Says unusable signal when trying to hookup my...

Question

I am trying to play my nintendo 64 so i hooked it up using the antenna/cable port. The game will flip on the screen for about 1 sec and then the screen is blue and it says unusable signal at the bottom of the screen. It says the same thing when i first hook up my PS3 but it always starts working. Also the Nintendo 64 works on all the other tvs in our house.