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Re: Topband: More anecdotal "stories" to cause one to stop and....

To: <topband@contesting.com>
Subject: Re: Topband: More anecdotal "stories" to cause one to stop and....
From: "Richard Fry" <rfry@adams.net>
Reply-to: Richard Fry <rfry@adams.net>
Date: Fri, 13 Sep 2013 06:43:47 -0500
List-post: <topband@contesting.com">mailto:topband@contesting.com>
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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