With due respect to Jim, Rick, David, Roger, and others who have waded in
on this topic...some of which is captured, below....might I offer a
simplistic observation on what is a complicated topic?
The physics of the near field environment will act the same, for arrival or
departure of signals. What is different is, the signal ARRIVAL angle and
phasing, is determined by the ionosphere, not the antenna. Therefore, how
the refractive behavior of earth relates to the arrival of that
complex...and different...signal is anybody's guess.
The ANTENNA, however, will still have a response pattern determined by the
geometry and refractive content of the immediate environment. Whether the
ionosphere presents signal inside that pattern...with what polarization or
phasing, that's another matter.
As Jim Lux, observed, below..."as long as there is no nonlinearity in the
system"... The ionosphere makes the optical ray-tracing analogy
inapplicable, in its simplicity. Not wrong..just not sufficient.
His comments concerning polarization are correct, and impact the problem
significantly. The suite of optical rays are now a swarm, with varying
polarization, going through what MAY be a polarized filter (earth). At
best, the result is a blur.
So, yes...you can assume reciprocity. You might be right,
you might be wrong. It doesn't matter, either way.
Just put the damned antenna up and get on the air!
WHY did we have interesting 10m openings during CQWWSSB, with zero sunspots?
N2EA
Rick wrote:
>>
>> It seems to me that a good portion of Station B's signal arriving at the
>> hill could overshoot Station A because it wasn't diffracted enough. The
>> path taken by the signal from B to A would be identical to the path
>> taken by the signal from A to B EXCEPT for the portion between Station A
>> and the hill. Think directional coupler.
>>
Jim Lux responded:
Uhh, nope.. even though it sort of seems that way at first glance..
Imagine that the top of the hill is a big lens or prism that bends the
ray (which is what diffraction is, in one sense)..
Launch a ray from A towards B and it follows a certain path, apparently
bending over the top of the ridge. Some distance after the hill, stop
the ray and send it back exactly as it came. When it gets to the
prism/lens it will bend it just like it did on the outbound trip and
wind up at A.
As long as there no nonlinearity in the system, it works.
Where there IS non-reciprocal propagation you need something else. here
are some examples:
a) propagation through the ionosphere, which is anisotropic.
<snip>
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