I've seen references that at least by the latter part of WW2 oscillographs were being used to identify transmitters and/or ops. It should be possible to deduce chirp, rise time, fall time of signals, all of which characterize the transmitter, as well as element spacing and other characteristics that help identify the operator, from oscilloscope snapshots of the demodulated audio at various sweep speeds.
> On Jun 21, 2016, at 7:02 PM, Alan Melia <alan.me...@btinternet.com> wrote: > > TX "fingerprinting" in WWII > You seem to be forgetting that there were very few of the sophisticated > digital timing systems were available 75 years ago. Traffic analysis was > started early in 1938 or even before. By 1939 we knew all the nets used in > Europe and had "Y" ( a corruption of WI, Wireless Intercept )operators > monitoring the nets. Many of these were amateurs and they were allocated to > specific nets and followed them around as they moved. They became very > familiar with the "accents" of operators on their nets, and particularly > before 1939 security procedures were very lax and "chatting" > common-place.....but it was all aural. > > I suspect serious transmitter parameter logging was not done before the cold > war when spectrum analysers, or at least pan-adapters became more readily > available. To keep a little OnTopic .....you would have difficulty doing this > with a BC-221.!! :-)) A crystal clock of this period was at least one fully > utilised 6foot 19inch rack (there is one at Grenwich.) > Alan > G3NYK > > > Alan > G3NYK > > ----- Original Message ----- From: "jimlux" <jim...@earthlink.net> > To: <time-nuts@febo.com> > Sent: Tuesday, June 21, 2016 10:02 PM > Subject: Re: [time-nuts] Measuring receiver... > > >>> On 6/21/16 11:28 AM, Brooke Clarke wrote: >>> Hi: >>> >>> During W.W.II there were secret methods of "fingerprinting" radio >>> transmitters and separately the operators. >>> I suspect the transmitter fingerprinting involved things like frequency >>> accuracy, stability, CW rise and decay time, &Etc. For the operator some >>> from of statistics on the timings associated with sending Morse Code. >>> But. . . I haven't seen any papers describing this. Can anyone point >>> me to a paper on this? >> For "human controlled" stuff, e.g. recognizing someone's "fist", there's a >> huge literature out there on biometric identification looking at things like >> keyboard and mouse click timing - the timing requirements are pretty slack, >> and hardly time-nuts level, unless you're looking to do it with mechanical >> devices constructed from spare twigs and strands of kelp. >> >> There have been a variety of schemes for recognizing individual radios by >> looking at the frequency vs time as they start up. Likewise, it's pretty >> easy to distinguish radar magnetrons from each other. Not a lot of papers >> about this, but you'll see it in advertising literature, or occasionally in >> conference pubs (although I can't think of any off hand). There was someone >> selling a repeater access control system that was based on the transmitter >> fingerprint. >> >> But the real reason why you don't see any publications is that this stuff is >> pretty classic signals intelligence (SIGINT or MASINT) and it is still being >> used, and is all classified. You're not relying on Betty the receiver >> operator to recognize the characteristic chirp as the agent's radio is >> keyed, it's all done by computer now, but the basic idea is the same. And >> as with most of this stuff, the basics are well known, but the practical >> details are not, or, at least, are the proprietary secret sauce in any >> practical system. (In a significant understatement, Dixon, in "Spread >> Spectrum Systems" makes some comment about how synch acquisition is the >> difficult part and won't be described in the book) >> >> You might look at the unclassified proceedings of conferences like MILCOM >> and find something. Googling with MASINT might also help. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
