Check 530 Khz ultrasonic, not radio. No cross talk, very directional.

And yes, some of the IR telemetry was window vibrations. In fact, we had to site acquire using a red beam to before we could switch. You gotta switch because the bright red dot is a giveaway.
_________________________
The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)