This question has come up numerous times. Here is a copy of my solution which I have posted before:
I had this same problem. Here are the two parts you need, total cost $11:
http://www.radioshack.com/product/index.jsp?productId=2103063&cp=&kw=300+ohm&kwCatId=2032057&parentPage=search
http://www.radioshack.com/product/index.jsp?productId=2062059&cp=&pg=1&kw=ohm&kwCatId=2032057&parentPage=search
Connect the cable coax wire to the transformer/splitter.
Connect the wires from the transformer/splitter to the 75-ohm coax combiner/splitter.
Connect the 75-ohm coax combiner/spltter to the input on your TV.
This was done for me by the cable TV guy. Worked like a charm. Why? I don't know. I guess it breaks the ground loop.
I had this same problem. Here are the two parts you need, total cost $11:
http://www.radioshack.com/product/index.jsp?productId=2103063&cp=&kw=300+ohm&kwCatId=2032057&parentPage=search
http://www.radioshack.com/product/index.jsp?productId=2062059&cp=&pg=1&kw=ohm&kwCatId=2032057&parentPage=search
Connect the cable coax wire to the transformer/splitter.
Connect the wires from the transformer/splitter to the 75-ohm coax combiner/splitter.
Connect the 75-ohm coax combiner/spltter to the input on your TV.
This was done for me by the cable TV guy. Worked like a charm. Why? I don't know. I guess it breaks the ground loop.