Actually all coax wires from all rooms are coming to a central wiring panel but I am not going through any distribution module, etc. Last night, I did a little test where I used F-connector-to-RCA adapter to both ends of a 6ft coax cable and used that to connect DVR's composite monitor output to a TV's RCA input. It worked fine, so I confirmed that I can use coax to carry composite video.
Then, I connected same F-connector-to-RCA adapters to the coax cable going to a room on 2nd floor (about 40-50ft length) and hooked up to DVR's monitor out and same TV, no signal !
I believe coax is fine because I tried sending Dish Network signal over it and it works fine. Could length be an issue?