Eventually, decided to try using it to talk on 10m, with a tuner, which worked fine (of course); really did not need the tuner, but brought the SWR down a bit (from about 2:1 to 1.5:1). Then tried 6m, which resulted in a much too high SWR reading (off scale), even with the tuner.
Just for kicks, I tried 2m (no tuner), not expecting anything usable. However, the SWR meter indicated 1.2:1. So, I tried 440, which resulted in a slightly higher, but acceptable SWR reading.
I do not think that should work, not normally, but the SWR meter seems to say that it does, and have made several contacts on 2m that stated it sounded okay.
Admittedly, I have a somewhat nonstandard setup (different size coax, barrel connectors, …), so that could be partly why.
Just find it amusing to tell other hams that I'm talking to them on a CB antenna. 🤓
—
a little more info:
The antenna is located approx. fourteen feet high, on a PVC pipe, between two mobile homes (house trailers), under a dense canopy of various deciduous trees.