If your heaters have a BLOWER/FAN it could also be a possible fan motor brushes (if it uses them) might be causing RFI interference with the high def digital TV reception. I had a similar incident using a ceiling mounted exhaust fan in my bathroom causing the bedroom TV to freeze its picture then go to the dreaded 'NO SIGNAL' blue screen. I would turn-off the bathroom fan and all would clear up instantly.
I have this same symptoms happen when turning on some of my newly installed LED lights a few years back until I changed them out for NON-REGULATED type LED Boards.
The new digital TV modes are very sensitive to things like this it seems...
Roy Ken
