[TowerTalk] HFTA

[Jim Brown]

On Wed, 21 Apr 2010 23:23:23 EDT, Cqtestk4xs at 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