On Wed, 21 Apr 2010 23:23:23 EDT, Cqtestk4xs@aol.com wrote:
>There is one warning about HFTA that everyone who uses it should know.
>N6BV says that it can give false gain readings if the antennas are to close
>to each other (less than 1/2 wavelength). Obviously, the 3 meter separation
>is way less than 1/2 wavelength.
Yes. The fundamental answer is that HFTA models only one thing -- how an
antenna
at a given height interacts with terrain. It can do that for several antennas
at
different heights, but as I understand it, HFTA does not consider the
relationship
between the antennas, only their individual relationships to terrain.
In the real world, the fields radiated by each antenna will have time, phase,
and
spatial relationships to each other IN EACH DIRECTION AND ELEVATION that will
combine in rather complex ways to modify their directional patterns. It takes
software like NEC to model that.
73,
Jim K9YC
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