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Re: Multi turn Mag. loop

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  • Michael Hebert
    Garth, For a _tuned_ loop increasing the number of turns moves the tuning range lower in frequency. For any given frequency, the single-turn tuned loop will
    Message 1 of 2 , Aug 20 11:42 AM
      Garth,

      For a _tuned_ loop increasing the number of turns moves the tuning
      range lower in frequency. For any given frequency, the single-turn
      tuned loop will have a larger diameter (and thus greater capture
      area) than a multi-turn tuned loop. This translates to greater
      sensitivity with a single-turn tuned loop. The sensitivity of the
      loop is directly related to its "Q" or effective bandwidth. The
      higher the Q, the narrower the bandwidth, the greater the sensitivity
      and the lower the noise.

      Thumb's Rule states that for best Q the multi-turn loop should have
      its turns spaced at least 1 conductor diameter.

      Depth of nulls will be affected by proximity to other objects in the
      near field of the loop on the horizontal plane. As the angle of
      signal arrival increases above the horizontal plane the depth of null
      will decrease. For signal arrival angles above 30 degrees the loop is
      essentially omnidirectional.

      The 1.0" hardline should make a very good loop. The only problem with
      it may be in the connections to the tuning capacitor. You will need
      to make them as mechanically and electrically sound as possible...
      and thoroughly weatherproofed to retard oxidation at the joints.

      73,

      'Bear' NH7SR

      --- In loopantennas@yahoogroups.com, "Garth M.Conover" <ewrtsa@m...>
      wrote:
      > I am looking for info as to a 3 or 5 turm Magnetic loop.(using 1.0"
      > hardline for outdoor stabilty) along with the usual tuning cap.
      Will
      > it produce any better results when campared to the same diameter
      mag
      > loop but just 1 turn. Will I get deeper nulls/improved directivity?
      > This is meant to be a rcv. loop only. I want to use large dia.
      > hardline due to its built in solid outer metal conductor. I figure
      It
      > will be easier to stabilize the turns. Which brings me to another
      > question. I realize turn counts Vs spacing is a consideration with
      > wire loops. But what are the implications with a multi turn coax
      > loop. Should the hardline turns be basiclly intimate with the black
      > plastic outer conductor touching or should the turns be seperated
      > by "X" I would think that there should be some sort of spacing. Any
      > guidance for those who have this info or links to find same would
      be
      > greatly appreciated.
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