I wondered that, myself so I disconnect all grounds including the antenna and tested the grounds for the radio's ground wire and at the bracket that holds up the rear casing of the radio with a test light. I put the test light clip on the positive power source and touched the test light tip to the bracket and the light came on. Then, I touched the tip to the screw I am using for the radio's ground wire and it came on again. Since the antenna wire itself can ground it, I left the casing bracket and the ground wire disconnected and plugged in the antenna cable. The radio lit up and began to play. So, as near as I can tell, all 3 grounds are working properly. This really sucks but, like all other problems, I AM GOING TO BEAT IT! Somehow, anyway!