[CW] MCW

[N6KB via CW]

 The RCA station in Los Angeles, KSE used to run MCW on its 500 Khz
announcements. I don't know what they used but they would come on in
plain CW and the modulation would come up gradually as thought a tube
heater was started. 

Three phase 60 Hz power supply would generate a 360 Hz modulation if the
filter capacitors stopped working. Maybe connection to capacitor was
corroded and resistance went up as the transmitter heated up.

 
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