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Old November 26th 08, 06:19 PM posted to rec.radio.amateur.antenna
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Default Low-angle Elevation Gain of a 1/4-wave Vertical Monopole

Richard Fry wrote:
"Roy Lewallen" wrote
Of course the standard far field analysis doesn't accurately depict the
field close to the antenna -- it's a plot of the field at points very
distant from the antenna, as clearly explained in the manual. NEC allows
you to include the surface wave if you want, and it accurately shows the
total field including the surface wave at a distance of your choice.

_________

Not the versions of NEC used by most amateurs.

Those versions show zero or very low gain in/near the horizontal plane
for a
vertical monopole over real earth. This leads to the common (mis)
belief
that those are the gains of the radiation pattern _originally
generated_
by the monopole.

But that belief is untrue.

RF


I'm not aware of such a widely held misconception, but it is indeed untrue.

You must have conducted some sort of survey to find out what "version"
of NEC-2 is used by most amateurs, you know more than I do about it.
Although there are a few minor variations of NEC-2, there's not enough
difference to justify characterizing them as different "versions". And
every one I've seen has the capability of producing data which include
the surface wave. It's done with a simple entry on the RP "card".

A number of different compilations of NEC-2, every one of which as far
as I know which includes ground wave analysis, can be had at
http://www.si-list.net/swindex.html. You can also get the manual there,
where you can learn about how to get the ground wave data from it.
You're obviously much more interested in ground wave field strengths
than most amateurs, so I suggest that you download one of the free NEC-2
compilations, and the manual, and them for your investigations.
Remember, it's done with the RP "card".

Roy Lewallen, W7EL
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