Topband: Skywaves from Monopole Surface Waves

[Richard Fry]

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