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Re: [loopantennas] Re: Fm question

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  • sonicxcove@aol.com
    Nice Jim, Size wise the quads are hard to beat. I love the pipe wrench rotator! After my heart there. I am awaiting some nice weather to see what I can come up
    Message 1 of 22 , Mar 31, 2008
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      Nice Jim,

      Size wise the quads are hard to beat. I love the pipe wrench
      rotator! After my heart there. I am awaiting some nice weather
      to see what I can come up with for antennas. I have lots of TV
      mast and 1000' of polyester rope to hold things steady. Never
      built an HF quad to date, but plan on that too. I have toyed with
      them on VHF though. Nice.

      By high maintenance was that due to the bamboo or wire breakage?
      Was not too much of an issue with VHF, but a lot less flexure there.

      I have seen some designs where they preload the spreaders with the
      wire to bow them which eliminates some of the problems. That would
      add more stress to the wire tough. Having been there let me know
      what you think.

      Last good cycle I was building a Ten-Tec six meter FM transceiver
      and the instructions for pre-aligning the receiver section called for you
      to tune into the strongest station that you could find. Found one that
      sounded to be a local. Shoot, He was in Florida and I am in Ohio.
      Picture me with this radio with no complete transmit section yet!
      Glad that is not on film.

      Thanks for the post,

      Eric --KB8TJR

      In a message dated 3/31/2008 10:59:39 P.M. Eastern Daylight Time,
      jdunstan@... writes:

      Hi Eric,

      I built a cubical quad for 20/15 back in the late 50's or early 60's using
      bamboo ... which was used in shipping carpets. It sat on a guyed 30' TV
      mast which i rotated with a pipe wrench. It worked DX like you wouldn't
      believe .... but then that was at the peak of the all time best sunspot
      cycle hi hi However conditions aside ... the quad was one of the nicest
      HF antenna I ever used (but then I have had the privilege of using a large
      rhombic) .... it was quiet, broad band (xmitter liked it) and signals just
      jumped right out. The problem was it was rather high maintenance.

      Jim, VE3CI







      **************Create a Home Theater Like the Pros. Watch the video on AOL
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      [Non-text portions of this message have been removed]
    • Jim Dunstan
      ... Hi, As with most things when you go big everything is magnified .... a quad for 20m is approx. 17 per side. I arranged the spreaders so they would be on
      Message 2 of 22 , Apr 1 9:15 AM
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        At 11:29 PM 3/31/2008 -0400, you wrote:


        >Nice Jim,
        >
        >Size wise the quads are hard to beat. I love the pipe wrench
        >rotator! After my heart there. I am awaiting some nice weather
        >to see what I can come up with for antennas. I have lots of TV
        >mast and 1000' of polyester rope to hold things steady. Never
        >built an HF quad to date, but plan on that too. I have toyed with
        >them on VHF though. Nice.
        >
        >By high maintenance was that due to the bamboo or wire breakage?
        >Was not too much of an issue with VHF, but a lot less flexure there.

        Hi,

        As with most things when you go big everything is magnified .... a quad for
        20m is approx. 17' per side. I arranged the spreaders so they would be on
        a 45 deg angle to either the vertical or horizontal plane. The distance
        from the center to each corner is exactly 12'. I tied on small metal
        fittings to the ends and spread thin flexible braided type copper wire
        around the 4 corners (approx. 68' total) ... I fed the center of the bottom
        horizontal portion with 72 ohm balanced line. The 72 ohm balanced line
        (they don't make it any more as far as I know) came down to the shack and a
        1:1 voltage balun (made by Heathkit from air-dux coils).

        It was a perfect match ... and the antenna will take any legal level of
        power you would wish to put to it.

        I used approx 6' to 8' for an aluminium boom. I used a second loop as a
        reflector ... and tuned it with a piece of open wire line for maximum front
        to back ratio. I later mounted a second set of loops within the first loop
        for 15 m and fed it from the same feed point with the same feed line. I
        never noted any deterioration in performance.

        The only maintenance problem was ICE .... the antenna was very gud in the
        wind, but if there should be freezing rain with a build up of ice load the
        whole thing will droop like a wilted flower. The other problem was general
        weathering of the bamboo ... eg getting dry and brittle over time. The
        whole thing is quite light.

        The spreaders in this arrangement are not under much tension. I used home
        brew flanges at each end of the boom to clamp the 4 bamboo poles for each
        loop. The tricky part is building this thing and then getting it up
        there. My 30' tv mast was made of 3 pieces that would nest together. I
        could build and adjust the antenna on the top of the 10' piece then push it
        up by hand. the bottom of the mast sat in a smooth cup on the base ... and
        the guys were attached to rings that allowed the mast to turn. so the only
        thing holding the antenna from turning was the friction in the cup at the
        base. The 2' pipe wrench was more than enough to rotate the whole
        mast/antenna assembly.

        The quad worked very well on 20m at 30' height. A friend of mine had a
        quad on a 60 ft tower (a commercial quad ... GEM quad) and it was exceptional.

        Jim, VE3CI
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