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Is it possible to install a hex beam above a yagi without taking the yagi down?

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  • shaynal01
    At our club station we have a tri-band yagi at the top of a 60 foot tower. The yagi is mounted on a mast right above the rotator. The mast continues for about
    Message 1 of 3 , Jun 28, 2012
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      At our club station we have a tri-band yagi at the top of a 60 foot tower. The yagi is mounted on a mast right above the rotator. The mast continues for about two meters and there is a 2M vertical on the end of the mast. I would like to build and install a diy 6/12/17M hex beam above the yagi but below the 2M vertical using the existing mast. Are there any ideas for constructing a base plate that I can attach to the existing mast? Am I dreaming to think that I can do the installation and some final assembly without taking the yagi and mast down?
    • KE7ZAG
      This is a highly subjective answer because I do not know enough about the existing installation or how you intend to take the hex up the tower, but assume you
      Message 2 of 3 , Jul 2, 2012
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        This is a highly subjective answer because I do not know enough about the existing installation or how you intend to take the hex up the tower, but assume you are using a man lift or tilting the tower. A hex is light but bulky.

        I also assume you have an aluminum tri-bander and do not intend to operate the hex and tri-bander simultaneously.

        If you have a non-conductive tri-bander yagi such as a Spiderbeam, and do not ground the coax on it when the hex is being used, then I would approach it somewhat differently than what I say below.

        I would suspect you can install a 6/12/17 hex above the tri-bander without much ado. Efficiency of the hex will be limited by how close to a conductive structure of the tri-bander it is placed.

        Obviously, you will be operating inside the envelope of either antenna unless you extend the mast a considerable amount, but with the tri-bander (which I assume 20 meters is the lowest frequency) at 60 feet it will not see the hex sitting on top at a reasonable elevation above, as long as the hex does not have the coax nailed to the ground in the shack which is what some coax switches do.

        If the hex will be at less than an optimal minimum elevation above the metal tri-bander, under 26 feet (17 meters as the lowest band) above the tri-bander; it will then see the tri-bander as a ground plane and have a less than desirable take-off angle.

        If the tri-bander is a non-conductive Spiderbeam, or one of those home brewed X-beam variants, with an ungrounded coax, the hex will see the wire elements same as trees with little impact on take-off angle.

        As far as putting the 2 meter on top of a hex, that is not a good plan in my experience. I would use a stand-off and put the vertical down below the tri-bander. Reason being is that a metal mast in the element termination post on a hex has never worked well for me. I have tried the hex with the stainless element termination strap, and it has never performed even close to how the versions with a fiberglass or PVC support do.

        But, as I say, that is my experience and I expect a lot from my antennas or they come down and hit the scrap pile.

        73's

        Randy

        --- In hex-beam@yahoogroups.com, "shaynal01" <steve@...> wrote:
        >
        > At our club station we have a tri-band yagi at the top of a 60 foot tower. The yagi is mounted on a mast right above the rotator. The mast continues for about two meters and there is a 2M vertical on the end of the mast. I would like to build and install a diy 6/12/17M hex beam above the yagi but below the 2M vertical using the existing mast. Are there any ideas for constructing a base plate that I can attach to the existing mast? Am I dreaming to think that I can do the installation and some final assembly without taking the yagi and mast down?
        >
      • John Huggins
        ... Without addressing the near-field effects of such an arrangement, mechanically it is possible to put the hex between two other antennas if you offset the
        Message 3 of 3 , Jul 2, 2012
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          On 6/28/12 3:18 AM, shaynal01 wrote:
          >
          > At our club station we have a tri-band yagi at the top of a 60 foot
          > tower. The yagi is mounted on a mast right above the rotator. The mast
          > continues for about two meters and there is a 2M vertical on the end
          > of the mast. I would like to build and install a diy 6/12/17M hex beam
          > above the yagi but below the 2M vertical using the existing mast. Are
          > there any ideas for constructing a base plate that I can attach to the
          > existing mast? Am I dreaming to think that I can do the installation
          > and some final assembly without taking the yagi and mast down?
          >
          Without addressing the near-field effects of such an arrangement,
          mechanically it is possible to put the hex between two other antennas if
          you offset the feeder. Look at my site's article "Hexbeam Gets a Spine"...

          http://www.hamradio.me/antennas/hexbeam-gets-a-spine.html

          ...for ideas.

          >
          >




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