On Sat, 14 Nov 2009 22:23:05 -0800 (PST), Art Unwin
wrote:

Cebic found when comparing different style programs that some behaved
well in certain circumstance where others did not. Yet all antenna
programs
are based on the use of Maxwells equations where all programs should
have the same results, after all Maxwells equations are exact and not
fudged. One of the reasons is that since Maxwells laws are exact
radiators used must be resonant at repeatable points designated as a
period.
Fact is that most users use fractional wavelength designs, usually
a half wavelength, that is not resonant at repeatable points where
the area around the datum line of a sine wave is never equal when
generated around a tank circuit.
The reason for this is "voltage over shoot" which gets smaller
with every cycle but never disappears. Thus when programs are used
based on fractional wavelength radiators the results will never show
100% accountability and in fact efficiencies derived will be in the
order of 92%!
If the radiator is of a wavelength then one is not using a "fudge"
figure
in the calculations and then becomes possible to attain total
accountability with efficiency of 100%. regardles of what type program
is used.
If one is to use exact equations, as are Maxwell equations, then
one must also use measurements that are also exact and repeatable and
that is definitely not fractional wavelengths!
What one gains from this aproach is that any radiator of any shape,
size or elevation can provide figures in the order of 100% as long as
the radiator is a multiple of a wavelength where it is resonant at
exact and repeatable measurements.
If anybody can give pointers that refute the accuracy of the above I
would be very interested in hearing them


How do I simulate a sheet metal or other metal structure in NEC,
when the software only knows (infinitesimally thin) "wires"

w.