TL;DR - The CB antenna basically pooped its pants. I've replaced it.
A couple days into the trip, my CB reception and transmission essentially stopped working. My SWR jumped to over 15. The problem - we discovered - was that the wire wrapped around the fiberglass shaft had come unsoldered from the base, essentially rendering the antenna 2" long. We were able to fix that on the trail - solving my problem in the short term - but then on the way home, a strong headwind broke the fiberglass portion of the antenna. Or rather, separated it from the metal base.
I've already ordered and received a replacement antenna (FireStik FL3-B w/adjustable tip) that will solve all the problems.
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