On 8 Jan, 19:01, Roy Lewallen wrote:
AI4QJ wrote:

The NEC program is just a computer model, for discussion purposes only. I
think there are far too many variables in real life for the program to take
into account. It may be valuable but I am not yet convinced it is
infallible. . .

Exactly the same can be said of any of the other models we successfully
use daily. "Resistances", "impedances", "capacitances", and other
objects we routinely use in circuit analysis, are "just" models of real
objects. Likewise, the equations we use for solving all kinds of
problems, including transmission line and circuit analysis problems, are
"just" models of actual behavior. Ohm's law is "just" a model of the
relationship among V, I, and Z. The fundamental equations relating
currents and fields, Maxwell's equations, and all other equations used
in engineering are "just" models of real behavior.

*All* models are subject to intelligent use. A person modeling a real
resistor as a pure resistance at 50 GHz will get just as bad results as
a person modeling a dipole on a circuit board in a smart key in a pocket
as a free-space dipole. No model, not even a simple resistance, is
infallible -- even it can be misused by someone not having the
underlying knowledge necessary to apply it. So of course computer models
aren't infallible either.

But there are many, many real life antennas which can be modeled with
great accuracy with NEC. I use EZNEC regularly myself in my consulting
work to design antennas, and find very good correlation with anechoic
chamber pattern tests, network analyzer impedance tests, and performance
results. So do the many aerospace companies, military organizations,
space agencies, universities, research labs, domestic and international
broadcasters, and many other companies that use EZNEC daily to help
design real antennas that work as predicted. But those aren't the only
people successfully modeling with EZNEC -- a large number of amateurs
successfully use it also.

I'm not sure what it is that makes models inherently less accurate or
believable if the equations are solved with a computer than if they're
solved by some other method. Perhaps you could explain.

Roy Lewallen, W7EL

Answer why Maxwells laws must have a proviso added when they are
considered LAWS
nOT theory but law When you jump the traffic lights you have broken
the law.
Maybe your exception has a good reason but by its very use you have
invalidated the laws that you are seeking to abide by.This does not
mean that the program does not reproduce actual antennas because
numourous modifications to make sure that it does. Doing this is
tantamount to saying that Maxwells laws need the help of experts such
as your self. Seems like a good job is being done but it doesn't
change the facts. You have taken the lead offered by Maxwell but have
reserved the right to modify these laws to obtain a better computor
model.
Why was this deviation added when the discharge of a capacitor is in
no way sino-soidal?
Same goes for a inductor. Explain your deviation from the laws of
Maxwell!
As a computor programmer you never gave credence to other antenna
programs that produced tipped radiators for maximum gain for the
polararisation required? You stayed quiet to protect the sales of your
own program and thus by your silence allowed true facts to be
distorted on this newsgroup. There were many opportunities for you to
say that Eznec confirmed this finding
but you said nothing, which in itself is a insult to ham radio. You
modified Maxwell's laws and that is prohibited in mathematics if one
is to follow a mathematical law which you then invalidate.
Nothing personal intended, just a statement of facts as I see them. I
will accept factual changes if you deign to point them out in detail
so they can be confirmed or denied.
Art