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John Smith · January 10th 08, 02:58 AM posted to rec.radio.amateur.antenna

Roy Lewallen wrote:
wrote:
On Jan 9, 11:03 am, Michael Coslo wrote:
AI4QJwrote:
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.
Oh darnit! Here I went and built several antennas designed
with Eznec,
and they have worked just like the program said they would.

I guess I'll have to take the remaining ones down, since I
was only
supposed to discuss them, not actually make and use them. Thanks for the
correction!

- 73 de Mike N3LI -

But you may have a problem discussing on the ng exactly "why" they
work. Why would you want to discuss an antenna if you don't care "how"
it works, you only care "that" it works? There are some people that
operate at 27MHz who don't care how their radios work, only that they
can peg your meter at 10 pounds.

A whole lot of people have gained a better understanding of why antennas
work by using computer modeling. They observe how they work, discover
it's not how they thought they worked, and are prodded into learning why
they work. I've learned a great deal myself this way, and many
conversations with EZNEC users over the years shows this to be a common
benefit from modeling. It allows you to immediately see if your concepts
are sound by showing you the results of their application. NEC and EZNEC
don't design antennas; they only tell you how the antenna you've
designed works. Chances are you won't design a very effective antenna if
you have no idea why they work. People truly interested in learning more
about why antennas work will arm themselves with as many available tools
as possible.

A recent example of this philosophy was the transmission line analysis I
recently posted. After working through all the math, which came from a
basic understanding of transmission line analysis, I simulated the line
with SPICE to confirm that my analysis was correct. Had it shown
something different, I would have gone back to the math, or the model,
or my basic view of transmission line operation, to resolve the
discrepancy.

Arguments against using computer programs for antenna analysis are about
the same as those against using a calculator to perform arithmetic. No,
on second thought, more like arguing against using a computer to solve
systems of differential equations.

But, each to his own.

Roy Lewallen, W7EL

Computer modeling is wonderful ...

Constant examination and keeping it up-to-date will allow it to hold
this status ... it is hardly in a finished form ...

Regards,
JS