Satgen583  Electronic Doldrums by GM4IHJ  (BID SGEN583)  2000-05-27

According to Shakespeare. Winter is the time of our discontent. To be
followed by glorious summer. However , as radio amateurs, we see the
situation phase reversed. Winter DX glorious, Summer discontent.

With Summer 2000 now upon us . Amateur radio seems temporarily
becalmed, in what sailors used to call the doldrums or horse
latitudes - places where nothing much happens. HF sat DX disappears
and we wait anxiously for Phase 3D. Of which, given a successful
launch and setting to work period , we cannot expect general access
until autumn hopefully brings in a winter of great content.
A winter which at IHJ will be taken up by feverish building and
assembling of equipment and antennas ready to operate all the new
bands this satellite will provide. Noting that no such preparation
has as yet taken place. IHJ being a thorough pessimist . A state of
mind conditioned by the preparation of a super antenna outfit for
Phase 3A , followed by a high class but low powered mode L station
ready for Phase 3B. Both of which disappointed when 3A splashed down
instead of orbiting and mode L 3B required so much power to access, a
total rebuild of the equipment would have been necessary before any
operating could have occured.

So not counting chickens before the eggs hatch. Work on Phase 3D
equipment will start at IHJ only when Phase 3D is operational.
Meanwhile with RS13 Sub horizon DX having entered its summer doldrums
phase, the magic propagation whereby the satellites beacon delineated
the various bands of ionospheric anomalies both north and south of
the equator has all but disappeared, and will not be back until
September. This despite a super rise in solar flux which came just
too late to catch the last of the winter seasons great DX.   A
situation which seems to have surprised some correspondents. Although
it has been a feature of HF radio operating, well described in
amateur radio journals, for at least 40 years.

Which length of time may account for some folks being unacquainted
with these sad facts. So please excuse me if you have heard it all
before . Here is the gist of the somewhat counter intuitive behaviour
of the ionosphere at the winter/summer change over. 

In winter the solar illumination angle on your hemisphere, is low.
But ionisation is concentrated in a single F layer , and if solar
flux is high, critical frequencies are high , and excellent HF
propagation results. But when summer comes along. The solar
illumination angle is greatly increased and one might be excused for
expecting greater ionisation = even better DX. Unfortunately however
this is not quite the case. There is greater ionisation, but the F
layer splits in two and, part of it expands much higher in altitude.
With the overall effect that the now greatly extended ionosphere is
locally less dense than before , Thereby producing lower critical
frequencies = summer doldrums = a marked reduction in terrestrial and
satellite HF DX possibilities.