Topband: radial layout and pattern skew

[Garry Shapiro]

I regret disagreeing with my friend Earl, but I just purchased and installed
EZNEC 4, and it, like EZNEC 3, uses the NEC-2 engine. EZNEC 4+ offers more
segments and a few additional features, but also utilizes NEC-2.

The offering that utilizes NEC-4 is EZNEC Pro, at a considerably higher
price, and requires purchase of a NEC-4 license before purchasing EZNEC Pro.

Given that, one would expect results from EZNEC 3 and EZNEC 4 to be very
close, as Earl stated, but unrelated to NEC-4 performance.

Garry, NI6T

-----Original Message-----
From: topband-bounces at contesting.com
[mailto:topband-bounces at contesting.com]On Behalf Of Earl W Cunningham
Sent: Sunday, September 05, 2004 7:15 PM
To: topband at contesting.com
Cc: kb8jvh at reydata.com; w8ji at contesting.com; eric at k3na.org
Subject: Re: Topband: radial layout and pattern skew


Tom, W8JI wrote:

"The common Eznec programs use NEC-2 engines, and there is considerable
question about accuracy of models with conductors near earth."
==========
In a comparison test I did a year or so ago, the results of EZNEC3 and
EZNEC4 (which uses the NEC-4 engine and can model in-ground radials) were
compared.  In EZNEC3, the radials were modeled slightly above ground and
in the NEC-4 program, they were modeled on (in contact with) the ground.
I was surprised at how closely the two programs agreed on patterns and
gain of the same antenna.

In EZNEC3, the high accuracy Sommerfield-Norton ground model was used and
in the program with the NEC-4 engine (modeling was done by the editor of
the ARRL Antenna Book, Dean Straw, N6BV), the high accuracy ground model
was used.

Therefore, if EZNEC3 (which uses the NEC-2 engine) was inaccurate, then
so was the program that used the NEC-4 engine.

73, de Earl, K6SE
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