Re: Negative resistance

I have also noticed this problem of negative input resistance. However,
when I converted NEC4 to run on Linux the problem was not as bad as it was
on a Sun station. NEC4 also runs almost as fast and the computers are a
lot cheaper. (ie a 486-DX100 seemed to be only 1/2 the speed of a
Sparc-20) If enough people are intrested in how I converted the code I
will make a web site with the description of my efforts. I think the
difference is in how the the compiler/Kernel handels the math. I guess
linux just carries more decimal places.

I have also noticed in some of my models, if I make the element sizes
larger wrt to the wavelenght I can get a positive resistance. I just feel
better when I see a positive real resistance on electrical small antennas.

(The funny thing was our sloppy calibration of a HP8753 also reported
negative resistances at the same places!)

Adam

On Mon, 29 Jul 1996 FHRaab_at_aol.com wrote:

> This regards the question from LGOLDSTE_at_mailb.harris.com about negative
> resistance in NEC output. We have observed this many times when working
> with short antennas whose input impedances are high. The angle of the
> impedance vector is close to zero and NEC apparently rounds the
> resistive component to a small negative number. We never did come up
> with a good solution.
>
> Frederick H. Raab, Ph.D.
> GREEN MOUNTAIN RADIO RESEARCH COMPANY
>
>

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Received on Tue Jul 30 1996 - 14:34:00 EDT