Topband: Skewed paths

[Robert Brown]

Friends in Radio Land-
 
While it was not my intention, my remarks about a polar path in a
time of weak auroral activity seems to have triggered a discussion
about skewed paths.
 
Let me be clear on this: I am not opposed to the idea of skewed
paths; it is just that I would like to understand their origin.
After all, as I indicated in my response to Tom, W8JI, there are
only three ways that signals are propagated through an ionosphere:
refraction by ionization gradients, scattering of signals by
ionospheric or atmospheric irregularities as well as irregular
surfaces (ground or water) and reflection by auroral ionization.
 
Any report of a skewed path should be able to be analyzed in those
terms.  It is my view that reporting skewed paths should give a
complete geophysical description of the event - date, time,
frequency, geomgnetic and ionospheric conditions - so that such an
analysis can be made.
 
If the direction of arrival of skewed signals does not change in
the course of time, by days or months or years, that says one
thing.  For example, it could be the result of an orographic
effect propagated upward into the ionosphere over a high volcano.
In support of orographic effects, the Russians and Chinese have
identified ozone effects over various mountain ranges like the
Himalayas and Andes by using data from NASA satellites.  For my
part, I have found radio effects on VLF signals which can be
attributed to orographic effects from the Rocky Mountains.
 
But if the arrival of skewed signals changes in the course of a
morning, that tells me it is the result of a solar effect, say
absorption changing a path as the sun rises.  Like Ford, N0FP, I
consider that type of an effect to result from back scattering
of short-path signals and have discussed it at some length in the
Nov/Dec 2000 issue of QEX.  And a more elementary discussion is
found in the Nov/Dec 2000 issue of The DX Magazine.
 
In closing, let me say that there are some among the Top Band
community who are interested in propagation.  We cannot be on all
paths at all times and thus rely on others to report conditions,
particularly anything seeming unusual.  Of particular importance
to us would be complete reporting of date, time, terminii, as well
as geophysical conditions.  But that is not enough as we would
hope that operators would be sensitive to the various means of
signal propagation and indicate their ideas of where and how
skewing originates.  That would serve to advance Amateur Radio.
 
73,
 
Bob, NM7M