I have a model B raspberry pi running OpenELEC v4.2.1 connected to my TV using the composite output. I also have a Freeview box receiving terrestrial TV from a coaxial cable connected by Scart lead to the same TV. The Freeview box and Raspberry Pi are at different sides of the TV but are still within three feet of each other. None of the Freeview cables cross over or touch Raspberry Pi cables.
When the Raspberry Pi is turned on the signal on the TV from the Freeview box becomes distorted and eventually ceases. When I turn off the Raspberry Pi the signal returns to full strength. Sometimes the Raspberry Pi will be turned on and the Freeview signal will be good before losing quality without any reason.
What causes this interference and is there any way to shield the Raspberry Pi so it doesn't affect the TV signal quality?