The connection is HDMI, I had the connection in HDMI 1/ Act, I has moved the connection to HDMI 2 that is also a 1080 input, the picture quality has improved but not to the as good as the aerial signal.
I'm sorry to learn about the problems you're experiencing with your TV picture at the moment, I've not been able to accurately locate your account to take a look at the set top box from our end unfortunately.
So I'm able to take a closer look, could you respond to the private message I've sent with the requested information? You can view the message by clicking the purple envelope on the top right of this page.
Have you been able to try another HDMI cable at all? Or another HD device (like a DVD player) using the same cable and HDMI port on your TV? To eliminate the cable and the TV as a potential cause of these picture issues.