I have a 73 vert with AC, 4 manual tran, PB, PS, small block. PO changed out the distributor to MSD electronic system. I removed the aftermarket junk radio and installed the correct year Delco Stereo Radio and Convector, with the appropriate speakers. The radio sounds fine, I do hear a little whine when I first turn on the radio, but no big deal. The other day, I am sitting in the car waiting for the wife, and turn off the engine. I turn the key to Accessory, and all I heard is static, really distorted sound. I restart the engine, when she finally returns, and the radio is fine. I don’t see any capacitors on the turn signal relay, or under the hood. Any help would be appreciated. It seems backwards that the sound is ok when the engine is running, and terrible when on accessory (battery)?

Since the static only happens when your key is in the Accessory position, I suspect that the electrical contact there may be dirty or a loose wire connection causing the static. This may be the result of little use in that position compared to the On position where the radio sounds fine. Electrical contact cleaner spayed on the contacts may cure the problem. You may have to take the steering wheel off to get a better look at it and also tighten any loose wires.
Fran

I will take a look at the ground on the antenna. There is tons of undercoating under the car that will need to be removed. The problem with the key switch could also be the culprit, since it seldom used. I had to tear into the steering column to repair the horn contact located on the turn signal switches, and I was afraid to go any further to investigate the key “left in the ignition” contact. If I get my courage up, maybe I could fix both items at the same time. Thanks for everyone’s input.