If you’re placing your RPi anywhere near your antenna and powering it via PoE, I would highly recommend doing testing to see if the PoE system is resulting in an increased noise floor. Same goes even if you are powering your RPi via some other means.
I have tested a few of the cheaper PoE injector/splitter units and found that they produce considerable noise on both 2m and 70cm. It is quite likely that many SatNOGS stations are not performing as well as they could be due to use of these kinds of splitters. Putting everything into a metal box may help, but there is still the possibility of noise coupling between PCBs within said box, and even through power rails.
Unfortunately, once installed, it’s not like you can just cut power to the PoE splitter to do an A/B test - as you are powering the RPi from this!
A ‘simple’ test would be to hook the in-situ antenna and SDR up to a (battery powered) laptop, and observe the band of interest. Turn the PoE injector and RPi on and off, and watch for changes in the observed noise floor. If it rises at all, then your station is equipment-limited.
From my experience tuning my three SatNOGS stations, physical separation is the best solution. If you’re running ethernet cable from your station to somewhere else, then I would suggest placing a preamp in a box near the antenna, and running coax instead. It doesn’t matter if the coax isn’t ultra-high-quality - as long as the preamp gain overcomes the cable loss, the system noise figure will not be degraded significantly, and system noise figure is what determines your stations sensitivity.