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Beam Antenna over metal roof?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WS4K, Aug 14, 2020.

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  1. WS4K

    WS4K Ham Member QRZ Page

    Have any of you experienced problems installing a beam over a house with a metal roof?

    My current house, here in central Florida, has a metal roof. I am hoping to install a Rohn 45 or 55 tower which can only be bracketed at the 9 foot level. This will limit my height above the bracket to only 30, maybe 35 feet. That means a total height of 40 or 45 feet. The highest peak in the roof is 22 feet high. Thus the beam would be 18 or 23 feet above the highest part of the roof.

    The antenna is a Mosley TA33M 3 element beam. Mosley was concerned I may experience "ground effect" if the antenna is not at least 20 to 30 feet above the roof. I contacted the ARRL Tech Dept. They have not dealt with this before and had no opinion.

    Does anyone have experience with antenna installation of beams above a metal roof?

    Eric WS4K
     
  2. AI5DH

    AI5DH Ham Member

    Eric all directional antennas must have proper clearance to operate properly. Two things that most hams fail to do is give antennas proper clearance. You gotta be at least 1/2 wavelength above earth or anything acting as earth like a tin roof and 2 wavelengths away from the shack. Otherwise you end up like most hams, with a compromised antenna. That is why hams got HF, no one wants to deal with the antenna size and limited bandwidth.
     
    N5YPJ likes this.
  3. ND6M

    ND6M Ham Member QRZ Page

    Tell me it ain't so.
     
    KB0MNM and N5YPJ like this.
  4. W1VT

    W1VT Ham Member QRZ Page

    "Sent: Monday, December 22, 2014 9:18 AM
    To: Eric Kennard
    Cc: Sarratt, Greg
    Subject: RE: Will a metal roof affect antennas


    Hi Eric WS4K,

    A large metal roof can make it hard to tune a nearby 40 or 80 meter wire antenna to resonance. With half wavelength or more spacing between the roof and the beam, the interaction usually isn’t a problem.

    At the HQ club—the 80M antenna is hard to tune—the SWR is OK, not great, --we use an antenna tuner. The beam works great. With typical house sizes, you are likely to have an issue on 40 rather than 80."
     
    KB0MNM and N0TZU like this.
  5. KL7SG

    KL7SG Platinum Subscriber Platinum Subscriber QRZ Page

    This won't be an ideal installation; but, it will work ok.
    At my QTH, I am running a TH7 yagi at about 35 feet with a metal building about 20 feet away.
    Not the best situation -- but it works OK.
     
    K0UO and N0TZU like this.
  6. KD0CAC

    KD0CAC Ham Member QRZ Page

    Seems like the HQ club & you are talking the old apples/oranges game - 40-80m / 20m .
     
  7. WW2PT

    WW2PT Ham Member QRZ Page

    It will work a thousand times better than no antenna at all.
     
    N1VAU, KK4NSF, WA8FOZ and 7 others like this.
  8. WR2E

    WR2E Ham Member QRZ Page

    What's the other? Count correctly?
     
    KK4NSF, NB4R, K5WY and 3 others like this.
  9. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    :D
     
  10. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Put it up get on the air/ "The best antenna is one that's In the air and more importantly On the AIR"

    It's amateur radio we're not looking at the best angle radiation all the time, amateurs are scattered in all different directions and distances from you.
    Have fun
     
    N0TZU and KL7SG like this.

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