Similar experience here. In a 30-year period we put various verticals on
the copper roof of the U.S. Senate Office Building (W3USS). The roof is
rectangular, about 225 feet to a side with a very large courtyard in the
middle. The verticals all worked great until sometime during the late
70's/early 80's when increasing computer-generated noise raised the noise
floor from S0 on ten meters (for example) to S7-9. Equivalent noise on
lower bands. During the daytime noise on 40 & 80 meters was S9+10-20 dB by
the late 1980's. Various noise reduction schemes and listening antenna
experiments were unsuccessful. This noise was in addition to the elevator
and air circulation motors all running in the attic and probably grounded
into the same circuit as the copper roof, 100 feet in the air.
Rectification in the copper sheet roof joints was a big problem too. One
day Senator Goldwater called me to ask why he was getting music and local
programming in the background of a 2 meter repeater frequency. It was from
an AM broadcast antenna located a couple thousand feet behind Union Station
operating at ~1400 KHz. I replaced the coax, making sure all the connectors
were completely soldered, but it persisted. It eventually went away, then
would come and go without apparent explanation over many years.
Operating 160 meter contests from there before sunset (when the AM station
either went QRT or amateur signals overpowered the AM signals) was quite an
experience too, more receiver-caused than rectification perhaps. The joys
of operating at an urban QTH! - Dave, K3ZJ
-----Original Message-----
From: Tom Osborne [mailto:w7why@harborside.com]
Sent: Thursday, May 31, 2001 10:15 PM
To: TowerTalk
Subject: Re: [TowerTalk] copper roofs?
K4IA@aol.com wrote:
>
> I have a tin roof on my house. I asked a lot of questions like >yours and
got darn few answers. I think no one really knows. >It definitely isn't
"ground" and you can't consider the roof a >monolith because there are
seams.
Hi All
A friend of mine, W7IVX, moved to a new QTH and until he got his
80 meter beam up, he was using a HF-2 on top of a metal roofed
barn. He tied the tin together with screws and it worked out
real well. Not as good as the 2 el. on a 180 foot tower, but
sufficient to work some good DX. Probably a lot better than a
dipole at the same height. 73
Tom W7WHY
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