+1 on ensuring everything is grounded correctly.
You could either be picking up noise through the power side or the satellite/box could be picking up RF noise through the air.
If it's the power side, ensure your lights and satellite system are grounded correctly. As in, make sure your cables are wired correctly and your outlets are properly grounded. Some houses, (like mine) have 3 prong outlets where the ground pin is not connected to anything or there is no ground wire routed to them...so no groundie. I'm guessing the last homeowner on mine tried to be a do-it-yourselfer and screwed it all up. You may have a similar problem. I think you can get a quick outlet checker at home-cheapo that will tell you if that's the case.
If it's an RF issue, having the appropriate coax cable with proper grounding should solve that problem. So basically, try a new coax cable. Just make sure it's the proper type as there are different grades of cable out there. You should be able to see something printed on the side of the cable you can use to compare. Or on a basic level (and relatively inaccurate) check the thickness of the cable for a rough guess. Older ones tend to be thinnner and won't work as well.
Hope that helps...