Hey all. I just bought a new house that was prewired for home theater. The subwoofer output is coaxial cable. I bought 2 F-Coax to F-RCA wallplates but for some reason my sub doesn't power on when my receiver turns on. It's an older Onkyo HTIAB powered sub. The room is pretty big and it makes me wonder of the signal is too weak for the sub to respond to it. Going directly into the receiver, the sub works fine. I guess it could also be a bad connection somewhere in the wall. Is there a way to test the coax connection? Thanks

Anyone? :D

When you say 'coax connection' are you talking about the wallplate or the cable ?
Do you own an ohmmeter ,or multi-meter ?
If so, measure for continuity in the cable/s and the wallplate connector.
I don't understand why you need the wallplate.
Are the receiver and sub in different rooms ?
John

There is a wallplate on the wall behind the receiver and the cable goes to a different wall in the back of the room. The cable is coaxial. I needed the wallplate to adapt the coax to RCA.

Ok.....
Do you have an ohmmeter?
You need to take resistance readings. You most likely have a loose connection in the wallplate.
Remove the wallplate from the wall and make sure the cable connection is tight.
Verify continuity between the wallplates. Sometimes the coax cable connection loosens(backs-off). Tighten with an open-end wrench. If its what I think it is!

An easy way to check for continuity is at one end use a piece of aluminum foil to connect the center wire to the outside wire of the coax. Then, use an ohmmeter and see if it records a resistance at the other end between the center and outer wire. (What you're doing is creating a big loop going from the inside to the outside wire using the whole length.) If the connections are female, then use male-male cables to create a male ending connection, as it's easier to use the foil and ohmmeter on male connections. The resistance will probably be between 1 and 10 ohms (I believe my house coax wiring is about 6-7 ohms).