A metal garage roof is not likely to affect beam performance with a 60'
vertical spacing and the small area involved.
However, careful attention to bonding the material into a single sheet
(electrically) can save some problems as the material ages. Aluminum
sides as it grows older can form "diode junction" contacts between points
and edges on one piece and surfaces on the next. The results can be all
manner of received signals from local sources, premixed at the siding and
reradiated to the antenna. Transmitted signals may also show up in
strange places, from VLF to VHF. I went through this process in a rented
house back in the 1960s, and the siding was only a few years old.
I cannot speak to current materials for metal siding and roofing, but the
general recommendation for careful electrical bonding seems to be one of
the safer precautions--and something easier done at installation than
later.
Hope this is useful.
-73-
LB, W4RNL
L. B. Cebik, W4RNL /\ /\ * / / / Tel: (423) 938-6335
1434 High Mesa Drive / \/ \/\ ----/\---
Knoxville, Tennessee /\ \ \ \ / / || / http://www.cebik.com
37938-4443 USA / \ \ \ \ || e-mail: cebik@utk.edu
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