Originally Posted by douflag
... our 6-7 yr old HDTV didn't display any pictures despite picking up the channels.
This is a confusing statement. Could you please clarify it?
As for whether or not your TV is receiving local OTA broadcast TV stations or cable programming, this is an easy one. In all probability, your new TV identifies each programming source. If you receive a digital broadcast, then your TV will likely display the call letters or other identifying information about each subchannel. If your programming comes via cable, then it is likely that your TV will explicitly list "CABLE" with the channel number.
Press the [info] button on the TV's remote control and read what appears on your TV screen.