
              OS: Mandriva 2010.0 Powerpack on an AMD Dual Athlon 64 +4400: 8 GB RAM DDR2
              Ham Call: G8JVM , QRA IO82SP, Interests Microwave 1.3 GHz,2.3 GHz & 5.7GHz & 10 GHz
              ###################################################################################
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