RE: backscatter
> Earl has the only explanation that makes any sense to me. The direct path
> is not open, the path to a skip point that will produce suitable
backscatter
> is open, so what you hear is the backscatter from that point, which would
> likely be way off beam from the normal direction.
Sorry to drag this out but the "signals of" VK3ZL and others on paths far
from poles skew and move, all with a path nowhere near the auroral zones. It
is an almost daily occurrence, just like we can have a strong sunset peak
that fades away or any one of a infinite number of patterns. SW as his
daylight fades, maybe NW maybe not, and then who knows where or what at my
sunrise.
It also rarely sounds like backscatter. Anyone who has listened to
backscatter knows the soft mushy sound of backscatter caused by the wildly
varying long group delays in the transmitted data. These are clean hard
signals, unless you copy the vector sum of multiple paths at once with a
broad antenna.
Today was a wonderful skew of 3ZL, and the strongest peak was in a ragchew
while Bob watched the view around him go from daylight to dark. The ZL
digi's faded from S-9 down to S-2....never to have a second wind. VK3ZL
squeaked in SW after it was light enough to read a paper, 20dB weaker than
his sunset peak.
We won't pin any of this down to something as simple as a backscatter
reflection from terrain or reflections from auroral regions. Far too many of
us know better than to let that pass. It is somewhat common to perhaps
typical to watch a signal path shift in moments, let alone hours.
Tracing propagation, skewing, and peaks back to one, two, or even three root
causes with clear boundaries and mechanisms is like trying to write software
to run spell check on a bowl of Alphabet soup.
73 Tom
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