Our UAS Chippies were fitted with the ancient VHF controller which was connected to the suitcase-sized VHF box somewhere behind the rear seat (I think). The controller caused a unidirectional motor to rotate to select the right crystal; going from Channel A to Channel B was quite quick, but from B back to A took a fair bit longer - you could hear the thing whirring and clattering away..
Funnily enough, many years after the frequencies were no longer in use, our aircraft were still crystalled with historic frequencies such as 115.56 MHz and 142.29 MHz etc - utterly useless except for Chippy-to-Chippy!
But putting the full-band VHF set in the Hawk was fun - if you hunted around above 137 MHz, you could find some interesting conversations...
