Satgen146 Radio Sport on RS12 by GM4IHJ 12 Jan 92 In their original role the RS satellites provided Mode A, 2m up 10m down CW/SSB transponders which could , and still can ( RS10) , be accessed by low power stations using simple antennas for QSOs out to 4000 kms when the satellite is above your horizon. Recently RS sats have also carried Mode K ,15m up , 10m down CW/SSB transponders. Mode K requires standard HF equipment and very simple antennas. RS12 is presently operating this mode, providing :- 1. Reasonable two way QSOs out to 4000 kms when the satelllite is above your horizon 2. Long range ionopheric assisted QSOs around the world, as long as the present high solar flux continues. Where you can actually talk to depends on the satellite track (RAAN) versus the dawn dusk terminator line. Considering this ionopheric assisted activity in more detail. QSOs are achieved when :- The satellite at 1000kms has beneath it an ionosphere which is at least partially transparent to the RS12 15m up and 10m down. So the max usable frequency in any part but not necessarily all of the region of the ionosphere seen from the satellite,must somewhere, be below 21MHz. At these times stations under the transparent ionosphere will hear RS12 clearly. In addition having penetrated down through the ionosphere the RS signal can not only get to local stations , but it can if at moderate to low angles of incidence through the ionosphere take a path above the earth surface to a point on the underside of the ionosphere far distant from the point of penetration. If there the signal encounters a dense ionosphere with Muf above 29 MHz then it can propagate onwards to stations between 2000 and 7600kms approx from the sub sat point Regular DX chasers will recognise that the above conditions are best met when the sat is over the night side , and the distant stations are on the day side of the Earth. So DX occurs when a station in daylight hears a sat in darkness. Eg 1100 ut sat over or near ZL or VK is heard and hears a G OR 0500ut sat over UK is heard in daytime ZL or VK This day/night relationship serves different parts of the world at different sat RAAN. So as RS12 RAAN shifts 54deg/month approx, DX G to VK repeats roughly every 7 months ,with a DX VK to G roughly a third of the way into this 7 month cycle. Prediction is dicey but useful line ups may appear in :- Jan 92 1100 1200 ut G to sat over KL , or 1400 G to sat over JA Feb 92 1100 to 1300 ut slim chance sat over or near VK ZL to G Mar 92 0600 to 0800 ut sat over JA or DU to G Apr 92 0500 to 0700 ut sat over G to JA or VK. Sat over 9H 1100ut to G See RSGB Space Radio HB p91 or Practical Wireless G3IOR for more details. PLEASE NOTE these predictions are based on previous patterns . The rules for them are not entirely clear. Worse still the best recent events involving G3IOR in QSO with ZL , and G3IOR in QSO with other Gs while sat was south east of JA OCCURED AT AZIMUTH FROM G of roughly 340 WHEN GREAT CIRCLE PATH WAS 10 to 30 degs AZ. So swing your antenna for best results as you home in on the RS12 29.408 MHz beacon . 73 de John GM4IHJ@GB7SAN