Paul,
I tried an 80m vertical dipole with its tip just 1ft above ground. Of
course the TO angles are generally lower than the quarter-wave because
of the increased vertical dimension. The results pretty much followed
what you would predict from a simple comparison with the quarter-wave,
although the changed current distribution causes some detail differences.
The TO angle began to drop once the Salt water medium extended 300ft
from the base, and the improvement had pretty much "run its course" at
1000ft. Roughly twice the distances of the quarter-wave.
Perhaps the most interesting feature was an *increase* in TO angle (by
about 4 degrees) when the Salt water medium was in the range 100ft to 300ft.
73,
Steve G3TXQ
On 08/01/2011 11:50, Paul Christensen wrote:
>> http://www.karinya.net/g3txq/temp/ground_zones_2.png
> Steve,
>
> Do you know if the elevation chart would change much if instead of a
> ground-mounted 80m quarter-wave vertical, a half-wave vertical dipole was
> used ? The maximum current point would rise a quarter wave above the ground
> and the Fresnel geometry would seem to change, albeit slightly in relation
> to the horizontal distance.
>
> Paul, W9AC
>
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