wrote in message
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I'm planning on building a 10 meter ground plane antenna out of PVC pipe
and #12 wire radials drooping about 40 degrees. This will be mounted on my
roof on a tripod and mast, with the radials also serving as guy wires. The
ARRL antenna book mentions that a ground plane antenna should be mounted at
least one half wavelength above "ground". I know that this sounds like a
stupid question but I have to ask: for this example do I consider the roof,
which is more than 5 meters above ground level as "ground" or do I need to
be at least 5 meters above the roof. I would like to secure the radials,
(guy wires) to my roof, but with the antenna at 5 meters high my droop
angle will be off and then I can't guarantee a 50 ohm match. The house is
wood frame, no foil backed insulation and a non metallic roof. Thanks for
any advice. Lenny

You can think of the ground as being the actual ground for your case. Even
if the roof was a conductor it would not be large enough to actually be
called the ground. Unless there conductors for several wavelenghts around
the antenna they usually have little effect on the antenna. if they are
below the radials.



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