Re: NEC-LIST: Large Model Problems....

Rob,
Just from calculating the ratio of a quarterwave 2.4GHz
dipoles (2-180 degree wires) with a 10 foot dish (3.4 meters)
the ratio suggests over 11,000:1. NEC usually needs not less
then 10:1 length vs wavelength to be somewhat accurate. This
is one major problem with modeling microwave frequencies with
NEC on larger structures. For situations like this, I would
using something like TLM, which instead of N^2 matrix's it's
more like N computations. I seen some good results with using
this on X-Band radar EMI - modeling RAM and Navy Mast
structures. Amazing results with larger structures and
microwave frequencies.
v/r

Kenneth Carrigan
Electromagnetic Engineer,
Anteon, Systems Engineering Group
1100NJ Ave, Washington, DC

>>-----Original Message-----
>>From: D. B. Miron [mailto:dbmiron_at_paulbunyan.net]
>>Sent: Thursday, February 19, 2004 8:40 AM
>>To: nec-list_at_gweep.ca
>>Subject: Re: NEC-LIST: Large Model Problems....
>>
>>
>>Good day Rob,
>>
>>Without seeing either the wire list or the source code used
>>to generate it, I can't help you. There are just too many
>>ways to mess up.
>>
>>Doug Miron
>>
>>"Rob Frohne" <frohro_at_wwc.edu> writes:
>>
>>Hi All,
>>
>>I have a student who is trying to model a 10 foot parabolic
>>dish at 2.4
>>GHz. He has around 11,000 segments, though using symmetry,
>>he has
>>reduced the matrix dimensions by a factor of four. He is
>>getting gains
>>that are -999.99 for every direction. The electric fields
>>are not all
>>the same, and may make sense. I didn't get a chance to see
>>that.
>>
>>Does anyone have any advice for my student?
>>
>>Thanks,
>>
>>Rob
>>--
>>Rob Frohne, Ph.D., P.E.
>>E.F. Cross School of Engineering
>>Walla Walla College
>>http://www.wwc.edu/~frohro/
>>
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>>The NEC-List mailing list <nec-list_at_gweep.ca>
>>http://www.gweep.ca/mailman/listinfo.cgi/nec-list
>>
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>>
>

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