Tested my bandpass filter on Mow Cop today. The results were excellent. I could not hear stations calling me until I had the filter inline. The loss on TX was noticable but not severe.
Two distinct approaches are available:
notch filters - advantages: easy to adjust, low loss on TX freq (with 152:145 spacing). Disadvantages: bulky, reject only a narrow range of frequencies (may require adjustment on site).
bandpass filters - advantages: can be small and light, only pass 2m - reject everything else. Disadvantages: small filters have significant passband loss. VSWR deteriorates at band edges. More complex to make.