Ground Loop "Hum" Using BT Modulator

[vts1134]

I've searched this a bit and found a few threads here and there where other folks report having the same problem, but no one reported a solution.
I am using a Blonder Tongue AM60-450 modulator with a dipole antenna to broadcast analog channel 3 throughout my home. The setup has plenty of range for my needs and both audio and video are quite clear. My problem is that I am experiencing a "ground loop", that is I have a white line that "rolls" up the screen from the bottom to the top. I have tried both an off air ATSC tuner, and a BLuray disc player for my sources and they both exhibit the same symptom. I have removed the ground from the modulator's three prong plug with an adapter with no results. I have also removed any copper connection to my cable company, also with no results (this is the culprit 99% of the time in my professional experience with "new" systems). Does any one have any ideas on what could be causing this, and what might solve it?