[TowerTalk] Radiation angle

[Jim Lux]

At 07:53 PM 12/8/2005, K4SAV wrote:
>The two largest factors affecting the take-off angle of a horizontal
>dipole are the height above ground and the terrain surrounding your
>antenna. NEC based and similar programs will give you information on
>antenna efficiency and take-off angle over flat ground but they won't
>handle the terrain question. The only program I know of that handles the
>terrain is HFTA, but there may be others that I don't know about.  If
>you live in rugged terrain, or have sloping ground close by, it is
>possible that this can have a larger effect than the height directly
>under the antenna.

Jerry brings up a very good point.. NEC will give you the antenna pattern, 
but doesn't deal with far field effects.  Not only uneven terrain, but 
varying soil properties, not to mention houses, trees, etc.

This too has been studied by hundreds, if not thousands, and there are 
modeling programs to deal with it. HFTA handles horizontally polarized 
antennas with uneven terrain with uniform soil properties.  There are other 
codes for more complex problems.  Jim Breakall used NEC-BSC from Ohio State 
to deal with the variable soil properties AND uneven terrain.

I think Jerry is basically right that there aren't any programs suitable 
for amateur radio use other than HFTA for this problem.  The other codes 
are either wretchedly expensive and require a lot of work to enter the 
model, or are just little pieces of the overall analysis, and you'd have a 
heap of software work in front of you to do it all.