There are numerous sources of information on ground loop hum on the net (Google is your friend). Here's one that has good information (if not the best spelling or grammar):

http://www.epanorama.net/documents/groundloop/

I would recommend a component by component, connection by connection test to definitively determine the source of the hum. Start with external connections(CATV, Satellite Antenna, etc.). In the case of the satellite box, first disconnect the coax antenna cable coming from the satellite dish to the receiver. Is the hum still there? If it's gone, the dish may not be properly grounded. Try reconnecting with the isolation transformer, but even if that fixes the hum, HAVE THE DISH PROPERLY GROUNDED. If the hum persists, the source is downstream and possibly isolateable with a line level isolation transformer available from Blue Jeans Cables. You'll need to test each component individually where it connects to your processor, removing the line level connections one component at a time.

Take a look at this thread on Audioholics; it seems that Hughes satellite receivers have been known to induce hum due to some issues with their power supplies. A properly grounded, dedicated circuit may help, but there may be more to it. I'm sorry I can not be more helpful but ground loop hum is hands down the most frustrating thing I have EVER had to troubleshoot in my systems due to the huge number of potential variables. Also, I have no first hand experience with Satellite TV.

This time I got off easy thanks to two factors: New, properly grounded construction and a single source of hum (CATV).

Be persistent, be safe, and don't give up. Hum is almost always completely correctable.