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

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