tv interference

Tighten all your cable connections.

Also make sure all your ground connections are solid.

There are many devices that can cause TVI (Television Interference) or RFI (radio Frequency Interference)

LED lights are noted
If your TV is running on batteries even standard lights (Lower the voltage) can do it.

Fans.. Some have burshless motors (no interference) others brushes (interference).

BOOK.. ARRL.ORG click on the store link look for Radio Frequency Interference.. I think they have a few books on the subject. I used to have one of them (ARRL's own) and it was very comnprehensive since it was written by people who actually know what they are dealing with.

Yes there's both 12v power supply filters and A/V noise filters that go inline on your coax. I suspect you can get both over the counter at say Radio Shack.