I'm installing a 1972 delco am/fm into my '68 burb and have a question about the antenna hook up. Does anybody know how the antenna hooks up on these radios? It doesn't have the typical pin plug in type on the back of the radio. I have power to the radio but no sound. I cannot figure out the antenna. Also, should it be that the radio won't power unless the antenna is plugged in even with a power supply wire to the radio already???