>
> Assuming there is a LOT of metal in / near the roof, the
> effective height of the dipoles OVER the roof will be the
> height above the roof, i.e., it would be good to have 30 ft
> masts for support which will reduce coupling effects to
> the structural metal while still directing the signal UP for
> high angle local coverage.
Tom's right.
The antenna to use in that situation is a vertical. I had an R-7, a A3S,
and a G5RV above a tin roof on a 14 story building in Moscow. The G5RV was
useless, and the R-7 was in many cases equal to the A3S and was a killer on
40M. I did a lot of A-B testing and finally determined that the tin roof
worked as a great ground plane for the R-7 and effectively made the A3S
think it was 15' above ground. The G5RV never had a chance.
Jon Hamlet, W4ZW
Casey Key Island, FL
"A little bit of Paradise in the Gulf of Mexico"
One of the W1AW/4 Crew - IARU/WRTC-2000
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