Hi, My new home was constructed with steel shingles that have a fifty year warranty. While I'm happy to have a great roofing system, I'm a bit in the dark on the effect this will have on antennas that are mast-mounted off my roof. I wouldn't put a dipole going over my roof -- I'm sure the shingles would be terrible for that type of antenna. I'm wondering if there's any kind of antenna (a vertical perhaps) that might work well with the metal roof as a counterpoise? Any thoughts on what kind of antenna (HF) I can get on the roof that might utilize this unique aspect of my home? Or - should I avoid all roof mounts and just stick to putting something up on a mast in my backyard. Right now I'm running a Buckmaster 7 bander about 30 feet from my house, strung up on some low bushes and cactus and I need to get it off the ground. (Holes dug, poles/masts coming).
I'm guessing that the shingles are coated so there's electrical conduction between shingle tabs. If that's true, then you wouldn't be able to take advantage of using them as a counterpoise since you'd have to mechanically/electrically tie many of them together, something that wouldn't be easy to do. A vertical--with a proper roof mount and laid-out radials--gets my vote.
not to worry, like my metal roof they are capactivly coupled. just do it and stop silly worrying...!!!
Just try a little experiment. If you have a chimney, or a sturdy stand pipe, put up a temporary foot 20 meter 1/4 wave vertical. Build a small L network, 12 turns of # 12 spaced 1 wire diameter, and a 100 pf or better variable cap, and find the LC ratio that works. If you get a good match, try transmitting and get some signal reports. If everything works well, then your roof is gold, if you can't get a match, or have RF feedback, or the SWR changes a lot with the amount of power applied, then it's no good. Bottom line, if it works, a 25 foot vertical with an AH4, or similar wire tuner will give you great results on 80 through 10 meters. Otherwise, you need a Hy-Gain or Cushcraft antenna mounted above the roof.
W7DGJ wrote : " ..... Any thoughts on what kind of antenna (HF) I can get on the roof that might utilize this unique aspect of my home? ..... " My tin roof IS my antenna for wavelengths up into the 6-meter band : http://ki3u.byethost3.com/Radio-Phy...g/Tuning up the Brass Bedpost - KI3U Web.html But as I caution in the above, for the sake of safety it is best to attempt such arrangements only with solid experience at hand. Berj / KI3U
Thank you WF7A. My roof is constructed of a small flat roof with asphalt wrap over an outdoor patio, and a chimney that extends perhaps six feet up. I would consider the Hustler 6 bander mounted on the chimney with a tilt over from DXE for those high wind situations which we get in AZ. The small flat roof, about 12 x 12 ft square, is the only section I have access to. The rest of the roof is metal tile and requires people with special shoes and experience to repair or get on roof. It's also relatively flat, but dangerous to walk on because the shingles will bend. They are made of metal, but they have a asbestos coating on the top surface which makes them look attractive (looks like a normal Phoenix area tile roof). The antenna would have the roof as a counterpoise, perhaps six feet below the lower mast of the antenna, but only on 190-210 degrees or so. The other piece of that 360 degree radius would be my flat roof section. If the roof acts as a counterpoise, is there a problem with a missing section? I would equate this to a ground mounted Hygain with lots of radials coming off the bottom plate, but not in a complete 360 degree arc.
My first 10 meter contact, from San Diego to Florida, was made with an old CB mag mount antenna stuck to the roof of a metal storage shed, with a little help from a manual antenna tuner.
Your metal tile-looking roof should only be used to shed water. They are normally about 1 foot by 3 or 4 foot panels with a thick non-conducting coating, useless as a counterpoise. I certainly would not fasten anything to, or drill through ,to fasten anything to them. The ONLY purpose of a roof is to keep your house dry, not as part of an antenna! In 50 years of roofing, I've had to fix hundreds of leaks where home-owners "needed" something attached to their roof.
I disagree with HR. The metal roof would be a great counterpoise for a vertical antenna. I had one on a large metal roof barn at our previous QTH and it worked fine. I would avoid drilling onto the metal or doing anything else that would harm its primary purpose of keeping your house dry. But as a counterpoise it should work fine.
