[antennaware] Convergence problem with EZNEC

Eric Gustafson n7cl@mmsi.com
Wed, 19 Apr 2000 15:47:50 -0700

Hi Pete,

My experience regarding segmentation in EZNEC (NEC-2) with even
simple Yagis has been similar to LBs.  I normally set the
frequency to at least 3 times the operating frequency and then do
the auto segmentation to the conservative setting.  Then I run
the model at the actual operating frequency (of course).  This
has produced pretty good agreement between modeled and measured

Also, as you no doubt have already noticed, stacking stock
antennas is unlikely to produce optimum results (particularly in
regards to F/B) until the antennas are readjusted to account for
having been exposed to one another.

However, if you are modeling guys that connect to the tower,
there may be other problems that need a bit of mitigation.  Can
you expound a bit more on the details of the model?

1.  How is the tower structure represented in the model?
    (lattice, fat conductor, etc.)

2.  Any slopers attached to the tower?

3.  Guys connected to tower?

4.  Insulator broken conductive guys to large segments of
    non-conductive guy cable to make the breaks?

5.  Etc.

73, Eric  N7CL

>Date: Wed, 19 Apr 2000 00:42:15 +0000
>From: Pete Smith <n4zr@contesting.com>
>I am working with models of the Force 12 C-3, trying to model
>stacks and their potential interaction with guy wires and wire
>low-band arrays.
>The models I'm using include a simplified monotaper model (7
>wires) and one based on the physical antenna (57 wires).
>According to EZNEC, these can be "conservatively" run on 28 mhz
>with ~ 95 and 130 segments.  However, I find that the gain
>figures, in particular, don't start to converge until quite
>close to EZNEC's 500-segment limit - the difference can be 1-1.5
>dBi.  This gives me real pause for the accuracy of models using
>2-3 of these antennas plus other conductors in the vicinity, yet
>staying under EZNEC's ceiling.
>Anyone got any advice on how I might deal with this?
>73, Pete Smith N4ZR

FAQ on WWW:               http://www.contesting.com/antennaware-faq.html
Submissions:              antennaware@contesting.com
Administrative requests:  antennaware-REQUEST@contesting.com
Problems:                 owner-antennaware@contesting.com