Many thanks to SWLing Post reader, Gary (WN9U) who writes:
Just an FYI comment about the narrow filters NOT staying on while tuning. I read about the similar problem that you encountered during the initial testing of the PL-880.
While tuning CW stations with the 500 Hz filter turned on (fast or fine tuning), the filter would always revert back to the 3.0 wider setting. It had never done this before. I tried several resets with no cure.
After further testing I found the fix: I had turned on the Hidden Menu Noise Reduction (switch 6) and did not realize it was on.
After turning off the Noise Reduction, I was able to tune with the narrow filters set at any band width. Evidently, the filter opens up to 3.0 when tuning with the Noise Reduction turned on & reset does not turn off this function.
Thanks so much for the tip, Gary! I’ll add this to our (still) growing list of PL-880 hidden features and tips. Seems there’s always something to discover on the Tecsun PL-880.