Radio antenna

ESP47 said
I'm an RF technician myself who has swept thousands of antennas but I don't have experience sweeping antennas in the AM/FM range that our radios use.

The ground plane is absolutely vital for transmitting and while it's important for receiving, it's not nearly as important. In our field, we always say you need your antenna dialed in to be able to transmit correctly but you can basically receive with a coat hanger. I've tested plenty of antennas with pretty sketchy ground planes and it really just depends on the antenna, the frequency and whether or not you can manipulate the attachment to make the ground plane better.

In this case, I'm curious if @70Duster340 tried my suggestion and just ran a couple alligator clips from the base of the antenna to good grounds on the chassis to see if that would wake the antenna up and allow the radio stations to come in.

That's been my experience too. As long as you had a good ground on the antenna housing, a coat hanger mast would work just fine. Since close to 100% of all cars just receive and not transmit through their antenna, it sounds to me to be a total nothing burger regarding ground planes and other technical stuff. I remember when I had my fiberglass body dune buggy with not only an AM/FM radio, but, a CB as well. I had two different antennas over the years. The first was just a regular telescoping tri-band type that came with the CB package. It was just mounted on the "hood" section of the body. No metal anywhere close to it. Worked just fine as long as I had a ground wire attached to it. For safety reasons, I changed to a lighted rear whip antenna for the sand dunes. It was mount in the rear section of the fiberglass body (no metal there either) and also had a power wire for the light on top. Worked fine there too. Now, could it have been tweaked to the nth degree by using a better location for optimal transmission and receiving? I would imagine so, but, I wasn't relying on it to defend a country.