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Old September 24th 08, 06:35 AM posted to rec.radio.amateur.antenna
Jeff Liebermann[_2_] Jeff Liebermann[_2_] is offline
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First recorded activity by RadioBanter: Jun 2007
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Default Help with slim jim nec model

On Tue, 23 Sep 2008 19:09:10 -0700 (PDT), Art Unwin
wrote:

Incidentally, MMANA-GAL Yahoo Group:
http://groups.yahoo.com/group/MM-HAMSOFT/


Does this have unlimited segments and variableswith it's optimizer?


I couldn't find any documentation as to the program limits. As I
understand it, MMANA-GAL has a stripped down NEC2 engine. 4NEC2 and
EZNEC use the full NEC2 engine from Lawrence Livermore Labs. I'm not
sure what you're building but allow me to offer a clue. I recently
threw together a model of a truly ugly tower with about 8000 segments
including about 2000 pattern lines for various grids and reflectors.
After about 14 hours running, my PIII/933MHz finally spewed out a
result (that told me that I goofed and had to make corrections). I
dragged home a P4/2.8GHz with hyperthreading, which took about 8 hours
to run. This was getting ridiculous, so I dragged the program and
model to a customers office, and ran it overnight on his P4 2.8GHz
dual core, 4GB RAM, 1333MHz FSB, SATA2 drive, etc. It doesn't get
much better. It ran in 3 hours.

The optimizer isn't much better. It will automagically tweak
dimensions to meet a pre-defined set of criteria. If you set the
final criteria too close to perfection, you may get an answer after
the next ice age.

Anyway, I suggest you use a machine with lots of horsepower and start
with EZNEC, 4NEC2, NEC-WIN, MMANA-GAL, or other modeling program using
some of the sample files included with each program. Once you have
figured out how to manipulate and modify those, you can step up to
more complexicated models (such has the giant mess I stupidly created
by throwing every piece of metal on the tower into the model).

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Jeff Liebermann
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