Satgen197 Getting the Satellite DX Edge by GM4IHJ 2nd Jan 1993 The BID of this msg is SGEN197 Please use that BID if you retransmit it. HF sat operating on Mode K 21 MHz up and 29 MHz down is inexpensive and, fun. You can if you wish , use the sat only when it is overhead UK , and get good DX into Russian on eastern orbits, and DX into Eastern USA on western orbits. But if you want to go further you have to be able to exploit the " over the horizon " contacts which occur when RS12's signal is assisted by HF ionospheric propagation. RS12 is presently favouring two types of propagation .One we think we understand reasonably well involves access to and reception of the satellite when it is below the UK western and southwestern horizons over a sunlit North Atlantic as seen from UK . NM7M who gets the same mode up in the Pacific Northwest of USA, when the sat is south of him over the Pacific, accounts for this propagation as being due to the passage over the stout F region over low latitude and equatorial regions. An initial group of these signals occurs minutes or so after Loss of Satellite at the UK horizon, using one ionospheric hop. There is then a break of perhaps 8 minutes before contact is restored via two ionopheric hops, with signal sometimes trackable down to Antarctica. Less easy to describe are the sub horizon contacts made when RS12 is over the night side of the pole coming up the North Pacific and swinging over Arctic Alaska before coming in range of UK as it crosses Greenland. There is no sunlit F layer to help these signals, which are occuring in the Northern mid winter when this region gets no Sunlight . NM7M suggest we are getting some sort of polar ducting, a signal mode never previously reported as far as I am aware, but it must be something like that. Interestingly enough these polar signals are usually reasonably steady , whereas the sunlit equatorial ones have long deep fades. But be warned, the signals are never strong in either situation. So CW operating is desirable, and there is no substitute for good antennas - Sloped Dipoles or Beams with pre amplifiers on the antenna. Careful tuning also helps. Having a modern computer tracking program which accurately calculates doppler shift as calibrated against your station receiver can be a big help because these signal are frequently inaudible on all but a narrow audio band around 600 to 800 Hz. Audio filtering also helps, but beware Crystal filters. The pulse components in most modern reception backgrounds can make a crystal filter ring, drowning any signal. Much better are digital filters (QST Sept 92 p43), or the continuously adjustable filters found on JRC receivers. Equally useful is IF passband shift. You set the passband shift over the edge not over the middle of the IF passband and get quite a lot of noise relief from computer QRM . You cannot control the kids next door and their micro or toy qrm but it also helps even with relatively quiet IBM micros to inhibit the cursor action Eg insert something like :- 9558 LOCATE 21,1:print"Press any key to continue" 9560 X$="":WHILE X$="" 9562 X$=INKEY$:WEND 9566 INPUT " Next choice GCmap Dop Nudate Time ";CH$ Which delays the action of a noisy cursor until you want a menu change. Last but not least remember that RS12s orbit moves slowly westwards each succeeding day. So do not expect DX patterns to last for more that a fortnight or so. Good Hunting de John GM4IHJ @ GB7SAN