Satgen 506 Sat Finger Printing by GM4IHJ (BID SGEN506) 1998-12-05 The military term ELINT = Electronic Intelligence encompasses a set of equipment and procedures that have been actively employed for many years. Many of these practices could be usefully employed by radio amateurs , but there has been very little published by way of guidance as to how they can be deployed in a radio ham shack. Identifying other peoples traffic and decrypting their software codes is only a very small part of this subject, which goes back to Marconi and can include everything from modern digital signal processing down to the simple pleasure of listening to a good fist on " Straight key night". Indeed ELINT started as an exercise in operator identification. Every operator of a morse key has a distinctive pattern/rhythm , and this may be further modified by the keying characteristics of his transmitter. Nearly 80 years ago the military had a marvelous device consisting of an old fashioned green trace, gas filled cathode ray tube, with a box shielding the face of the tube from outside light. The signal was fed to the Y plates of the CRT so that the spot shifted up and down , and motion along the X axis was provided by 35 mm film run at high speed across the face of the tube. Agricultural it may have been, but the developed film provided a permanent record of operator and transmitter characteristics. Which could be compared week after week to track their movements if the operator was mobile Eg in a warship. Say a new battleship was being built . Careful listening would produce records of all its operators and all their transmitters as they set the ship to work before leaving harbour. If subsequently one of these transmitters and operators fists appeared to come from a Norwegian fiord, the Elint listeners would spot it. Even if the operator used a small low powered Uboat transmitter provided for emergency purposes, used in this case in an effort to stay secret. This scenario enacted in 1941 eventually ended with the sinking of the battleship Bismarck. Since then Elint techniques have improved a million fold, and many of the equipment types and methods employed, are available to todays radio amateurs. Using modern computers, printers and digital signal processing ,amateurs can exploit a multitude of techniques , identifying modulation types, keying characteristics, sideband patterns, and extraneous signal artifacts. The doppler envelope of a satellite can be plotted and permanently recorded allowing extraction of tracking , height, inclination and even likely launch site. Satellites in trouble can be followed day after day and their records studied at leisure, allowing detailed analysis. Every month we encounter new satellites. How can you decide whether you are following the one you want. Even NORAD has difficulty, particularly in the early days of a satellites life, when the separate items of a multiple launch can easily be mixed up. If you have a library of satellite signal finger prints on file, you can have fun trying to do a better job than NORAD. Further details will follow in subsequent satgens.