Friends in Radio Land -
While Tom, KN4LF, says that the simplest way to look at skewing or
refraction is by means of a "principle of least absorption" , I
still maintain that principle does not exist in propagation theory.
Let me prove it to you.
As you know, the advance of electromagnetic waves is governed by
the Maxwell's Equations. In simplest terms, that means there is
a connection between the distance advanced dS and the change in
direction d0 of the wave. That "connection" is called Snell's Law
and should be familiar to anyone who has taken an elementary
course in physics. By using Snell's Law, it is possible to trace
out, step by step, the paths of waves that are launched from an
antenna.
Another part of electromagnetic theory concerns how the intensity
of a wave changes as it advances through the ionosphere. In the
simplest terms, theory indicates the change in intensity dI as
the wave advances a distance dS depends only on the electron
density Ne encountered and the rate of collisions fc of electrons
with neutral constituents.
The important thing to note is that the change in intensity does
NOT involve the change in direction of a path. In mathematical
terms, that means it is NOT possible to define a valid wave path,
in distance and angular variables, by intensity considerations
alone. In short, a path must be worked out first using refraction
by Snell's Law before calculating signal strength variations, not
the other way around. QED.
While Tom, KN4LF, argues that his discussion for ham audiences is
in keeping with the idea of KISS ("Keep it simple, Stupid"), I am
not willing to do that at the expense of scientific rigor. That's
where we differ.
73,
Bob, NM7M
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