I had a 2 meter antenna that failed this way once.

Suddenly, no range at all. I put a bird inline, between the antenna base
and the antenna (SO-239 mount) and found 40W forward, nothing reflected, but
my range was about that of my HT on EL power, which is 20mW.

Replaced the antenna with a 1/4w wire, and back in business.

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KC6ETE Dave's Engineering Page, www.dvanhorn.org
Microcontroller Consultant, specializing in Atmel AVR