Topband: antennas close to ground

[K4SAV]

 From the information I have heard and the comparisons I have done on 
several occasions there is very little difference between NEC2 and NEC4 
for wires close to the ground.  Of course NEC2 won't handle anything 
below ground.  I don't know exactly what the lower limit of height is 
when NEC2 flames out.  However N6LF shows a plot in his article for a 
450 ft BOG 1 inch above ground.  His analysis was done in NEC4-2.  I can 
closely generate the same thing in NEC2.  The pattern is almost 
identical, with only a small difference in the elevation angle of that 
little low angle null in the back half of the pattern.  I got 1 dB less 
forward gain that he did and the RDF was 12, same as he got.  Close 
enough for me.

Jerry, K4SAV


On 5/14/2016 5:37 PM, Carl Luetzelschwab wrote:
> Mike W0BTU commented:
>
> "But I thought that it was a well-established fact that NO antenna modeling
> software does well with antennas close to the ground".
>
> Yes, I believe that's true with the NEC-2 computational engine. The NEC-2
> engine is readily available to the public.
>
> The NEC-4 computational engine addresses antennas very close to ground,
> buried antennas and antennas connected to non-perfect ground. The NEC-4
> engine requires a license from Lawrence Livermore National Labs - it is
> $300 for US Non-commercial entities. This does *not* include the antenna
> analysis software.
>
> N6LF used NEC-4.2 (with EZNEC Pro4 v6) in his article that I recently
> cited, and his results were very good for what he simulated and measured
> (one buried antenna, one antenna very close to ground and a vertical wire
> with a ground rod).
>
> Of course just having the NEC-4 engine doesn't guarantee success, as N6LF
> pointed out. You must have an accurate model of your ground conditions, you
> must obey the wire rules, you must have accurate dimensions for the
> antenna, and if it's wire you should include the insulation, too.
>
> That's my two cents worth.
>
> Carl K9LA
> _________________
> Topband Reflector Archives - http://www.contesting.com/_topband