RE: NEC-LIST:NEC 4.1 & g77

Hi John, et al,
Using two different NEC v2 programs I get the below answers running your
nec file on a Win NT machine:

97.335 + j7.697 with a gain of 6.14dBi.

Which is the experimentally validated result? And is a +/- 10% good
enough for modeling. NEC 4 I hear has some flaws in the way it treats
some objects, NEC 2 has some shortfalls as well. Both should be able
to predict the impedance of this simple cone at 3MHz.

v/r
Ken Carrigan

-----Original Message-----
From: John B. Wood [mailto:wood_at_itd.nrl.navy.mil]
Sent: Tuesday, July 09, 2002 8:31 AM
To: nec-list_at_gweep.ca
Subject: Re: NEC-LIST:NEC 4.1 & g77

Hello, all. After comparing the results of several simple antenna
models run on a Linux platform with the same models run on Windows
and HP-UX platforms I was ready to believe g77 was compiling NEC 4.1
into a reliable executable, Recently I tried the simple cone model:

CE cone - test - 3 MHz
GW 101 16 0 0 3 70.71 0 73.71 .012
GW 151 16 70.71 0 73.71 0 0 73.71 .012
GR 1 10
GW 1 2 0 0 0 0 0 3 .012
GE 1
GN 1
EX 0 1 1 0 100
LD 5 0 0 0 5.7E7
FR 0 0 0 0 3
RP 0 5 2 1001 90 0 -10 45
EN

I obtained the following driving point impedances (rounded to 3
significant figures) and maximum gains using this model:

Platform/Compiler Impedance Max Gain

Red Hat 7.1/g77 113 - j849 ohms +8,27 dBi

Win98/Compaq Visual Fortran 6.6 110 + j1.39 ohms +5.61 dBi

HP-UX 9.05/HP Fortran 110 + j1.39 ohms +5.61 dBi

As can be seen the reactive part of the feedpoint impedance using the
g77 compiler differs considerably from that obtained with the other
platforms. Again, scratching my head and wondering what's going on
here. Your comments are very much desired. Sincerely,

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