At 09:16 PM 7/17/03 -0800, Paul Carr wrote:
>I want to install a vertical antenna on a structure with a metal roof
>using a tripod. What are the issues with mounting a vertical in this fashion?
>
>Does the antenna need to be mounted a certain height above the metal
>roof? Should the base of the antenna be grounded to the roof or should I
>strive for isolation? Can anyone describe actual installations?
I assume that "insulated" radials will be required.
I have an HF-9V vertical mounted above a galvanized roof. I used two
8-foot 1X6s, crossed, with a pipe flange and about 2 feet of pipe - the
antenna's base section simply drops into the pipe. The resulting base is
quite stable with this 26-foot-tall antenna.
Although I was told that I should use resonant radials, what I did instead
(the roof is about 30 x 16 feet, 10-12 feet above ground) was to use two
125-foot wires attached to the ground side of the antenna, laid on the roof
so as to couple to each section of roofing material. I also connected the
ground side directly to the roof. I don't doubt that a couple of resonant
radials would probably make a better counterpoise for 80 meters, but I
didn't do that.
The antenna is used chiefly as a second radio antenna for contesting. It's
no great shakes compared to my primary antennas, but in a couple of
contests last fall (CQWW and SS, both CW) I think I worked everything I
called with it (and 100 watts), including a number of Europeans. I was
pleasantly surprised.
73, Pete N4ZR
The World HF Contest Station Database was updated 17 June 03.
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