[Antennas] Metal roof interaction

Mon May 8 12:52:10 EDT 2006

Jon M. Knodel wrote:
>Hello,
>>I am getting ready to install my tower this summer and am looking for some help before I do. My house has a metal roof that I am afraid is going to interact with the antennas. 
>>I will be able to completely load the tower with all the antennas that I want to at the 40' height. This would put the top of the tower only about 25' above the metal roof. Is this close distance going to affect the antenna performance (3 element SteppIR yagi)? I can also sacrifice some antenna load and put the tower up to 60'. This would be the path I would take if the roof would interfere with the antenna at 40' (trading off antennas for additional height and less interaction with the metal roof).
>>So, my question is: how much would the roof interact with my antenna? Because it is a SteppIR and fully adjustable, is this a concern at all due to the fact that it can be retuned easily? Or would the radiation pattern be adversely affected? I appreciate all the help I can get. Thanks.
>>Jon, N7XW
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>>Of course the metal roof will have an effect on the antenna performance! A metal roof may be the ideal ground plane for a vertical antenna mounted thereon, but for other antennas not so. The effect or affect the roof will have will depend upon the frequency in use and vary with the azimuth to which the antenna is pointed. As one has suggested, you might try modeling to see how bad this may be. But my suggestion is to go ahead and put the antennas on the 40 foot tower. Nothing is ever perfect and those who seek perfection are spinning their wheels. That's what ham radio is all about: "cut and try." You may be pleasantly surprised and find you were worrying about (almost) nothing!
>Harvey/W4TG
>>