Someone told me that the only way radar dectectors work is if the cop is pointing the radar gun directly at your car and that it will only detect the radar within about 20 feet and that it won't work if he's using the radar gun in a distance. He says that by the time the cop points the radar gun at me, the cop will have already clocked me and that the radar dectector won't pick it up fast enough. He also says that radio towers will interfere with the radar dectector. He says that by the time you buy a radar detector it's useless because the cops are technologically too far ahead. Is this true?