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Base antenna placement question

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KD5SFF, Jan 27, 2019.

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  1. KD5SFF

    KD5SFF Ham Member QRZ Page

    Hey all... Question from an inexperienced ham here...

    Due to HOA restrictions and needing to be a little stealthy, I’ve got two options to place my Arrow 2M/70cm ground plane antenna: (1) in the attic and then an approximate 30’ run of coax to my radio, or (2) outside on a mast but a coax run of approx 100’. Coax used is LMR 400. Antenna height would be similar with the outside mast about 5’ higher than what my attic would provide. I don’t have insulation with foil backing. Just insulated duct work.

    I know that outside is generally better, but at VHF/UHF frequencies, I’m a little unsure of how to balance the length of the coax, height of the antenna, and whether it’s inside/outside.

    Any suggestions, or considerations that maybe I’m not aware of?

  2. AA5CT

    AA5CT Ham Member QRZ Page

    Above the duct work would be good - give the antenna a good view I think might be a little better choice.

    Are you working mainly repeaters or direct/simplex?
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Outside should be better.

    100' of LMR400 only has about 1.5 dB loss on 2m, you won't even notice it.

    How RF "transparent" an attic is depends on more than just lack of foil backed insulation and height above ground (although those are surely considerations); the materials used in the home siding and exterior finishing as well as that of the roof are also important. If everything is just "wood" and nothing else -- not bad. Stucco, cement, brick and of course aluminum siding are bad. For roofing, thin asphalt shingles over tar paper and then wood isn't bad; cement tiles and some other materials are.

    Outside above the roof is almost always notably better.
    AG6QR and K7JEM like this.
  4. KD5SFF

    KD5SFF Ham Member QRZ Page

    Mostly repeaters. Simplex every now and then. Probably a 70-30 split.
  5. KD5SFF

    KD5SFF Ham Member QRZ Page

    It’s a typical suburban house in the Memphis area. Built in 2005. Typical building materials.

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