Satgen 551  HF Propagation RS13  by GM4IHJ   (BID SGEN551)  1999-10-16

As previewed in Satgen 550 , the HF satellite scene has become very
interesting . With Sub Horizon 29.458 MHz signals coming into Scotland
as strongly as anything that was heard in the last two solar cycle
maximums. Results to date cover 3 basic event types.

Broadband (auroral like) signals after LOS to the south
  7th     8th    9th    10th    11th     12th October 1999 times utc
          0900   0931   1000    1027     1054
          1049   1117   1147
  1209    1236   1301
Signal starts coming in whilst clear tone signal is still being heard
3 to 5 minutes prior to LOS, Signal starts doppler high between 300
and 600Hz high and drifts down in frequency to be same as clear tone
at LOS , There after the T2 signal continues for several minutes after
the clear tone has disappeared.

Antarctic Ice cap T2 to T4 signals heard when RS between 65 and 83 S.
   7th    8th    9th    10th     11th    12th October 1999 times utc
   nil           0828            nil
                 1338   1407             1312
          1450   1524                    1647
          1640   1701   1730  
          1818   1847                    1833

North Pacific to Europe continuous tracking from 50N over Pacific
   7th    8th    9th     10th    11th    12th October 1999 times utc
                 0913    nil     nil     nil
                 1047
          1207   1232
   1325   1343   1417
   1510   1537   1603
          1730   1812

As these timings show , there is considerable day to day variability.
Some days are better than others in respect of all 3 event types .
While the gradual longitudinal shift of the RS orbit plane ( circa
west 1.6 degrees/day) is possibly affecting the North Pacific events.

Events occur when RS is under the sun and when it is in darkness.
Indeed when in darkness the RS altitude of 1000kms allows its signal
to penetrate down through the ionosphere easily. It can then chordal
hop skimming the ground and see the underside of the ionosphere 47
degrees away ie approx 5200 kms away, perhaps under the sun.

In many cases signals are very rough sounding showing a bandwidth of
up to 100Hz on an FFT display. Equally obvious, the signal path is
rarely continuous , exhibiting marked doppler shifts/jumps of up to 50
to 80 Hz in an irregular fashion, such that the FFT frequency spectrum
display resembles thick overlapping slates/tiles, on a sloping roof.