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Spacing between multiple ADS-B antennas

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  • Spacing between multiple ADS-B antennas

    I'm looking at constructions to install two ADS-B antennas above my TV antenna.
    As the (for now) antennas need to function without interference from one another or the TV antenna I searched of the forum and found this very helpful post

    Originally posted by paradiselost View Post
    Noel, ADS-B and other receiving antennas can coexist on the same mast provided the ADS-B antenna either stands off from the mast or is placed at the very top with the tv antenna mounted below. TV signals are horizontally polarized where as ADS-B signals are vertically polarized.

    ...

    In the case of multiple ADS-B antennas on the same horizontal plane I use a tee with a 12" nipple on either side to stand off from the top of the mast terminating into another tee with each having a 12" nipple, elbow and a capped 12" vertical nipple to attach the antenna. This type of arrangement will accommodate 4 or more antennas, spaced two foot apart, that will peacefully co-exist with no interference in line of sight.
    It's clear that the ADS-B antenna needs to be above the TV antenna, but it's unclear to me what the ideal minimal distance between two ADS-B antenna's in the same horizontal plane should be.
    I found that Spacing > (wavelength(lambda)/2) [= ~ 6 cm]but is there like an ideal distance in your experience?
    F-SMZO2

  • #2
    I have no interaction between these 2 antennas. One is a 3.5 element coco and the other is a 8.5 element coco. Space them as far apart as you can...

    http://ads-b.ca/antenna-collinear-F-CYYZ2/img_9687.htm

    I have a UHF TV antenna above the ADS-B, but it's far enough away to also not cause any interference.

    http://ads-b.ca/LDF1-50-super-antenna/img_9686.htm
    www.ADS-B.ca

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    • #3
      Thanks.

      I scrubbed the plan to place the receiver on the TV antenna mast.
      Now planning to erect a 20ft pole for my ADS-B receivers.
      F-SMZO2

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      • #4
        Hi, first of all I'm kind of the intimidated by the proffessionalism of the home made setups seen here .
        Anyway, I made my own DIY antenna by (sort of) following the balard's tutorial (not allowed to post links).
        The antenna, tested on the window, had some decent performance, but of course I was limited by house walls, so I decided to mount it on the roof.
        Now, it is performing very poorly. Might the problem be siting related? The DVB stick is placed inside the antenna (as it was when tested on the window).
        IMG-20150704-WA0012.jpg
        On the same mast I have the wind vane and anemometer of my PWS, and a UHF digital TV Yagi antenna. The mast is metallic.
        Any help is appreciated - please don't make fun of my very amateur setup!
        Last edited by maaw; 2015-07-05, 14:37.

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        • #5
          The spacing between the antenna and the pole looks like 100-150mm
          At that spacing, the radiation pattern will be altered and no longer omnidirectional.
          I would try mounting the antenna 500mm or more from the pole and use insulated supports. A support at the bottom, below the antenna elements can be metalic.

          You might also be suffering from interference now the antenna is better located.
          A long USB cable can have problems too. Use clip-on ferrite suppressors on both ends.

          Jim

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          • #6
            Originally posted by TassyJim View Post
            The spacing between the antenna and the pole looks like 100-150mm
            At that spacing, the radiation pattern will be altered and no longer omnidirectional.
            I would try mounting the antenna 500mm or more from the pole and use insulated supports. A support at the bottom, below the antenna elements can be metalic.

            You might also be suffering from interference now the antenna is better located.
            A long USB cable can have problems too. Use clip-on ferrite suppressors on both ends.

            Jim
            Thank you very much Jim, your answer was very elegant and kind of comforting. I was very frustrated.
            The spacing is indeed less than that (about 50mm), but the USB wire is short (1.5m standard extender), because I have a TP-Link MR3020 mounted externally under the roof.
            I will make some modifications and post again, so that everyone can get benefited from this trial and error.
            Cheers.

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