Satgen 405  RS12KT Easy Sat Pt3  by GM4IHJ  (BID SGEN405)   28 Dec 96

Recent instances of satellite signals propagating sub horizon more
than 8000 kms, suggest that a review of the mechanisms involved may be
appropriate. Typical examples are :-
SPORADIC E - RS12KT has been regularly putting a signal into Scotland
when it has been far to the south overhead latitude 9N . This seems to
be a simple horizon extension of about 9 degrees of latitude
consistent with propagation via the E layer somewhere over north west
Africa.
F LAYER - Japanese signals repeated by RS12 are being heard in New
Zealand when RS12 is above the New Zealand horizon, some 8000kms or so
from Japan. Signals from 7Q in Southern Africa are getting into RS12
when the satellite is over Greenland, and just above the horizon in
Britain. Clearly neither low altitude (100 km) Sporadic E , nor single
hop F layer refraction can account for this latter incident. Indeed
these Southern Africa incidents are not new. They were first noticed
via Soviet Cosmos 1686 transmissions back in 1986 , ie in roughly the
same solar conditions as at present = bottom of the solar activity
cycle.
SUB POLAR - Propagation involving both RS12 and RS10 satellites over
Alaska, being heard in Britain , antennas pointing eastwards, implying
propagation over sub polar paths out to 7000 kms. Unfortunately how
ever the locations at either end of this pass never experience
concurrent "socially acceptable daytime hours". In some cases the
satellites can be heard shortly after leaving the G footprint and
thence eastwards and onwards all the way to overhead KL.
These Arctic events seem to accompany polar propagation enhancement
events which can also open terrestrial 10m to W from G, albeit
briefly. In addition it is often possible in these conditions to hear
satellite 29 Mhz signals when the satellite is over the other side of
the North Pole, unfortunately an area possessed of more polar bears
and seals , than amateur satellite operators.
ANTIPODEAL - In addition to the above north polar events, it is
noteworthy that brief 2 to 6 minute bursts of RS12 and RS10 beacon
telemetry are regularly reported  from satellites near the South pole
. The area to the west of the point antipodeal to Britain is the most
frequent source of these signals. No UK contacts have ever been
reported from east of the UK antipodes.
It is appreciated that the above hardly provides a clear guide as to
when to expect these events. But the Sporadic E to the south over
Africa appears to be present all year round ie it is not seasonal, as
the northern European or North American local sporadic E is. While the
polar and sub polar events consequent on activity much higher, up in
the F layer of the ionosphere, do seem to follow some. but not all
solar mass expulsion events. There is however no clear pattern as yet
associated with the long range events coming into the UK from the
South Atlantic , Southern Africa and the UK antipodes.
In fact the best guide is constant monitoring of the satellite beacon
frequencies, followed by a quick shift to the communications
frequencies if anything is heard. Indeed anywhere in the world is in
range , particularly via RS12KT, as G3IOR demonstrated a few years
back , with his successful satellite qso to ZL New Zealand. But luck
of that sort comes only to those who prepare and practise for it.