Reduce noice from cable hookup in HT system?

I had the same problem.Purchased power conditioners and filters. But later I found the cable ground( the co ax cable is grounded when enters the house) is broken by the lawn maintainence personal.
Please check that.
See that the cables are not running parallel to each other. I used a filter for 6 dollars called as Hum bucker for cable TV.Purchased from virtual dynamics.
Now there is no noise.

You could do a search on ground loop for a cheap radio shack solution, but I don't know how the digital cable would react to that. I use the monster cable power conditioners such as the HTS1000/2000/2500 and have had very good luck with them. I have used the mondial magic but it did not do anything for my system because I had improperly grounded cable and the mondial instructions state that it is for "properly grounded" cable systems. I liked the monster because i only had to connect the cable to it, none of the other components needed to be connected for the gound to be broken, and you can find them inexpensivly on ebay for $80+.