Knew a guy who was on subs in the Pacific from 1941, started in an SBoat, ended in the Fleet boats with Radar.
He described Radar very simply. You have eyes, that's like your microwave radio receiver.
Your Radar Transmitter, that like a flashlight.
In a dark room, everyone with eyes open, can tell when you flip that Radar on.
Radar Receiversas mostly passive devices, while Transmitter is active, broadcasting Radiowaves.even though not on the exact wavelength, you will get indicated signal that someone is broadcasting, and can tune to get an estimated heading.
So he said the game was, don't turn on the Radar Transmitter till ready to open fire