Hi Keith, Another kind of neat thing you can do with heterodyning. A private telephone voice signal can be added to a received public radio broadcast signal at one end of a phone conversation, sent along the wire as semi-musical noise, and decoded at the other end by subtracting the same, slightly delayed for syncronicity, radio signal from the mess, leaving the voice signal. Both parties just had to agree beforehand, which station they would use as the carrier. Low tech spy stuff, fairly simple, very slick. Who knows, the system may still be in use somewhere today. Interesting observation that we are signal heterodyning when we tune. I hadn't thought of that, but I like it. Does that mean we can raise our rates, and get a RPH PTG designation to list after our names? We could start our own tuning heterodynasty. Ron N
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