Synthesized Radios
The Hitec Spectra system is a removeable module type and the freq is selected on two tiny slotted indented pots. The module must be removed to change and no chance of an accidental change while handeling the radio. I beleive Futabas system works similarly but not sure. I don,t know how the Trackers handels this.
The first synth tx to actually hit the market in the US was a Kraft radio sometime around the early eightys or thereabouts. It's freq was selected externally there was major political concern over this at the time and probably contributed to its failure in the marketplace.
John