At 02:45 PM 11/3/2007, David Gilbert wrote:
>Yes, I've been thinking about all of this in terms of wave theory,
>which I'm pretty sure is valid for HF ;)
YUp, it sure is valid. :-)
Physical (wave) formalism is completely accurate everywhere but tends
to be computationally very tedious when thew wavelength is small
compared to the physical scale of the problem.
Geometric optics gives the asymptotic solution to the wave optical
problem in the high frequency/short wavelength limit and is easy to compute.
>My basic hypothesis is still the same, though, at least until
>someone can help me wrap by mind around an explanation of my error,
>that an HF signal (a wave of energy) could react differently to an
>asymmetric terrain feature when traveling from opposite directions
>along the exact same path as long as the asymmetry was significant
>relative to a wavelength.
Dave, there is no error in your thinking. The only confusion is about
exactly what "react differently" means.
Suppose I send a plane wave at some complicated diffractive surface.
Let's say this plane wave was initially moving from left-to-right in
one direction with a uniform amplitude. Upon encountering the
surface, the wave gets diffracted and ends up going off to the right
in a bunch of different directions with differing amplitudes and phases.
What reciprocity says is if I send in a bunch of waves from the right
from different directions with differing amplitudes and phases such
that they replicate the output seen above, I'll get a copy of the
original wave moving to the left.
73,
Mike K1MK
Michael Keane K1MK
k1mk@alum.mit.edu
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