......RAF pilot in the early 70s telling me that he had flown an aircraft with a fixed crystal set which could only transmit on a single or a limited number of frequencies. A civilian ATCO had told him to go away and not come back until he had a proper radio.
Mind you, that could have been the RAF Twin Pioneer pilot who flew my Prentice to South Africa from Sharjah in 1967. It had a 4 channel crystal VHF set mounted behind the pilot's seat. Adequate for normal training operations, perhaps, but on longer trips, eg Gatwick to Sharjah and on to Durban, there was a box of 70-odd crystals to cover all eventualities on route.
When ATC said, for example, "call Tower on xxx decimal x", but the frequency was unexpected and therefore not one of those set up for the sector, the pilot would reach behind the seat with the right hand while flying with the left, switch the radio power off, remove a redundant crystal by feel from its socket, replace it with the required crystal from the box, then unplug the antenna and replace it with a plug wired to a 12V light bulb (ie the 3ft piece of wire was soldered to the bulb terminals), switch the power on again, then press the PTT on the stick with the left hand and operate the antenna tuner on the set with the right until the bulb glowed, then put the antenna plug back, then press the PTT and call the station required. On a good day this would take about 2 minutes. In poor visibility and turbulent conditions it would take rather longer but this was offset by the fact that the aircraft flew quite slowly; on a long final approach one only needed 2 - 3 miles to "call Tower on xxx decimal x".
Nowadays, I understand, you simply rotate a knob, or even just enter it with a keypad, and the new frequency is displayed in figures on a little screen. Modern rubbish. Just more gizmos to go wrong.