The earth connection of the grounding block for the CATV Coax cable shield is causing the problem.There is a difference of potential, voltage, between the CATV earth ground and the main electrical grounding system of your home.
Buy one of these and install it between the incoming CATV cable coax and the cable box.
You also could try cleaning and re-terminating the ground wire on the grounding block. The grounding block should be located on the outside of your house where the cable company's coax cable connects to the outside of the house. Sometimes the block is inside a box, sometimes just exposed on the outside of the house.
Clean both ends of the ground wire and re-terminate.
The other end of the ground wire from the grounding block should connect to the main grounding system of your home. Not a separate ground rod only. A separate isolated ground rod connection will cause a ground loop condition as well as a lightning hazard for your audio and TV equipment.
Buy one of these and install it between the incoming CATV cable coax and the cable box.
You also could try cleaning and re-terminating the ground wire on the grounding block. The grounding block should be located on the outside of your house where the cable company's coax cable connects to the outside of the house. Sometimes the block is inside a box, sometimes just exposed on the outside of the house.
Clean both ends of the ground wire and re-terminate.
The other end of the ground wire from the grounding block should connect to the main grounding system of your home. Not a separate ground rod only. A separate isolated ground rod connection will cause a ground loop condition as well as a lightning hazard for your audio and TV equipment.