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.
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