Jack WS3N wrote:
Then it would seem that what you call the surface wave must be the
remaining part of the complete solution, and so it must decay exponentially
in the vertical direction. ... a decaying solution can't be projected in a
straight line and assumed to reach the ionosphere.
The radiated field of a vertical monopole present on the surface of lossy
earth decays at greater than a 1/R rate. But, for example, the field shown
at a horizontal distance of 0.1 km in my surface wave plot for an elevation
angle of 5 degrees is not located on the surface of the earth. It is about
9 meters above it, and in fact, is a space wave.
Space waves DO decay at a 1/R (non-exponential) rate until they reach the
ionosphere.
Here is a link to a clip from Radio Engineers' Handbook by F.E. Terman (1st
Edition), showing that the greatest single-hop range for radiation from a
1/4-wave monopole leaves the monopole at elevation angles below 5 degrees.
The reduction in skywave field intensity seen in this clip beyond 150 miles
downrange is due to the 1/R losses of those longer paths.
http://s20.postimg.org/g3yy1uust/Terman_Fig55.jpg
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Topband Reflector
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