I ran some quick models of a tower at the corner of a house with a metal roof in HFTA. The effects of the metal roof were modeled by a plane (sloping) from the tower to the edge of the roof, a drop from eave height to local ground height (set to flat for these purposes) and then flat ground out five miles.
While there is some change, the effects are minor and would be lost in the clutter of other terrain effects anyplace other than in the middle of a vast open plain. The biggest effect will be impedance changes as Mike noted - and they should me minimal if the antenna is 10 meters/30 feet or more above the roof level for 20 meters and and above. A low band wire will be a different story as the effective height will be quite low. 73, ... Joe, W4TV On 7/4/2013 5:05 PM, Mike Harris wrote:
I run an Optibeam OB9-5 at about 42 feet on a tower only 10 feet away from the corner of our single story house with metal roof. It hasn't disadvantaged me any. I see a small change in SWR as the larger elements of 20M and 17M swing over the roof. Regards, Mike VP8NO ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
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