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Thread: Request RF/Groundplane info

  1. #1
    CarlOrton's Avatar
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    Request RF/Groundplane info

    Hi, All;

    I'm trying to decide on where to place the transponder antenna. This is a "regular" pre-ADSB small monopole antenna. This is going on a Zenith Cruzer, all aluminum.

    My question is: How close to the edge of the structure may I place the antenna? IOW, I don't know if I need to have a minimum distance in each direction from the mounting hole, or is having plenty of room in the other 3 directions sufficient. I *know* a center-placed antenna would be better, I just don't know how much I lose with an edge-mounted antenna.

    Thanks for any info you provide!

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    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  2. #2
    FlyingRon's Avatar
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    A quick calculation would tend to indicate that 8 cm (just over 3") would be fine.

  3. #3
    CarlOrton's Avatar
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    Thank You, Ron; may I ask how that number was calculated (I know digital. RF, ehhhhhhhh.....)

    Carl Orton
    Sonex #1170 / Zenith 750 Cruzer
    http://mykitlog.com/corton

  4. #4
    FlyingRon's Avatar
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    A quarter-wave vertical (what you have here) needs a quarterwave counterpoise. A quarterwave at 1030MHz is about 29m (neglecting velocity issues). So a quarter of that plus a little more fudge for velocity factor.

  5. #5
    Scooper's Avatar
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    Quote Originally Posted by FlyingRon View Post
    A quarter-wave vertical (what you have here) needs a quarterwave counterpoise. A quarterwave at 1030MHz is about 29m (neglecting velocity issues). So a quarter of that plus a little more fudge for velocity factor.
    Ron, I think you mean a full wavelength at 1030 MHz is about 0.29 meters, so a quarter wavelength counterpoise would be 0.0725 meters, or 2.8543307 (~3) inches.
    - Stan, Private Pilot ASEL, LSR-I, EAA 115792 (since 1966), EAA Chapter 124
    Zenith CH601XLi-B, N601KE, KSTS



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