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small 160m rx loop and ferrite

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  • Sam Morgan
    I d like to ask about what ferrite mix to use at the feed of a small rx loop I have built this is NOT a shielded loop with the break in the shield half way
    Message 1 of 1 , Jul 3, 2012
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      I'd like to ask about what ferrite mix to use at the feed of a small rx loop I
      have built

      this is NOT a shielded loop
      with the break in the shield half way around the loop

      I made the loop out of the 2 turns of 5/8 inch hardline I had available
      the circumference is about 12'
      I am using only the shield as a continuous 2 turn loop

      for the feedline I just attached a 50 ohm coax with the
      coax center to one end of the hardline shield
      and the coax shield to the other end of the hardline shield

      it worked fine for what I wanted
      in the sense that it allowed me to null
      some thunderstorm crash noise during the Summer Stew
      allowing me to diversity receive with my outside vertical on my K3
      (it even works on 80m and 40m, so the toroid needs to work 160m-40m)

      however the pattern is not symmetrical
      (I think this is due to the unbalanced 15' of direct coax feedline?)

      so I think my next step would be to use a toroid as a balun
      with each end of the hardline loop attached by a couple of turns on the toroid
      and maybe twice that many turns on the other side of the toroid
      going to my 15 feet of 50 ohm coax to the rig


      I might later get around to building a preamp for it
      but for now all I want to do is add the toroid
      in the hopes that it will maybe make the pattern more symmetrical

      if I understand this correctly
      I am wanting to use a broadband coupling FTxx-xx ferrite core
      rather than a narrow high Q like I would get with powdered iron Txx-xx core

      I have an FT240-31, as well as FT37-61, and a FT50-61 on hand in my part bin.
      they were left overs from an order from Tony at
      http://partsandkits.com/toroids.php

      I used all the hard line I had on hand
      so different lengths, configurations etc etc etc
      is not my question, for now.......

      for now I just want to know what mix toroid I need to use
      between this loop and the coax feed to it
      I'm going at this as a step by step learning experiment


      I was planing on 4 turns on the primary and 16 turns on the secondary
      my reasoning being that might also give me a little signal increase as well?


      perhaps later I might get into the matching aspects of this experiment
      but I had plenty of signal strength using the coax directly
      with the loop setting in my 'other room' of my ground floor apartment
      I just thought it would be nice to have a symmetrical pattern
      rather than the odd ball one I have now

      --

      GB & 73
      K5OAI
      Sam Morgan
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