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7372RE: [loopantennas] Loop Capacitance

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  • Chris Harris
    Apr 1 4:50 AM
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      All my loops have fed from the top and tune at the tune at the bottom as
      the cap is heavy and the feed is not. The feed loop is untuned and the
      line runs down the centre line of the support pole, keeping everything
      symmetrical as reasonably possible although I wonder how much the feed
      loop being unbalanced upsets the symmetry due to capacitive interaction.

      Any thoughts on this anyone?

      I think you will want to tune the capacitance of your 11m loop as it
      will be tuning over ~1.2% and you can expect a Q in the 100s if the
      thing is well built and if it isn't it won't work.....

      For you're frequency, a simple DIY variable capacitor should be pretty
      easy to conjure up as you only need 20pF or so. I have seen cute designs
      using water pipe or copper sheet or PCB laminate.

      C



      -----Original Message-----
      From: loopantennas@yahoogroups.com [mailto:loopantennas@yahoogroups.com]
      On Behalf Of ozzy_1kw
      Sent: Thursday, 1 April 2010 7:12 p.m.
      To: loopantennas@yahoogroups.com
      Subject: [loopantennas] Loop Capacitance






      If the tuning is done by the small loop for best swr then for a single
      band hf cb i can put the exact capacitance required or is the tuning too
      sharp to cover the entire cb band??

      what is the purpose for the variable capacitor ,is it multiband usage ?

      TY Rob

      PS, i see on youtube the guy that sells loops.his appear to be upside
      down with the tuning capacitor on the bottom that he tunes with his
      thumb. is there any issues feeding it from the top and running the coax
      down the side of the loop ?

      Cheers Rob







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