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Re: [loopantennas] concentric loops

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  • richard
    On Sun, 7 Mar 2010 09:14:13 -0800 (PST) ... yes that kinda thing Kevin , I was thinking of something covering 18-24 MHz. Maybe orthogonal as Chris suggested.
    Message 1 of 11 , Mar 7, 2010
      On Sun, 7 Mar 2010 09:14:13 -0800 (PST)
      kevin asato <kc6pob@...> wrote:

      > I don't know how well it works, but like this for example? -
      > http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=481
      >
      > 73,
      > kevin
      > kc6pob
      >
      yes that kinda thing Kevin , I was thinking of something covering 18-24 MHz.
      Maybe orthogonal as Chris suggested.
      With that design, I'm guessing that there maybe a fair bit of interaction between them, hence the
      need for preamps.

      Maybe give it a try, I thought maybe worth asking as there's no point in try to invent the wheel.

      Thanks
      --
      Best wishes

      Richard Bown

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      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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    • 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 2 of 11 , Mar 7, 2010
        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 3 of 11 , Mar 7, 2010
          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 4 of 11 , Mar 7, 2010
            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 5 of 11 , Mar 7, 2010
              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 6 of 11 , Mar 7, 2010
                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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