Satgen 466 Space Propagation Pt5 by GM4IHJ (BID SGEN466) 98-02-28 Continuing discussion about the effects of Sporadic Ionisation of the E layer of the ionosphere (SpE) begun in Sgen465. Mention should be made of the fact that while many satellite operators are taken by surprise , when SpE interferes with their satellite operations, there is no real excuse for this. Noting that most ham shacks contain equipment capable of giving more than adequate warning of the presence of SpE. First among these warning aids are the 6m and 2m receivers. Both bands are well served by beacons , and regular daylight surveys on the frequencies of beacons located between 500 and 2500 kms from your station, should soon reveal evidence of SpE when these normally quiet frequencies suddenly burst into life. Equally useful as warning devices ( although actual frequencies appropriate to your location vary slightly ), are the low VHF TV stations ( Africa and Europe West 48.25, Europe East 49.75, and USA 55.25 MHz approx), and the VHF FM stations (East Europe around 72 MHz, the rest between 88 and 110 MHz). Secondly , one should not forget the calendar. The seasonal nature of temperate latitude sporadic E, means that it is weakly present in mid winter, very strongly present in mid summer, and almost completely absent from February to April and , from September to November. Experiments. Getting a better understanding of SpE , using experimental techniques is not easy. It is necessary to first detect the onset of SpE using the beacon TV and FM stations reported above. Then if you know the location of the beacon,TV or FM station, it is usually reasonable to assume that the actual cloud of ionised material responsible for the SpE propagation , is located halfway between your station and the station you are receiving via SpE. When several stations are present via SpE , as is often the case, it becomes much easier to define the SpE location and its probable extent. Then knowing the Lat/Long where the SpE is located, and that it is at 80 to 100 kms altitude, you can then estimate when the line of sight between any satellite and your station will intercept the SpE zone , allowing you to record what happens to the satellite signal. In practice with satellites at heights up to 1000 kms the longest period a SpE cloud is likely to affect your signals is perhaps 5 minutes . So you rarely if ever lose a complete pass to SpE. At IHJ, the number of opportunities for carrying out this kind of experiment has been increased by using commercial satellites as well as amateur satellites as targets. Weather satellites on 137.5, 137.62 and 137.85 MHz are very good targets , as are the Navigation satellites between 149.91 and 150.1 MHz, plus Orbcom downlinks on 137.7 and 137.68 MHz. All provide good aural and sig/noise evidence of the effects of SpE, with OrbCom being wideband whereas the other signals are narrower. In addition, if you have Wefax picture reception the NOAA and Meteor satellites mentioned above give excellent pictorial records allowing comparison of SpE days and Non SpE days.