TV Antenna ??

I put my tv in today. The roof antenna worked fine with the booster on. The signal was weak but better than I expected. I live so far from a tv station that an antenna is usually usless. When I turned on the power roof vent it interfered with the picture. TV was running on ac power. Anyone else ever had this problem or is it because of a weak signal? Also when I hooked up the sat.dish I couldn't get a signal on the tv. I had the dish hooked to the ext. tv outlet. I took it off the outside connector and ran it directly to the tv and it did fine. Is there some sort of switch I missed or is it a bad inside tv power receptacle?