[GreenKeys] Brecom system

[KFIam640@aol.com]

In a message dated 4/23/03 13:44:22 PM Pacific Daylight Time, bstrang@iac.net 
writes:

> Someone was just telling me about the "Brecom"
> system developed in or around WW2.  It involved
> hidden FSK keying on clear-channel am broadcast
> stations in Cincinnati (WLW) , St. Louis, Des
> Moines, Salt Lake City, San Francisco, Los
> Angeles, Dallas, New Orleans, Atlanta, New York,
> and Pittsburgh.
> 
> They keyed the carrier of these stations by two
> cycles at 30wpm.  It was unnoticeable by regular
> listeners.  This chain of stations was a backup if
> national telephone communications failed.  It
> apparently wasn't needed for the design purpose,
> but they kept chatter on the system to maintain
> readiness.  Apparently used model 15 machines, but
> my informant wasn't certain.
> 
> Anyone have more information on this?
> 

I am also interested in learning more about this.  Two and a half years ago I 
retired from the position of Chief Engineer of KFI in Los Angeles, after 
being at KFI from 1976 to 2000.  I remember hearing of the FSK on KFI back in 
the fifties and tried to copy the signal but at the time I did not have an 
FSK demodulator that would handle the narrow shift.  Nor did I know when the 
tests were on the air.  I don't believe the tests ran all the time.  One of 
the old timers at KFI told me the shift was plus and minus five cycles.  When 
I arrived at KFI there was a model 19 at the transmitter which had been used 
for this system.  There were also some FSK modifications in the KFI 
transmitter that was in the use at that time.  I later replaced the 
transmitter so the FSK modifications went away.  I never did see the Model 19 
wired to the transmitter.  I always assumed it was a standard Model 19 
Teletype machine that ran at 60 WPM, 45 baud five level Baudot code.  I never 
took time to power up the machine to check the speed.  In the eighties I 
installed a solid state 50 kW transmitter at KFI.  During the clean up of the 
building the Model 19 was dumped.  It happened without my knowledge.  Had I 
known I would not have let it go to the dump.
       I never did see any evidence of how an incoming signal would be put on 
the air.  Based on what I saw it would appear that the Model 19 was used to 
run a test loop tape of some sort.  I don't remember seeing any type of off 
air FSK demodulator for receiving an incoming signal.  Though there was a 
Hammarlund general coverage receiver at the KFI transmitter.  I remember 
someone telling me that the plan was to receive the signal from another 
broadcast station for relay.  I was under the impression that the 
transmissions were to be received by military ships at sea in the Pacific 
where KFI would have a good signal at night.
       I believe the tests on KFI continued into the fifties.  I acquired my 
Model 26 in 1955 and that was about the time I heard of the KFI tests on FSK. 
 I hope someone has more information on this interesting piece of history.

Marvin Collins, W6OQI
retired Chief Engineer, KFI Los Angeles


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