You won't get noise, with shielded wire, and grounded, try grounding at the dish end only. All sat ribbon cable is that way I never had a noise issue using a reed switch, von wise made a special double magnet wheel for KU, I might have some laying around hall switches die too easy when lighting is around, same with optical sensors.
The only issue I have seen from what your thinking is noise, is a bad house-ground or the AC power outlet to your receiver is plugged into is an outlet with neutral and ground, wrong bad house grounds will cause issues when the dish moves and your furnace or well pump or anything that draws a lot of current, is turned on while the dish is moving, you get a ground loop, in your reed switch circuit and the dish gets off position, the house power tries to use the dish ground.
Fix your house ground, I saw it happen at least 3 times doing C-band, in all cases, I was perhaps the 3rd or 4th guy called in the others were not electronic people