Satgen149   RS12 DX BONANZA              by GM4IHJ              3rd Feb 92

G3IOR and others , have been reporting the long range DX potential of
satellites like RS12 mode K , ( 21 MHz up, 29 MHz down ), for years. I for
one had given up expecting people to take note, even when, as recently 3
Gs were in QSO together whilst RS12 was over western Alaska. It was long
after KL bedtime (UK AOSs 1155+1334ut 31Dec) but many of the stations on
the route eastwards from UK to KL could have joined in if they had tried.
    Last week , this all changed, and it did so on what is perhaps the
most curious of RS12s propagation modes. At 2142 ut on 24th Jan 92 , RS12
was accessed by G3IOR on a normal above the horizon pass, coming from
North to South passing about 1000 kms to the east of Norwich England. As
G3IOR tuned around he got a QSO with W1PK in the Eastern United States.
    At that time the satellite was over Central Europe well to the east of
UK. So how did W1PK roughly 7000 kms west of RS12, manage to access it ?
The ionosphere over UK was typically thin long after sunset = Low maximum
usable frequency = transparent to G3IORs up link and down link. But no 21
or 29 MHz ionospheric link existed between G3IOR and W1PK. The typical
daylight ionosphere providing high MUF did however still exist over
Newfoundland , and though W1PK could see this ionosphere, it did not allow
him to get into UK. BUT it did allow him to chordal hop right over UK high
above G3IOR to the RS satellite 1000 kms above Central Europe. So W1PK had
two way contact with the satellite and so did G3IOR, hence the QSO which
took place.
      As Pat G3IOR has pointed out , there is a psychological difficulty
in appreciating that a satellite well to your east can brings you signals
from remote DX from way behind over your left shoulder from a station far
to your west well below the satellites normal horizon. Do not be put off
by this. QSOs with several other USA call areas have already been
achieved. Indeed examination of the W1PK QSO suggests that at the time
RS12 was in range of states far to W1PKs west , in W7, W6 , W0 etc via a
long zone of ionospheric propagation of 21 and 29 MHz signal extending
across the USA.
     Now American stations are getting the message, we can expect more DX,
but because RS12s track around the earth changes its alignment roughly 50
degrees a month, we can expect the sources of DX to change in step with
this gradual change of RAAN Orbit Right Ascension. Even so you may have to
be quick. This favourable active Sun high MUF phase supporting 29 MHz
propagation may not last. It will certainly be less good this next summer,
but it may come back briefly next winter before the Sun starts a rapid
decline to Solar cycle minimum.
     This is a very complex subject. The RSGB Space Radio Handbook
contains a detailed summary of what to expect. If you have it , study the
details in the RS section of the Amateur Radio Satellite chapter pages 90
to 94. Or , if you are not a great reader simply tune any RS12 orbit any
time whether inrange of you or not 29.408 lower beacon to 29.454 MHz upper
beacon/robot , with the easier to read CW occuring just above 29.410 .
Possible DX is - around end Feb early March G ,to sat over JA or Eastern
VK around 0830 ut : G, to sat over Singapore around noon utc : with a very
slight possibilty of contact with ZL around 0500/0600 after the sat has
gone past UK and is up near Nova Zemlaya in the Russian Arctic ie sat very
near LOS to North east of UK. 73 de John GM4IHJ @ GB7SAN