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.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)