OP = Original Poster, IEyou

When Radio control was in it's infancy, IE tube radios and only a single channel that controlled a rubber escapement for rudder control, it was all on the ham frequencies. Sometime around early 60's, Citizen band radios came about and it was a wild free for all as guys had them in their cars, the truckers really liked them to keep track of the Smokey's. and later with the illegal power amps, it was the "free Long Distance telephone that every one got to listen to" RC planes were on the same frequency, IE 27mhz AM. Soon, the Citizen Band was a free for all and the planes didn't fare very well. A new band was set aside for RC use, actually two bands.

When the FCC sat aside frequency's for RC use, they designated the 72mhz band for aircraft only and 75mhz for surface (cars, boats, Robots, etc) When 2.4ghz was authorized a few years back, there were enough band width and with the designof the equipment on the band that frequency control on the flight line wasn't and issue anymore. There are other bands, IE a few channels set aside in one ham band for use by Ham Radio operators.

I'm open to correction and or new information that I didn't post. I was just and interested bystander for many of those years.

Don