Topband: skew path example

[Dan Robbins]

During the last solar cycle minimum, both NL7Z and I worked Bernie,
ZS4TX on 160.  NL7Z (Kevin) worked Bernie around ZS sunset.  At that
time Kevin was hearing other stations over the pole from Europe and was
using an antenna that was best in the northerly direction.  From all
indications this was a true short path QSO, due North over the pole,
through EU and AF.

My QSO with Bernie was around ZS sunrise a day or two later.  At that
time, I was hearing no EU nor any stations over the pole so short path
seemed unlikely.  I was hearing W3 and W4 at that time and Bernie was
only audible on an antenna which works best to the East.  LP was not
possible as the South Pole was bathed in sunlight.  From all
indications, Bernie's sig was coming somewhere from 90-120 degrees.  I
heard Bernie several times on this same path, but signals were always
weak and he only heard me once.  While the propagation mechanism is
unknown, I'm sure glad it was there!

Up here close to the auroral oval, it is not uncommon to see high angle
radiators work best at times on 160.  The reason appears to be
absorption in the auroral induced E layer:  a high angle signal passes
through the E layer much quicker than a low angle signal.  There's a lot
less absorption in the quicker passage.  Since SE Asia is one of the
best areas for sporadic E in the world, maybe a similar mechanism
affected the XZ work.


                                                                Dan KL7Y