alternator whine, 88 vette

The best ground in any vehicle is not the battery in terms of audio, but the vehicle's chassis or frame. The biggest piece of metal that the negative side of the battery is connected to has the highest zer voltage potential or best ground. The older Corvettes were notorious for noise problems. Your antenna whether it is a power antenna or a fixed mast antenna should have a ground strap running from it the the frame rail below it. Make sure it is in good shape and not corodded. A good test for a poor ground on the antenna is to run your engine and listen to a distant AM station. If you get a buzzing noise and hear clicks or pops when you apply the brakes you have a bad ground on the antenna. Try also checking the ground from the battery to the frame. The problem is likely due to a difference in ground between the system and the antenna. This is known as a ground loop and is the major reason for noise problems. Use a meter and measure the resistance to ground between the outer antenna contact at the radio and a known good ground. Have everything turned off when checking this. You should get a reading of less than 1/5 ohms. If you don't repair the antenna's ground or replace the antenna or it's lead cable to the radio.sparky