On 5/20/2010 1:51 AM, David Gilbert wrote:
> Instead of trying to base your decision on a bunch of anecdotal advice,
> why don't you use HFTA to evaluate various heights on your bands of
> interest for the signal paths you are primarily interested in. HFTA not
> only shows you the elevation pattern for the height you choose, it also
> provides a pseudo figure of merit that shows how well that pattern
> corresponds to the optimum takeoff angles (calculated over an entire
> sunspot cycle) for any path you select. It isn't prefect by any means,
> but it's a whole lot more objective than just about anything else,
> especially if you're mostly making comparisons between one option versus
> another.
HFTA is a great place to start, but that QST article some time in the
last couple of years did an excellent job of explaining the changing,
optimum take off angles throughout the sunspot cycles and then analyzing
them statistically . No specific height is best all the time and they
came up with a height that statistically was best "most often".
It appears that for most of us we'd never notice the difference between
50 and 70 feet and often the difference between optimum and any thing
else in that range is small. It might be enough to make a difference and
it might not.
If some one could find that article, then we'd have some good numbers to
work with.
73
Roger (K8RI)
> The program is free with the ARRL Antenna Book and is very
> easy to use, and if you live on flat terrain you don't even need to work
> up a special terrain description file.
>
> 73,
> Dave AB7E
>
>
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