OK, here's weird one for y'all...

A week or so ago, the radio reception on my 1986 240DL Wagon pretty much disappeared, leaving only static.

The first thing I did was swap the stereo out with another one, but I still had the same problem. So, odds are the radio is fine. Then I took the coaxial antenna wire to a shop and had the continuity tested. There doesn't seem to be any interference...tip to tip conducts, shield to shield conducts and tip to shield doesn't. And, of course, the mast is the mast...not much to not work there?

So what's wrong with this thing?

As a side note, there's one additional problem with the antenna cable. For some bizarre reason, the outboard end of the coaxial cable screws itself into a whole drilled through the body. Either because someone in Gothenburg drilled the hole too wide or because it has somehow gotten wider over the years, the antenna cable will not secure itself to the the frame? How can I remount the wire and mast successfully? I thought about trying a bolt on the other side of the frame, but the firewall pretty well seems to keep fingers out of that area to secure that bolt to the threaded part of the antenna cable.

Any ideas about this?