Think of it this way: radio is light. There's a light sensor on a satellite that the BBC shines at. Someone else is shining a really-bright light at the satelli

Think of it this way: radio is light. There's a light sensor on a satellite that the BBC shines at. Someone else is shining a really-bright light at the satellite so it can't "see" the BBC's light through the glare of the other bright light. Kind of like trying to see a flashlight when someone's shining headlights at you. But ... if you're shining a really bright light then everyone who cares to look can see where it's coming from.