Ken, note that strictly speaking "RCA" is the connecting plug, not the cable. Nevertheless, cables are often referred to that way, and especially so when the cable isn't of 75 ohms impedance. So, it would be good to know whether an "RCA cable" being considered is of 75 ohms impedance or not. If it isn't, there would be some impedance mismatch in video use which would limit the length of the run(and make it unacceptable at more than a few feet for HDTV bandwidth). For 15', the cable would probably be okay for standard TV regardless of its impedance, but 75ohm cables are available at such low cost from sources noted here such as Monoprice and Triangle Cables that you might as well get a cable with a good impedance match.
