[TowerTalk] radial geometry
Mon, 3 Sep 2001 20:49:38 -0400
> I am burying radials under the lawn so that I can feed the tower as a
> vertical. The tower is a few feet West of the house. I can easily run
> 30-40' radials from tower to the N, NE, E, SE and S but I can not run
> radials from SW through to NW because of the house.
> How much does the radial geometry affect the radiation pattern?
> Any suggestion how to deal with the radials that should be run where
> the house lies (of other than moving the house or tower :-)?
If you can't go through the crawl or basement, just go around the
house with a heavy buss strap or wire. Pick up on the other side if
Radial geometry mostly affects overall efficiency, NOT pattern. It is
folklore that radials concentrated in one direction improve gain in
that direction a noticeable amount. The exception is if you make
the radials many wavelengths long and very very dense well out in
the Fresnel (fre-nell) zone.
I remember getting a call to a unstable BC array in Ann Arbor
Michigan. The pattern was weak in all directions, and unstable with
Turned out an engineer who measured excessive FS in the null
directions removed all the radials in those directions from a multiple
tower array. The result was FS in the desired directions dropped as
much as in the directions where he pulled out the radials.
Re-installing the ground system in the null directions brought back
the signal in all directions, and changing a bad component in the
phase monitor corrected the original problem. In 1970 dollars that
was an $4000 mistake.
73, Tom W8JI
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