Pete,
I've been watching some of the replies on modeling etc. Perhaps there is
some confusion over what antenna modeling software is doing and how it is
done. I'll try to put it all in perspective. Let's not put the cart before
the horse.
Antenna modeling comes first and it is all mathematical based on long
standing antenna theory. The equations have been around for some time (way
beyond my comprehension!). Before the availability of computers,
calculations were done by land. This was a very long, slow and labor
intensive job!
This being said, what the authors of antenna modeling programs do is first
write programs to solve the mathematical equations mentioned above. This
does not mean compiling "look up tables" (although there may be some
imbedded in the program) based on know measurements.
Then, using the generated computer modeling programs, many theoretical
antenna patterns are calculated for a variety of antenna types used in
different physical configurations (free space, height above ground,
standard ground types etc.).
Next, the antennas modeled above are accurately built and tested by someone
with adequate measurement equipment on an antenna range or in an anachoic
(?) chamber.
Finally, the measured results are compared to the theoretical (modeled)
results to asses the accuracy of the programs. Only after numerous
measurements and comparisons are the modeling programs certified to be
accurate and made available to the public.
Over the years since antenna modeling has become available (most notably
with the Morris programs in the mid 1960's at Harvard), programs have been
updated, improved (especially for the customer interface...NEC4 supposedly
being the worst to use) and more functions made available. An example is
the complex ground simulations that, although supposedly very accurate in
NEC-4, are still being challenged!
I hope this clears up some of the questions and misconceptions I
occasionally see on this reflector.
73,
Joe, W1JR
At 10:55 AM 2/2/2002 -0500, Pete Smith wrote:
>At 10:28 AM 2/2/02 EST, RLVZ@aol.com wrote:
>...
> >IF SO, WHAT HEIGHTS WERE THE RECEIVE ANTENNAS AT? LOTS AND LOTS OF
>VARIABLES
> >HERE... SO HOW ACCURATE IS EZNEC?
>
>EZNEC uses the NEC-2 engine, which was developed for the US Government, at
>great expense, and is the best thing currently available short of NEC-4,
>which is very expensive to end users, even today.
>
>I think there is a general consensus that its results are reliable (except
>for those known cases where they are not).
>
>
>73, Pete N4ZR
>
>Sometimes a tower is
>just a tower
>
>
>
>
>
>________________________________________________________________________
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>Order online at http://store.eham.net.
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________________________________________________________________________
Where do you get ICE bandpass filters & beverage matching boxes? The
same place that pays for the hosting of this list: The eHam Store.
Order online at http://store.eham.net.
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