Using the tin roof itself for the ground plane is rife with potential
connectivity problems.
Back in my Washington DC just out of college days I lived in a row house
block with parallel copper roofs couple hundred feet either direction up the
street. I mounted the antenna on a sewer vent pipe and put regular radials
suspended a foot or so above the roof. The results for that setup were
excellent. I used it on 40-10. I was severely disappointed when I took the
same physical setup and ran it just above sod at my suburban home a few
years later.
Use your building as a ground screen underneath but not connected to your
tuned radial system. Use a current block between the vertical/radial feed
and the feed coax. Ground the coax shield to the roof on the shack side of
the current block. Do not use the roof as an active part of the antenna.
73, Guy.
----- Original Message -----
From: "George Warnock" <george_warnock@hotmail.com>
To: <antennaware@contesting.com>
Sent: Friday, February 27, 2009 6:27 AM
Subject: [Antennaware] vertical with metal roof as groundplane
>
> Hello folks...am preparing the ground to build a workshop, when completed
> it will be 40 foot long by 30 foot wide, there will be a box profile tin
> roof, the pitch of the roof will be approx 20 degrees.There will be a
> metal truss in the centre of the roof to support metal purlins and then
> the roof its self....to me this sounds like a likely candiate to support a
> "support" for a 40m vert antenna and use the tin roof for a groundplane.I
> would be interested in what you folks think of the idea, and perhaps some
> one could see perhaps a way of taking even more advantage of the
> situation...am thinking along the lines of phased verticals perhaps with
> additional ground wires or antenna for 80m or 40/80....the only down side
> I can see is there is a tower about 50 feet from where the shed is going
> to be so that may have some interaction...the "mechanics" of bonding the
> individual sheets of tin together to form a ground plane will be taken
> care of during the build..
>
> reguards george
>
> gi0vgl...
>
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