Satgen 20 16th August 89 Mystery satellites on 435.974 MHz. Most readers will know that one of these satellites appears to be the Polar Bear arctic communications experiment, but several users are puzzled as to why it switches off as it leaves the Arctic. The reason may be hidden in the title " Communications Experiment ". US bases in the arctic are too far from civilization to get terrestrial TV, and they cannot see the TV geosats because they are too low on their horizon. So one test proposed for Polar Bear is " Time Compressed TV" - a one hour TV show compressed to a ten minute transmission burst. As PB crosses the Equator, it receives this time compressed TV signal from a geosat. Then as it passes over the US arctic bases it down loads the TV to them during its 10 to 12 minutes in range. The arctic ground stations can then decompress the TV back to a one hour show and then transmit it over the local Armed Forces TV network. Naturally PB must switch off its noisy beacons as it crosses the Equator, so that it can correctly load the very wideband time compressed TV signal. RS14 The proposed Russian mode B 70cm up 2m down orbiter scheduled for a mid 1990 launch is excellent news. This correspondent and other ancients who enjoyed Oscar 7B ten to twelve years ago, need no reminder of this, but for those who have not tried mode B in a low earth orbit, it will be much easier to access than the 36 times longer range Oscar 13. It was also good to hear that Leo UA3CR was able to attend the Amsat Colloquium and bring this good news in person. Rudak West German Radio Amateur are discussing a possible opportunity to fit their Rudak packet equipment in RS14. This could mean another excellent FO12 1200 bps compatible modem packet system, for satellite experimenters. Astra TV Geosat On Wednesday 9th August the pictures in GM were hopeless. Virtually every Astra channel needed retuning. Sky, Sky News, Sky Movies had changed frequency and polarisation V to H MTV and Supersport had changed frequency and polarisation H to V and Eurosport had changed frequency. In addition all channels had sparklies until the polarisation skew was reset to a new position. I am still not clear what RTVL did. I heard an announcement after the fact that Eurosport had changed frequency, but I am not sure what the sequence was on the other channels.Pictures are , once again, very good, but I hope RTVL do not make a habit of this. It is all very well for a household like mine with its on call itinerant TVRO hacker, but my pensioner friend down the village had no idea what to do. Another Mystery Some time ago Amsat asked all users to keep off Oscar 13 mode L for the day, so that they could investigate some interference on its downlink. I decided to join the experiment and listening on my best mode L downlink I noted one odd feature. The downlink was empty of obvious signals , but when ever I turned my aerial away from AO13, the noise level went down. Intrigued by this I batted my aerial back and forth across the satellite position in elevation and azimuth, and found I got 2 dB rise in noise as I pointed directly at the satellite. Is it transponder noise or is it some retransmitted ground signal on wideband. I think it is transponder noise. Anyone know for sure ? 73 de GM4IHJ 16 Aug 89