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15 Inch BCB Loop Antenna Idea

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  • Scott Savage KC7WDG
    Hi, I got given some poly square plastic stuff and thought hmm I could use this in a loop somehow and this popped into my mind I am thinking 15 inches on the
    Message 1 of 4 , Jul 27, 2004
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      Hi,

      I got given some poly square plastic stuff and thought hmm I could use this
      in a loop somehow and this popped into my mind I am thinking 15 inches on
      the outside with wood and the lengths on the inside holding it together that
      poly square plastic stuff is 1/2 inch square. So that would make the loop
      14.5in square not huge but decent I figure. I was thinking of bringing the
      coupling loop in about an inch or two from that so the coupling loop would
      be 13.5in or so to 12.5in not sure which is better. was going to make the
      "plate" to hold the cap out of lexan and the "plate" for the connections
      back to the receiver. question is how many turns of wire for the AM BCB I am
      sure there is a calc for this but I haven't seen it and I wanted to share my
      design. Also the rest wood be made from wood the longer pieces.


      Scott
      KC7WDG

      Image of Design Is Here >
      http://jupiter.walagata.com/w/bh420/15BCBLOOPIDEA.gif

      Any thoughts or suggestions are certainly welcome as this is an idea I
      haven't started building yet.
    • Jim Dunstan
      ... I have a BCB loop constructed on a plywood rectangle 10 1/2 x 14 . I placed a 2 peg at each corner. I wound 16 turns of Radio Shack hook up wire around
      Message 2 of 4 , Jul 27, 2004
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        At 11:33 AM 7/27/04 -0600, you wrote:
        >Hi,
        >
        >I got given some poly square plastic stuff and thought hmm I could use this
        >in a loop somehow and this popped into my mind I am thinking 15 inches on
        >the outside with wood and the lengths on the inside holding it together that
        >poly square plastic stuff is 1/2 inch square. So that would make the loop
        >14.5in square not huge but decent I figure. I was thinking of bringing the
        >coupling loop in about an inch or two from that so the coupling loop would
        >be 13.5in or so to 12.5in not sure which is better. was going to make the
        >"plate" to hold the cap out of lexan and the "plate" for the connections
        >back to the receiver. question is how many turns of wire for the AM BCB I am
        >sure there is a calc for this but I haven't seen it and I wanted to share my
        >design. Also the rest wood be made from wood the longer pieces.
        >
        >
        >Scott
        >KC7WDG

        I have a BCB loop constructed on a plywood rectangle 10 1/2" x 14". I
        placed a 2" peg at each corner. I wound 16 turns of Radio Shack hook up
        wire around the pegs.

        The plywood sheet is mounted vertically on a wood block which acts as a
        base. I mounted a 365pfd capacitor in the center of the sheet on the side
        opposite the windings. My Hi-Fi set came with a BCB antenna which
        consisted of a small plastic hoop about 8" in dia. with 3 turns of wire on
        it. I use this small loop as the pickup loop for my tuned loop. I
        attached this 8" hoop to the sheet the centre of my tuned loop. The 8"
        hoop has a twisted pair about 2' long terminated in spade lugs.

        Under normal BCB receiving conditions I have the tuned loop sitting on top
        of my HI Fi set with the twisted pair connected to the antenna input on the
        receiver. When I tune the loop to the received station the difference in
        reception increases a quantum leap.

        When I attempt DX reception with this tuned loop and a portable receiver
        out in the garden (minimize the local noise) I find that the placement of
        the pickup loop inside the tuned loop provides too much coupling. At first
        I dismounted the 8" loop and moved it farther and closer by hand to find
        the optimum coupling which is a balance between best selectivity/signal
        strength. I soon got tired and mounted one end of a 12" dowel to the
        plywood sheet and just hung the 8" pickup coil on this 'peg'. I could
        shuttle it from inside the loop to about 10" away from the loop. What I
        find is that under certain conditions ... eg separating close stations ....
        the pickup loop works best hanging on the peg up to 8" away from the tuned
        loop! I find that the placement of the pickup loop is almost as critical
        as the tuning of the main loop itself.

        One of the advantages of making the tuned loop relatively small is that it
        is portable. I would not be able to put a 4' loop on the table out in the
        garden hi. Another thing you might want to experiment with is using your
        tuned loop with a longwire antenna and ground. I have a longwire available
        out in the garden and I connected it to one side of the tuning
        capacitor. A ground wire was connected to the other side. The reception
        increases a second quantum leap. Again adjust the tuning and coupling for
        best reception ..... you will be amazed at the daytime reception with this
        setup. I say daytime because night time reception is completely different
        with all kinds of different stations coming in on skip. All my BCB DXing
        is daytime.

        So back to your questions:

        your loop will be about 13.5x12.5 ..... mine is 10.5x14 and it
        uses 16 turns.
        your pickup loop mounted inside the loop ...... mine is variable and some
        conditions works best at up 8" away from the loop!

        Jim Dunstan
        Thunder Bay, ON
      • Jim Dunstan
        ... My second post. I took a look at your construction schematic. U are using 4 pegs sandwiched between 2 frames. My construction is similar but different.
        Message 3 of 4 , Jul 27, 2004
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          At 11:33 AM 7/27/04 -0600, you wrote:
          >Hi,
          >
          >I got given some poly square plastic stuff and thought hmm I could use this
          >in a loop somehow and this popped into my mind I am thinking 15 inches on
          >the outside with wood and the lengths on the inside holding it together that
          >poly square plastic stuff is 1/2 inch square. So that would make the loop
          >14.5in square not huge but decent I figure. I was thinking of bringing the
          >coupling loop in about an inch or two from that so the coupling loop would
          >be 13.5in or so to 12.5in not sure which is better. was going to make the
          >"plate" to hold the cap out of lexan and the "plate" for the connections
          >back to the receiver. question is how many turns of wire for the AM BCB I am
          >sure there is a calc for this but I haven't seen it and I wanted to share my
          >design. Also the rest wood be made from wood the longer pieces.
          >
          >
          >Scott
          >KC7WDG

          My second post. I took a look at your construction schematic. U are using
          4 pegs sandwiched between 2 frames. My construction is similar but
          different. If you look at your schematic cross section (from the side) ...
          I have just one frame and the pegs are mounted with 1 screw each to only
          one frame. The other end of the peg is free. The frame I use is simply a
          plywood sheet (a plexiglass sheet and pegs would be classy). I mount my
          capacitor in the center on the opposite side of the sheet from the
          winding. I screw one end of a 12" peg on the same side of the sheet as the
          winding. I then slide my coupling coil (8" dia. 3 turns) along this peg
          for optimum coupling.

          I mount the whole thing vertically on a 8" square block which acts as a
          base. I glued a sheet of velvet material on the bottom to avoid scratching
          the HiFi set.

          For normal listening on the HiFi I just slide the pickup hoop right in the
          loop .... nothing critical. When I am dxing with another receiver I find
          the coupling adjustment is invaluable.


          Jim Dunstan
          Thunder Bay, ON
        • Bruce Carter
          I have built a couple of loops on styrofoam - they work great.
          Message 4 of 4 , Jul 27, 2004
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            I have built a couple of loops on styrofoam - they work great.
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