While I was operating on 40 m for Field Day, I noticed a higher SWR than when I first set my antenna tuner for the band. This happened, of course, because I was in a different part of the band, but I hadn’t done enough HF operation to expect the result automatically.
80 m is famously so wide that the phone segment of it gets called “75 meters” because the difference matters for antenna design.
I’ve heard that what matters for antenna and electronic design is the relative bandwidth — the ratio of the low and the high ends. I’d like to see what this ratio is for all of the amateur bands, and just how much of an outlier 80 m is or isn't.