"Richard Clark" wrote in message
...
On Sun, 21 May 2006 23:48:59 -0500, "AG4QC"
wrote:

I am having a metal roof put on the house and shop. The installer said it
isn't required to be grounded. The city inspector said the same thing. Is
that really true? I'm thinking of running a #8 from the roof to my common
ground. Does that make sense?

Hi Joe,

It is arguable that the entire roof would even be evenly conducting,
as installed. As conductivity is not a primary concern, the installer
is not motivated to insure that a #8 wire attached to one panel would
be felt by any other with any degree of confidence. Further, even if
all panels exhibited continuity today, this is not to say they would
tomorrow unless some care was taken to insure tight interconnections.

It is not unheard of here in this group to find Hams taking that care
and bonding all panels. The sense of it is to reduce the chance of
developing spurs due to RF currents meeting corroded joints (although,
no one has ever reported this as a problem, only anticipated it).

73's
Richard Clark, KB7QHC

Joe,
Another concern (though I have no experience with roofs, just autos) is the
intermitent contact (as opposed to a rectifying junction, as Richard points
out) that is possible. If there are joints that can make and break, say in
the wind, you may have noise generated. Chain-link fences would be
susceptable to this as well. Wether or not it produces noise in your
receiver, I would think, is rather unlikely, unless you were somewhere near
a broadcast station or another ham for reasons described next.
Interestingly enough, if the transmit antenna is reasonably close to the
roof, it would manifest itself as noise on your *transmitted* signal also,
but probably low enough such that those listeming to you would hear it.
I had some experience with this phenomenon with things like trunk lids and
motorcycle seat springs causing noise in the 150 MHz car phones of the past.
The transmitter illuminated the noisy joint and the czarrier was literally
modulated by this. The near-by noisy joint can be considered to be a
parasitic element in the transmit antenna system and therefore produce
low-level, but annoying amounts of noise modulation. It appears as
sidebands on the transmitter which duplicate the noise of the joint. This
in turn was wide-band exnogh to extend over to the receive frequency.
Because it was full duplex and both Tx and Rx were on the same antenna, it
was a noise problem in the receiver. Also why I believe it is a bad idea
to use a chain link fence as a counterpoise.

73, Steve, K9DCI