[MRCA] Disassemble this connector?

[W2HX]

Anyone know how to disassemble this connector?  I turned the knurled ring counter clockwise and it wouldn't budge. What is the trick? This is for a VIC-3 system.
https://w2hx.com/x/What-Is-It/20210801_202503.jpg
https://w2hx.com/x/What-Is-It/2.jpg


73 Eugene W2HX
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