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Shielded multi turn loop

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  • dxnature
    Hi all, I like to construct a multi turn shielded loop with RG6 coax. I have already a cross section frame with sides of 1.5 meters or 6 meters per turn. I
    Message 1 of 5 , Feb 1, 2008
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      Hi all,

      I like to construct a multi turn shielded loop with RG6 coax. I have
      already a cross section frame with sides of 1.5 meters or 6 meters per
      turn. I have a coil of 100 meter RG6 standing aside to use.

      My frequency range will be from 150 to 500 khz. Can I make a direct
      coupling with the transmission line or do I have to make a single turn
      coupler link. I like to use varicaps to remotely tune the loop.

      How can I proceede?

      Greetings,
      Ron
      ON3RON, DXA64
    • dxnature
      ... No ideas? Ron
      Message 2 of 5 , Feb 8, 2008
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        --- In loopantennas@yahoogroups.com, "dxnature" <amazingalgo@...> wrote:
        >
        > Hi all,
        >
        > I like to construct a multi turn shielded loop with RG6 coax. I have
        > already a cross section frame with sides of 1.5 meters or 6 meters per
        > turn. I have a coil of 100 meter RG6 standing aside to use.
        >
        > My frequency range will be from 150 to 500 khz. Can I make a direct
        > coupling with the transmission line or do I have to make a single turn
        > coupler link. I like to use varicaps to remotely tune the loop.
        >
        > How can I proceede?
        >
        > Greetings,
        > Ron
        > ON3RON, DXA64
        >

        No ideas?

        Ron
      • Steve
        Unless someone has already worked out a formula, it may be a bit of cut and try. There is at least one Javascript on a website in the Links section (also
        Message 3 of 5 , Feb 8, 2008
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          Unless someone has already worked out a formula, it may be a bit of
          cut and try. There is at least one Javascript on a website in the
          Links section (also mentioned recently, search for loop calculator in
          the archives) that calculates with a fixed spacing. You'll also have
          to take into account capacitance of the cable, there's where the
          cut-and-try comes in.

          I went and looked it up, here's Bruce Carter's javascript loop
          calculator. Uses turn spacing rather than loop width. Enter values,
          guessing at minimum capacitance, then calculate cable capacitance and
          use that to get a more accurate guess at minimum capacitance, repeat
          'til the values don't change.
          http://www.mindspring.com/~loop_antenna/umr_emc_calc.htm

          I would think a single loop coupling would be better than a direct
          connection. Less affect on loop capacitance, less loading of the tuned
          loop.

          Steve Greenfield

          --- In loopantennas@yahoogroups.com, "dxnature" <amazingalgo@...> wrote:
          >
          > Hi all,
          >
          > I like to construct a multi turn shielded loop with RG6 coax. I have
          > already a cross section frame with sides of 1.5 meters or 6 meters per
          > turn. I have a coil of 100 meter RG6 standing aside to use.
          >
          > My frequency range will be from 150 to 500 khz. Can I make a direct
          > coupling with the transmission line or do I have to make a single turn
          > coupler link. I like to use varicaps to remotely tune the loop.
          >
          > How can I proceede?
          >
          > Greetings,
          > Ron
          > ON3RON, DXA64
          >
        • John Stumm
          ... have ... meters per ... direct ... turn ... Ron, What you are envisioning sounds challenging and could present some problems to fuction effectively in a
          Message 4 of 5 , Feb 8, 2008
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            --- In loopantennas@yahoogroups.com, "dxnature" <amazingalgo@...>
            wrote:
            >
            > --- In loopantennas@yahoogroups.com, "dxnature" <amazingalgo@>
            wrote:
            > >
            > > Hi all,
            > >
            > > I like to construct a multi turn shielded loop with RG6 coax. I
            have
            > > already a cross section frame with sides of 1.5 meters or 6
            meters per
            > > turn. I have a coil of 100 meter RG6 standing aside to use.
            > >
            > > My frequency range will be from 150 to 500 khz. Can I make a
            direct
            > > coupling with the transmission line or do I have to make a single
            turn
            > > coupler link. I like to use varicaps to remotely tune the loop.
            > >
            > > How can I proceede?
            > >
            > > Greetings,
            > > Ron
            > > ON3RON, DXA64
            > >
            >
            > No ideas?
            >
            > Ron
            >
            Ron,
            What you are envisioning sounds challenging and could present some
            problems to fuction effectively in a remote application. I have
            entertained the thought of using remotely tuned amp such as the
            Ramsey signal magnet with a large remote air core. Unless you are in
            a truely remote location, it would be more of a noise magnet though.
            Shielding the loop using coax would involve breaking the shielding at
            the top of each turn. The coax that feeds the loop also supplies the
            tuning voltage. The loop can be 100's of ft away. Without knowing
            your skill level, employing this or something similar (like the Degen
            DE31?) could be easier to realize. If anything, maybe this will
            stimulate more discussion...

            Regards,
            John
          • dxnature
            Hi Steve, I made a conventional loop with 15 turns of wire on a 1.5 by 1.5 meter frame and 1 link coupling. It came almost on the resonated frequency I had
            Message 5 of 5 , Feb 18, 2008
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              Hi Steve,

              I made a conventional loop with 15 turns of wire on a 1.5 by 1.5
              meter frame and 1 link coupling. It came almost on the resonated
              frequency I had calculated. It tuned from 700 to 200 khz. Sorry to say
              there is bit less noise and the signals are a bit stronger but not as
              I expected it to be. Ok it is a step in the right direction but I'm
              not content. There is still to mutch noise!!!

              What I want to do right now is to replace the link coupling with a
              coax loop as pick-up and connect this to the feed line. What do you
              think? Will this give me a bit less noise?

              Greetings,
              Ron
              >
              > Unless someone has already worked out a formula, it may be a bit of
              > cut and try. There is at least one Javascript on a website in the
              > Links section (also mentioned recently, search for loop calculator in
              > the archives) that calculates with a fixed spacing. You'll also have
              > to take into account capacitance of the cable, there's where the
              > cut-and-try comes in.
              >
              > I went and looked it up, here's Bruce Carter's javascript loop
              > calculator. Uses turn spacing rather than loop width. Enter values,
              > guessing at minimum capacitance, then calculate cable capacitance and
              > use that to get a more accurate guess at minimum capacitance, repeat
              > 'til the values don't change.
              > http://www.mindspring.com/~loop_antenna/umr_emc_calc.htm
              >
              > I would think a single loop coupling would be better than a direct
              > connection. Less affect on loop capacitance, less loading of the tuned
              > loop.
              >
              > Steve Greenfield
              >
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