Satgen71 DOVE IS BACK : Pacsat Signal Fading by GM4IHJ 6th August 90 DOVE IS BACK ON receivable on standard terrestrial packet radio station receive rig tuned 145.825 1200 bps Recent packet correspondence has asked the question - "Do you get steady signals from the Pacsats "? The following answers cover my personal experience , to date. Uosat3 Oscar14 435.07 has a very strong signal, and I have not noticed any reception problems . Pacsat Oscar16 437.025 is highly variable. When the sat is providing power to both its UHF and S Band downlinks, its UHF signal is weak. When S Band is off, UHF is a good signal most of the time. Webersat Oscar18 437.1 , uses a form of wideband Raised Cosine modulation which is always difficult to tune , but its signal strength is quite steady. Lusat Oscar19 has a very variable signal. The Raised Cosine signal on 437.125 is much easier to tune than Weber but both it and its Manchester modulation counterpart on 437.15 suffer deep fading and generally low signal levels at times. Note, Lusat uses either RC or Manchester, not both at once. JAS1-B Oscar20 435.91 is highly variable with a fade pattern all its own. Some days it is a nuisance, other days it is not noticable. Horizon Fading. Please note that when any of the Pacsats is near your horizon at AOS or LOS, you will get fading. This is because you are getting a ground reflected signal added to your direct path signal. Sometimes they add in phase, sometimes they do not. A typical sequence produces 3 deep fades 20 seconds apart as the satellite rises from your horizon. Then as it gets higher the ground reflected signal dissappears and fading stops. The same sequence can occur in reverse at LOS end of pass. Ionospheric Propagation. This summer we have also had poor downlinks on UHF on several days on each of several Pacsats as they went past my station one after another. The effect usually lasts for about half the in range pass or less and is due to Sporadic Ionisation of the E layer along the line of sight , from the satellite to your station. The presence of Sporadic E can easily be checked by looking for concurrent propagation of foreign TV signals ( European around 48.25, Russian around 49.75 and European around 62.25 MHz ). For anyone interested in propagation, the Pacsat family offer a unique opportunity for multiple consecutive checks of the ionosphere at UHF.