RB wrote:

snip
I think the metal threaded socket the antenna screws
into is turning in the plastic coupler body.

Now what?

Is there a visible gap between the socket and the body? If so, dribble
a little crazy glue (cyanoacrylate?) in the gap in the hopes that it
will glue the two outer parts back together without gluing the two
pieces you want to come apart together also. Or may you can drill a hole
in the plastic and/or grind or whittle some of it away to get a place to
the pieces glued back together.

This is sort of destructive disassembly technique, you'll have to fix it
later if you can get it apart.

You've heard about GPS, right? :)

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)