Well, with antenna electrics, I usually find that things cease rather abruptly, usually when a fuse blows, a wire loosens or breaks, an internal circuit component fries, or a switch fails to connect a contact. The trigger for the antenna comes off the dash switch. Have you tried playing with the switch?
I agree, either loss of power or a broken ground is the likely culprit. You'll have to do a process of elimination to isolate the problem.
Since the antenna plug is the easiest to access, I'd start there, both by using a multimeter or test lamp to confirm power and ground from the harness side, and applying 12V to the antenna itself.
Of course, it could be mechanical, as in a broken part inside the unit too, and these do break just as suddenly as an electrical connection. That doesn't sound likely in your case though...

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1986 560SL
2002 Toyota Camry
1993 Lexus