What is the yellow video jack for on the back of satelite systems for? The coax cable brings in the signal to satelite, then from there to the TV. I have A/V jacks that go from the satelite receiver to the main receiver and then a video jack going from the main receiver to the TV, but if I disconnect the coax going to the TV I lose the picture. So what purpose does the Video jack serve, is it just to enhance the picture? Thanks.