A ground loop in your AV system caused by antenna connection or TV cable is very common if you have your computer connected to the same system. This type of ground loop problem can be solved by using suitable isolator between your AV system and the antenna cable.
Antenna isolator is very convient way to solve antenna connection related ground loop problems. Unfortuantely isolator has some drawbacks: attenuation and possible poor suscpectibility to RF interference.
Here is the picture of one commercial antenna isolator:
The circuit inside main details pretty much resembles the simple circuit shown at Building your own antenna isolators page with some RF filter added to the center:
Another type of antenna signal isolator is RF transformer based antenna isolator as shown at Building your own antenna isolators page: