Satgen 512 Sunspots are Coming by GM4IHJ (BID SGEN512) 1999-01-16 As we begin to see the expected rise in solar activity in the approach to the 2000/2001 sunspot cycle maximum, there is one satellite which is giving an excellent indication of the changes taking place in the ionosphere. RS12/13 has been in fine form recently, producing excellent results , both as a test bed for experimenters, and a very useful platform for amateur satellite communications. >From the experimenters point of view the following is possible :- a. Monitoring the rate of change of Faraday rotation of the signal from the 29.4584 MHz beacon as faraday changes the received polarisation phase . Producing rapid change of received signal strength when the satellite is near your horizon, as against the slower frequency of Faraday induced fades when the satellite is near overhead. b. Observing downlink performance when the signal is descending through a daytime ( high Muf) ionosphere as opposed to a night time ( low Muf) ionosphere. With Maximum usable frequencies now regularly reaching daytime highs near 40 MHz and higher , as American dispatchers on 37.81 MHz FM voice come into Europe most afternoons, the daytime downlink 29 MHz from RS12/13 definitely suffers. >From the communications point of view the above effects can markedly upset qso quality. We are getting a rerun of the late 1970s situation when this problem first surfaced. As IHJ in Scotland tried for months to explain to US East coast operators that he did not have a deaf Xtal set receiver. US operators could only demure noting that they were hearing their own downlink return and IHJs signal 559, whilst for some unaccountable reason he took six repeats to get a simple report. In fact of course both operators had quite good equipment but the hapless European had to listen for a signal chewed up by a high muf solar cycle peak noon time ionosphere whilst the American operator was listening to signals which had come through a low muf early morning ionosphere. A situation which was exacerbated by the fact that AO7 and Ao8 mode A satellites were sunsychronous , following the same ascending orbit timing year after year. Which gave no respite to the Europeans. By contrast RS12/13 is not sun synchronous. So while these asymetrical propagation conditions will occur from time to time , they will not persist for years. Indeed there may well be occasions when the US East coast is looking at RS12/13 through a noon time ionosphere , and the Europeans have a much more benign track through an early evening ionospere with declining muf. Similar ionospheric geometry may possibly affect W1/W6 transcontinental qsos as RS12/13 takes up a track timing at first favourable to one side of the qso . Then a few months later favourable to the other side of the continent/qso.