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Hexbeam interaction with a OCF dipole

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  • rywessel
    All- I just raised my broadband hexbeam that I put together based on Leo s plans on my roof on a 10ft pole for a total height above ground of 35ft on one end
    Message 1 of 5 , Feb 1, 2012
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      All-

      I just raised my broadband hexbeam that I put together based on Leo's plans on my roof on a 10ft pole for a total height above ground of 35ft on one end and 30ft on the other (sloping lot).

      I have an 133ft OCF dipole mounted between two trees and the wire is within 5ft horizontally and about 3ft vertically above the hexbeam about half way from the end of the wire.

      Question- Could there be an adverse impact to the beam as a result of the proximity of the OCF wire? will grounding the wire OCF when not in use make a difference?

      thanks,

      Robin Wessel
      KF7TGI
    • mike_k2mk
      Hi Robin, It s probably difficult to model this situation so here s a non-scientific experiment you could try. Take SWR readings on 20 meters at different beam
      Message 2 of 5 , Feb 2, 2012
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        Hi Robin,

        It's probably difficult to model this situation so here's a non-scientific experiment you could try. Take SWR readings on 20 meters at different beam headings. If the SWR rises in one particular direction then the answer to your first question "could" be yes. If you could remove the dipole at this point you would be able to confirm this response.

        Then put the dipole back and try grounding the dipole to see if that has an impact.

        73,
        Mike K2MK

        --- In hex-beam@yahoogroups.com, "rywessel" <robin.wessel@...> wrote:
        >
        > All-
        >
        > I just raised my broadband hexbeam that I put together based on Leo's plans on my roof on a 10ft pole for a total height above ground of 35ft on one end and 30ft on the other (sloping lot).
        >
        > I have an 133ft OCF dipole mounted between two trees and the wire is within 5ft horizontally and about 3ft vertically above the hexbeam about half way from the end of the wire.
        >
        > Question- Could there be an adverse impact to the beam as a result of the proximity of the OCF wire? will grounding the wire OCF when not in use make a difference?
        >
        > thanks,
        >
        > Robin Wessel
        > KF7TGI
        >
      • Mike Williams
        Hello Robin and group; I have a dual band dipole strung just underneath my hex and it is only a few feet below the 10 meter elements. The dipole is for 20 and
        Message 3 of 5 , Feb 2, 2012
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          Hello Robin and group;

          I have a dual band dipole strung just underneath my hex and it is only a few feet below the 10 meter elements. The dipole is for 20 and 30 meters and I have not noticed a significant difference in performance or in the antenna analysis graphs using an AIM 470. If nothing else the dipole serves as a good reference to the performance of the hex in 2 azimuths and there is indeed a 1.5 to 2 S unit difference between the antennas on the common band of 20 meters.

          Good DX!


          73 de W4DL Mike

          [Non-text portions of this message have been removed]
        • Steve
          Robin, The most sensitive indication of interaction between the antennas is likely to be the *rearward* performance of the hexbeam; that s because you have
          Message 4 of 5 , Feb 2, 2012
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            Robin,

            The most sensitive indication of interaction between the antennas is likely to be the *rearward* performance of the hexbeam; that's because you have introduced another potentially resonant parasitic element in addition to the Reflector.

            One easy check would be to listen to a station off the back of the hexbeam and alternately short-circuit, terminate with 50 Ohms, and open-circuit, the OCFD feedline. If the station off the back of the hexbeam changes level as you do that, you know there is some interaction and you may be able to assess the practical impact of it. Check it with stations at different ranges and in different directions.

            Monitoring the hexbeam SWR or forward performance as you mis-terminate the OCFD might also show up any interaction, but they tend to be less sensitive indicators.

            73,
            Steve G3TXQ


            --- In hex-beam@yahoogroups.com, "rywessel" <robin.wessel@...> wrote:
            >
            > All-
            >
            > I just raised my broadband hexbeam that I put together based on Leo's plans on my roof on a 10ft pole for a total height above ground of 35ft on one end and 30ft on the other (sloping lot).
            >
            > I have an 133ft OCF dipole mounted between two trees and the wire is within 5ft horizontally and about 3ft vertically above the hexbeam about half way from the end of the wire.
            >
            > Question- Could there be an adverse impact to the beam as a result of the proximity of the OCF wire? will grounding the wire OCF when not in use make a difference?
            >
            > thanks,
            >
            > Robin Wessel
            > KF7TGI
            >
          • rywessel
            Thanks for the suggestions. I just ran a test with and without the OCFD raised. Using the SWR test, I did notice any difference in SWR with or without the OCFD
            Message 5 of 5 , Feb 2, 2012
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              Thanks for the suggestions.

              I just ran a test with and without the OCFD raised. Using the SWR test, I did notice any difference in SWR with or without the OCFD raised or shorted to ground.

              I did notice however a fairly dramatic change (up to 0.4 SWR) between North and South that I think can be explained by the fact that I live on sloped lot. If I extend out 40ft in each direction there is about a 15ft+ difference in elevation. I guess height above ground needs to be looked at as an average within a certain radius of the antenna.

              I'm sure one of you has a formula for figuring that one out!

              Have not done enough testing with real signals but I am getting hearing a decent F/B ratio.

              regards,

              Robin Wessel
              KF7TGI

              --- In hex-beam@yahoogroups.com, "Steve" <steve@...> wrote:
              >
              > Robin,
              >
              > The most sensitive indication of interaction between the antennas is likely to be the *rearward* performance of the hexbeam; that's because you have introduced another potentially resonant parasitic element in addition to the Reflector.
              >
              > One easy check would be to listen to a station off the back of the hexbeam and alternately short-circuit, terminate with 50 Ohms, and open-circuit, the OCFD feedline. If the station off the back of the hexbeam changes level as you do that, you know there is some interaction and you may be able to assess the practical impact of it. Check it with stations at different ranges and in different directions.
              >
              > Monitoring the hexbeam SWR or forward performance as you mis-terminate the OCFD might also show up any interaction, but they tend to be less sensitive indicators.
              >
              > 73,
              > Steve G3TXQ
              >
              >
              > --- In hex-beam@yahoogroups.com, "rywessel" <robin.wessel@> wrote:
              > >
              > > All-
              > >
              > > I just raised my broadband hexbeam that I put together based on Leo's plans on my roof on a 10ft pole for a total height above ground of 35ft on one end and 30ft on the other (sloping lot).
              > >
              > > I have an 133ft OCF dipole mounted between two trees and the wire is within 5ft horizontally and about 3ft vertically above the hexbeam about half way from the end of the wire.
              > >
              > > Question- Could there be an adverse impact to the beam as a result of the proximity of the OCF wire? will grounding the wire OCF when not in use make a difference?
              > >
              > > thanks,
              > >
              > > Robin Wessel
              > > KF7TGI
              > >
              >
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