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10645Shielded Resonant HF Loop

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  • jfarley44@...
    Jun 23, 2014
      A while back some insulators on a nearby power pole went crusty, and began to spew horrendous RFI around the neighborhood.  I prefer to DX with an unshielded resonant loop, and even with azimuthal "nulling" my noise floor here was way too high - about an S7 - for my liking.  After several calls to the Power Company over several weeks, I went into Repair Despair.  The backup AL1530 worked OK, but I knew that I was missing DX.

      I decided to see if I could get the best of both worlds, that is, a shielded resonant loop.  I built a prototype of the loop using one of my standard loops on a PVC frame, some foamboard, aluminum foil, and tons of Scotch tape.  Here's a pic:

      http://i1049.photobucket.com/albums/s387/jFarley44/LunarLander_zps4593ae91.jpg

      The idea was to enclose the resonant loop inside a cobbled up shield (maintaining a 3 to 4 inch gap between the windings and the shield) to see if that would help to suppress noise pickup.  The idea apparently has some merit, and here is a sample of audio capture which directly compares the audio capped with the unshielded standard RL to that capped with the shielded RL

      http://www.mediafire.com/listen/4rdk48824h6tnqd/CFRX_6070AM19Oct12_2030z.mp3

      The first 42 seconds of the audio is from the unshielded RL, and the balance is via the shielded RL.

      Shortly after the prototype was evaluated, the Power Company fixed the pole and I put this project on the back burner.  The shield gaps shown in the image are a first guess, and the lack of 100% coverage in the shield is just impatience showing through.  I just toss this out there as an idea to other loop builders who may wish to explore this area.

      I apologize for using direct links here; I am organizing my archives in the hope of creating more permanent refs in the Links section in the future.
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