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Old August 22nd 06, 01:55 AM posted to rec.radio.amateur.antenna
lu6etj lu6etj is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 143
Default Vertical radiation from horizontal dipole?

Dear Roy:

Stupendous explanation, I also think, as Denny, that should be included
in the antenna book to highlight this aspect, because a lot of friends
tends to believe that the horizontal dipole only emits with horizontal
polarization...

In fact, my question arose when comparing the relative difference
between the vertical field and the horizontal one in the free space and
on the proximities of the real ground (or with the perfect ground also)
and to notice a bigger intensity of the vertical field near to the
ground (relative to the horizontal one), taking reference with the same
relationship in the free space.

My hypothesis was that this would be due to an asymmetric distribution
of the displacement currents taken place by the presence of the graund
that would cancel part of the vertical field in low angles.

I was looking for the correct explanation of such an asymmetry. Now I
think that your explanation, based on difference in the reflection
coefficient, seems to be more appropriate.

It put my accent in "the low height", because I was in a friend's shack
that uses EZNEC 3 (I am more familiarized with MMANA which I use
because it is free and not because I prefers it to yours, that is very
good) and I am got confused with automatic way of locating the outer
ring, suggesting me a great intensity of vertical field (reason why the
results they were too optimistic). It was my fault because the text on
the results gives the outer ring value (but one so many times doesn't
read the tiny letters...).

When, at your suggestion, download EZNEC 4 Demo, I realized (when
opening Desc Options) that the 0 dB corresponded to an external ring of
approximately -10 dB or less, (maybe it would be good a "warning" to
avoid troubles at peoples as fool as me ;) )

Those first results took me to think that the vertical field could have
more relevance on comunnications at short distance by terrestrial waves
(very low angles) on the lowest bands...

Anyway, maybe the most interesting thing that has arisen of this
question is to remember us that the horizontal dipole Ądoesn't sends
only polarized horizontally waves..!

Thank very you for your quick answer and my congratulations for your
great program.

Miguel Ghezzi (LU 6ETJ)
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