So it's just historical inertia, over about 70 years? Wow. They didn't hesitate to make our old ELTs and transponders obsolete. Nor the older comm radios (with 100 KHz spacing, 50 KHz spacing, and now in Europe even the models with 25 KHz spacing). On each forced change in radios, the switch to FM could have been made? With some issues during the transition period, of course.

Europe is down to 8.33kHz channel spacing now. That's what caused them to sell all these great used 25kHz radios.

Uli
'AS'