Satgen 529 Old Soldier Oscar 10 by GM4IHJ (BID SGEN529) 1999-05-15 Next month Oscar 10 will be 16 years old. Planned for a high inclination elliptical orbit , it never got there. Its first orbit adjustment firing after release from the Ariane launch vehicle, turned out to be its one and only burn. Placing it in a low inclination orbit going out to a distant apogee far from earth , but returning to a relatively high altitude perigee orbit low point , which causes it to spend a great deal of its time in the Van Allen Radiation belts. >From the start, the mode L transponder was very insensitive and never available for low power communication . But its mode B transponder 435.1 to 145.905 MHz LSB up, USB down , worked well and gave several years of excellent long range communication. Although its apogee high point flapped cyclically. Being in the northern hemisphere for two years , then in the southern hemisphere for two years before returning north. However in 1987 the good times were over when the satellite ceased to obey ground commands. Contrary to expectations however Oscar 10 did not die . It remains fixed in mode B, as its power supply fluctuates slowly . Such that it is operational for a few weeks , then it goes into hibernation for a few months before gradually returning to duty for another operational cycle. When operational, its performance is less than perfect , but usable with care. The satellite has gradually lost its spinning motion which kept it pointing in a fixed direction, and it now tumbles slowly in space . This tumbling produces a rather odd fading pattern to its down link. A pattern which varies somewhat depending on the satellites aspect with respect to your station location . So that at any time stations far removed from one another can be experiencing quite different fade patterns. Seen from a listening station the satellite appears to complete one swing roughly every 145 seconds. During this swing the triangular geometry of the satellite produces 3 fades roughly 48 seconds apart. Fades which at some aspects produce a 10 dB drop in downlink, but at others result in a complete loss of signal for 5 or 10 seconds. So do not be surprised if your contact ask you for a repeat of something which you heard perfectly. With a sophisticated station you can receive the unmodulated beacon on 145.810 MHz + or - doppler and use another receiver for communication , timing your overs to " miss " the beacon fades. A trick which is even easier if you can monitor the beacon on an FFT display , allowing you to see when the fades are coming and anticipate them. CW is clearly superior to SSB , with stations centering around 145.885 MHz downlink. The sideband transponder is a frequency inverter to reduce doppler effect, so you should use LSB up , listening for USB down near 145.91 . There is plenty of good DX providing friendly voice to voice communication with enthusiastic operators, proving once again what real amateur radio is about, and showing how different things could have been , if Amsat had concentrated on simple mode B and S, Molniya orbit sats, and persuaded other sat builders to do the same.