Yes, by all means, look at the descriptions in the Antenna Book and on
the ARRL web site. I'm not sure if it is mentioned there, but there's
one added consideration. I think I'm correct to describe HFTA and its
predecessors as two-dimensional - that is, in calculating the effects of
terrain on a signal being radiated on a given azimuth, the program only
considers reflection and diffraction occurring *in the plane* defined by
the azimuth and the tower base. Any effects from terrain that slopes
*across* the plane are not calculated. I have no idea, in practice, how
large such effects might be, but it seems worth bringing up. I can
visualize "funneling" effects that could result from a signal passing
through a steep-sided deep valley between two mountains, for example.
73, Pete N4ZR
On 4/25/2010 9:31 AM, Jim Brown wrote:
> On Sun, 25 Apr 2010 03:55:08 -0500, Barry Merrill wrote:
>
>
>> Since you brought it up, what is HFTa'S
>> optimum slope angle and distance for maximum gain?
>> I assume it's different for each HF band?
>>
> Study the discussion of HFTA in the ARRL Antenna Book.
>
> 73,
>
> Jim K9YC
>
>
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