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Antenna on Roof with Metal (Steel) Shingles

Discussion in 'Ham Radio Discussions' started by W7DGJ, Dec 28, 2020.

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  1. WF7A

    WF7A Subscriber QRZ Page

    Oops, typo: I should've typed " there's _no_ electrical conduction between shingle tabs." Sorry 'bout that.

    Sorry, Jerry, but I agree with HR--there's a BIG difference between a "real" metal roof (say, using corrugated steel) and a metal roof made of coated, non-conductive, steel shingles; with the former, it'd be worth it to tack weld bonding straps so you'd have a phenomenal counterpoise, but with the latter--bad idea, let alone impractical. However, a properly installed roof mount for a vertical is well worth it!

    'DGJ: I'm surprised asbestos is still used anywhere--interesting! As for a counterpoise, nothing says that radials have to radiate away straight out like daisy petals for it to be effective--you can wind them any which way. True, the counterpoise would be more effective if it radiated outward like a daisy, but you're in a compromise situation, anyway, so just do what you can by laying down fair number of them that'll conform to the shape of the roof. (Don't ask me how many--that, I don't know. There's a practical minimum number of radials for a counterpoise to be effective, but I'm sure a wisened ham here can clue us in on that (for a compromised installation like yours.))

    BTW: I used to live in Douglas, AZ, so I know your pain when it comes to heat out there.
    Last edited: Dec 29, 2020
  2. N7WR

    N7WR Premium Subscriber QRZ Page

    I may have misread it...I thought he had a conductive metal roof. If not then I do agree with you and HR. Sorry about that
    NL7W and WF7A like this.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Why? Bet the issue is not what you think.

    No different than placing over dirt. The killer of any dipole is not getting it up 1/2 wavelength above either dirt. or something in place of dirt like a metal roof acting as dirt. If you can get the dipole high enough makes no difference.
    KA4DPO likes this.
  4. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    I wouldn't drill into it either, so how do you suggest he connect the return path to the counterpoise?
  5. N7WR

    N7WR Premium Subscriber QRZ Page

    After re-reading the OP his roof does not seem suitable as a groundplane since there is no electrical connection between panels. If there was such a connection and the roof was suitable as a groundplane I would do what I did with my metal barn roof (which I did not want to drill into). I made the ground connection right at the end of the roof where the metal panels extended beyond the roof itself by a couple of inches. Drilled a hole there which had no negative effect on the water tight integrity of the roof.....but that doesn't apply in this case
    NL7W and KA4DPO like this.
  6. K5WY

    K5WY Premium Subscriber QRZ Page

    You didn't ask me, but I would just lay GP wires on the roof. They'll couple to some degree to the metal underneath.
    KA4DPO likes this.
  7. KA4DPO

    KA4DPO Platinum Subscriber Platinum Subscriber QRZ Page

    Unfortunately, they will no longer be resonant if you do that. I could, introduce unwanted radiation into the house electrical system also, kind of like laying a bunch of capacitive plates on the roof.

    Best bet would be to get a vertical as high abouve the roof as is practical, and either run quarter wave radials for each band (a ground plane), or use a GAP or similar vertical that does not need radials. Such antennas should also be elevated above the roof as much as possible.
    NL7W likes this.
  8. K5WY

    K5WY Premium Subscriber QRZ Page

    Absolutely true.

    Also true, although the one time I tried it it didn't seem to, or at least I never noticed any problem.

    That would probably work best, but it is more work. I'd try the easy way first and see how it does. :)
    KA4DPO likes this.
  9. W9WQA

    W9WQA Ham Member QRZ Page

    you have heard of insulated metal plates coupling energy from one to the other even in a vacuum huh..

    and i think we have screwed something to a roof with good sealer and had no leaks.
    what is all this PARANOID terror about mounting an antenna on a roof...?

    i put up hundreds of tv antennas on tripods on roofs
  10. NL7W

    NL7W Ham Member QRZ Page

    This is the sure-fire way to skin the cat... so to speak.

    Perusing this thread, I also missed this roof being different from those metal roofs I've known in the past.
    KA4DPO likes this.

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