If I understand you correctly, you are using a on radio antenna upgrade, you are getting results from p25 systems that very well could be out of range in most situations but you're not satisfied with your nxdn trunked UHF reception? I may have misunderstood.
Stick with it, employ filters, invest in a rooftop antenna even if you can't install it on the roof, try a floor lamp and attach a broom handle with the base antenna, with a 10-ft low loss coax. 10 ft is a short run so it really doesn't matter about being low loss, that's just my OCD🙂