Satgen 509 Sat Fingerprints Pt4 by GM4IHJ (BID SGEN509) 1998-12-26 The fingerprint of a simple continuous wave radio beacon can be a firm line , showing a stable transmission . If it is keyed the line becomes slightly broadened at key down and may ripple slightly due to transmitter relay bounce. At key up the line will simply disappear. To avoid confusion if interference occurs during the transmitter off phase , and to give smoother transmitter performance, many satellite beacons use two tone frequency shift keying . Providing a smooth received signal changing in radio frequency , one frequency for mark key down , another for space key up. In practice the frequency shift can be anything from 120Hz to perhaps 9600 Hz , and from the point of fingerprinting this is highly diagnostic because the frequency change satellite to satellite is rarely an exact multiple of ten. Careful checks of say the different frequency shifts in a set of satellites orbiting in a pattern or constellation can provide direct identification of individual members. Many satellites use slightly more complex beacon or telemetry keying. . Popular choices are :- 400 bps as in some Phase 3 satellites. 1200 bps Biphase keying as in Pacsat, Webersat, Lusat and several other amateur radio store and forward satellites. 2400 bps Quadrature phase shift keying is preferred for use with geostationary communication satellites. Whilst a third group of amateur radio satellites use 9600 bps employing Frequency shift keying. These choices have a marked effect on the appearance of the satellites fingerprints. Oscar 13 engineering beacon produced two discrete sets of signals 750 Hz apart. Each set had 3 to 5 sub carriers spaced 50 Hz apart going on and off in a very distinctive pattern. Pacsat ,Weber and Lusat transmitting a Biphase Shift keyed signal bpsk produce a fingerprint with 3 or 5 main carriers spaced 1200 Hz apart , with the central carrier flanked on either side by 7 sub carriers spaced 50Hz apart. When keyed one sub carrier broadens. Fuji 29 also transmits bpsk with 5 carriers 1200 Hz separation. But the subcarriers around the central carrier are unevenly spaced. Uo22 and the Koreasats tranmitting 9600 bps simply do not appear on a narrow band finger print display . To "see" them properly you have to view an audio band about 20 kHz wide . Orbcomm satellites can be seen on a display 2.7 kHz wide but do not expect to see clear distinct carriers. What you get is a series of highlighted sections of picture noise separated by bands clear of noise . Bands which curve down the diplay as the signal dopplers. Wefax satellites of the NOAA series show 2 broad dopplering carriers 750 Hz apart. While Russian Wefax Meteor Leosats show a single main carrier bordered by broad indistinct sub carriers separated from the main carrier by about 32 Hz. There is therefore a wealth of various diagnostic features associated with each form of modulation and even with each satellite. Though of the same design Webersat keying is not quite the same as Pacsats, and Lusat optimised for Southern hemisphere viewing usually shows fewer carriers than Pacsat when it is over the Northern Hemisphere.