In my case I had a ground loop problem once with a satellite feed.

There was no opportunity to use the dual 75 to 300 ohm balun trick because the LNB requires power from the satellite STB. Even if one uses a powered multiswitch, for DirecTV systems, the STB uses different DC voltages to select the LNB polarization. Dish systems use DiSeQ switching control which uses a 20 Khz carrier, which would not pass too well through a balun pair. I used a different trick.

At first, I ran a heavier #6 ground lead from the dish ground rod to the main house grounding point, but this only helped a little.

In my case the loop was between the satellite feed and my subwoofer which had a third prong on the power supply. Rather than break this safety ground to break the loop (potentially very dangerous), I build a little extention cord, terminated in a single gang utility box with a GFCI mounted in it. Thus, I could safely lift the ground, and still have some fault protection via the GFCI. This worled well.

I would not encourage others to do this though, unless they thorougly understand what they're doing: there is a danger of the GFCI not tripping even if there is a short to signal ground, which can travel back on an interconnect shield, possibly causing a fire. It's unlikely, but not a risk that exists with a real ground in place. In my case I consider it about as likely as a "real ground" working itself loose and thus gone, so I accepted the risk.

Another possiblity is to break the loop at the output of your cable STB: use optical digital audio interconnects, and video baluns on the video lines (one, two, or three, for composite, svideo, or component outputs). This won't help digital video signals, though, on DVI or HDMI connectors, unless you use a paid of electrical/optical DVI converters, typically used for long runs. That can get expensive. (Even video baluns can run several hundred dollars each, for good ones).