A quad is three dimensional. With the quad boom at roughly 18 feet, the
spiders would drop 14-16 feet or so below that so the roof would be more
like 2-4 feet below the wire on 20 meters. Have you considered the Hex beam?
It would be up and away form the roof much better than a standard or
gem-type quad.
Mike, k5wmg
Pipe Creek, Texas
Fast cars, slow boats, big dogs, and summers off to write
On Wed, Apr 21, 2010 at 2:34 AM, Jon Knodel <jknodel@msn.com> wrote:
>
> I am looking at putting up a decent hf antenna on my 17.5' Glen Martin roof
> tower. Apart from yagis, I'm thinking about a Gem Quad or standard 2
> element quad. My question is, how much interaction with the roof will I
> have and how much will it degrade performance with the bottom of the loops
> being so close to the roof? I figure the bottom of the 20m loop will be
> roughly 8' above the roof. The house is typical wood construction with
> asphalt shingle roofing. I've been modeling with EZNEC and can accept the
> compromise in overall height (take off angle, etc.) but am just not sure
> what effect the close proximity with the roof will have. Any help is
> appreciated. Thanks.
>
>
>
> N7XW
>
>
>
>
>
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