The elevation patterns of vertical monopoles over real earth has been
discussed in recent threads here
(http://lists.contesting.com/archives//html/Topband/2012-10/msg00140.html).
The common belief based on NEC far-field elevation patterns for those
conditions shows little relative field at low vertical angles, and zero
field in the horizontal plane. However the surface wave must be included in
a complete analysis of monopole performance, because it contributes
substantial low-angle radiation that will reach the ionosphere to generate
skywave service under the right conditions.
Below on this topic is part of an e-mail exchange of a few months ago
between Gerald Burke of Lawrence-Livermore National Laboratory and me, and
is quoted with his written permission. As many will recognize, Mr. Burke is
co-author of the software engines used in NEC computer programs.
This text applies to NEC surface wave plots attached to my e-mail to him.
Hello Mr. Burke -
Would you expect the fields at elevation angles of 1 to 10 degrees
in these plots to continue on to the ionosphere, and under the right
conditions be reflected back to the earth as skywaves?
R. Fry
The low angle 1/R fields should reach the ionosphere, although perhaps not
accurately predicted by NEC, since it does not include the effects of earth
curvature and the ionosphere.
Regards,
Jerry Burke
LLNL
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