[time-nuts] Measuring receiver...
jimlux at earthlink.net
Tue Jun 21 17:02:21 EDT 2016
On 6/21/16 11:28 AM, Brooke Clarke wrote:
> 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
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.
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