[time-nuts] Measuring receiver...

jimlux jimlux at earthlink.net
Tue Jun 21 17:02:21 EDT 2016

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.

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