Topband: 160 Meter Propagation

[Robert Brown]

Tom,

You say that "signals will ALWAYS seek the path of least resistance and
absorption."  I hate to say it but I do not recognize that as a principle
that follows from Maxwell's Equations, as applied to propagation.  Maybe
you can amplify on your remark.

In addition, you remark that we are "moving into the dreaded winter
higher absorption anomaly, which in a sense is weather related."  

I would suggest that you check further on the winter anomaly; it was
discussed by Appleton and Piggott back in 1954 and is a DAYTIME
phenomena, not when 160 meter DXing is done.  The modern interpretation is
that it results from an increase in the nitric oxide (NO) content of the
atmosphere due to auroral bombardment and winter storage in the dark, 
polar vortex.  With meridional circulation, some of the NO leaks out at
lower latitudes and is ionized by sunlight.  Ergo, greater absorption in
daytime hours.

I think the key to this entire discussion is found in looking at the
normal ionospheric processes that take place.  It is not enough to infer a
path direction from an antenna orientation; one must follow signals in
those directions but recognize that they are subject to normal refraction
and absorption in the ionosphere that is encountered.  In short, all this
is normal radio physics as long as we do not leave out vital parts of
the process.

73,

Bob, NM7M


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