The issue here is that most basic 12 Volt Fans use brushes, these brushes generally emit Electrical RF noise.

To make sure it is RF noise coming down the Antenna cable – change the TV source to DVD, HDMI or something else and if the signal and sound are fine this means that the Noise is being transmitted by RF at the TV frequency. This also means that the Fan could not meeting CE or RF regulations.

There are only a few solutions:

1.      Change the Fan to a brushless fan these are much quieter electrically.

2.      Move the Antenna and cabling as far away as possible from the Fan.

a.      This is not always easy in RV’s and Boats.

3.      Try earthing the Antenna Shield to the same ground as the Fan Motor via a capacitor.           

a.      This will be a trial an error process as different fans will have different frequencies.