Topband: K0SR calculation

[Nm7m at aol.com]

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     In response to my recent posting on 3B9C propagation, K0SR in
St. Paul, MN replied, outlining his experience: regularly hearing
weak 3B9C signals around 0100 UTC but unable to make contact.  In
an effort to understand his problem, another set of PropLab Pro
calculations were undertaken for his path (16,400 km at 327.5 E
azimuth).

     That path crosses the lower part of the auroral zone, making
signal receptiion at K0SR subject to auroral absorption and also
equatorward skewing.  But the PropLab Pro calculation still shows
ducting, now starting at 5,500 km from 3B9C, over the Gulf of
Suez.  That location is about 2,000 km beyond the site proposed by
the 3B9C operators for an ionospheric tilt, sending signals toward
North America.  That tilt could arise from thermal effects because
of the proximity of the terminator but would not provide the sort
of sudden "ionospheric gate" proposed to fit their experience.