that allows you to split several coax sources (i.e. cable, antenna) into a box and from that box a composite cable to the TV? I have a dish receiver split into the master bedroom to a wall mounted TV. Since there is no box (Dish splits 2 from 1 box)I have coax providing the signal to the TV. Since the TV accepts OTA HD. I would like to run an antenna off the coax to get access to those channels. See my dilemma?