So, hey guys, I bought a NanoVNA and started prototyping some filters. One I liked very much was the helical ressonator. I shared a report on reddit where you can find some measurements.
TL;DR: Built and tuned a 2m helical band-pass filters. Results were great, < 0.8dB insertion loss across the band and >60dB rejection of FM band. Great return loss too. The filter doesn’t quite cover NOAA to the end of the 2m band, but that’s okay because receiving NOAA sats is not my goal here. It’s actually better so these birds don’t overwhelm my receiver.