"David Eduardo" wrote in message
...

"John Rethorst" wrote in message
...
In article ,
pamthis (Sid Schweiger) wrote:

Radio-locator.com's maps are
clearly labeled "This image is intended solely for entertainment
purposes,"

Radio-Locator's Coverage Maps FAQ
(http://www.radio-locator.com/cgi-bin/page?p=maps) says:

"To a large degree, AM radio signals travel through the ground"

which I find pretty entertaining.

Why? Groundwave coverage is the principal means of AM station listening.

Although (at the risk that I'll trigger another lesson by Mr Fry about antenna
theory) even the term "groundwave" is misleading. Groundwave propagation is due to
the refraction of the wavefront by the earth....this is one of the reasons why lower
frequencies have a longer groundwave pattern, and why, in the extreme low frequency
band, it goes clear around the earth. The effect is also evident at VHF and higher
frequencies, like the 950MHz STL band. Objects presented to the wavefront (like
mountain ridges) which are similar in size to the wavelength will bend the wavefront,
which results in the limited ability to design an STL path which is (slightly) over
the horizon. It's called "razor's edge" propagation then.
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