Clandestine data - was: media what died a'bornin'

[Paul Koning]

>>>>> "John" == John Lawson <jpl15 at panix.com> writes:

 John> It is little known (but documented) that, during WWII, radio
 John> station KHJ in Los Angeles ( and undoubtedly many others ) sent
 John> radio-teletype signals by shifitng the carrier a miniscule
 John> amount - I think about 10 htz, and using a very slow baud rate.
 John> This would not be noticed by the average equipment of the day,
 John> and would take very specialized gear to recover, store and
 John> print

 John> But it allowed messages to be sent large distances by powerful
 John> transmitters - completely 'in the blind'.

That's somewhat like the digital time code that WWV sends -- one baud,
on a 100 Hz subcarrier on the regular shortwave signal.  You won't
hear it with a typical shortwave radio speaker, but if you plug in a
pair of hi-fi headphones you'll heard something that sounds vaguely
like a string bass...

Then there are the VLF stations -- there is (or was) a Navy station
around 17 kHz.  I don't remember what they use for modulation.

     paul