[Antennaware] Re: NVIS -- modeling, mininec vs nec-2 disparity

[Pete Smith]

At 09:51 PM 6/6/02 -0400, Guy Olinger, K2AV wrote:
>Going to post this to antennaware, with the figures to see if the
>gatheren already know about this.
>
>The antenna in question...two element reflector beam pointing straight
>up.
>
>7.025 MHz, upper wire fed in center
>
>Upper wire = 67.5 feet long, 47.7 feet high (21 segs on eznec, 16
>segs/hw mininec)
>Lower wire = 68.4 feet long, 7.4 feet high
>
>AO (mininec) optimizes to these numbers, gets 11 dbi at 75 degrees
>with 11.4 dbi straight up.
>
>Anyone know about this one and care to comment?

I'm not sure how much of the context was on the reflector, so let me just 
add a little.  The same model, with NEC-2 and Sommerfeld-Norton ground, 
shows a VERY different result.  Instead of peak gain being at the zenith, 
it is at 41 degrees and maximum is only 5.99 dBi.  With what EZNEC calls 
MiniNEC ground, results from NEC-2 are close to those Guy reports from 
AO.  Since doubling the number of segments produces very little change in 
these results, I presume they represent good convergence.

The question is, which modeling result is closer to reality?


73, Pete N4ZR