If you're using RCA jacks (Yellow = video, red & white = audio) you won't get HD at all with that setup. You either have to use HDMI or Component cables. Component would be Red, Green, Blue for Video and Red/White for Audio.
I use direct tv with my Samsung 56" TV and when I first got it I would flipped from discovery in SD to discovery in HD and the difference was night and day. Now I have my SD duplicate channels turned off.
I would still hook up rabbit ears to your TV for comparison purposes. If the over the air channels look better than the cable HD channels at least you can show the cable tech the problem.
I use direct tv with my Samsung 56" TV and when I first got it I would flipped from discovery in SD to discovery in HD and the difference was night and day. Now I have my SD duplicate channels turned off.
I would still hook up rabbit ears to your TV for comparison purposes. If the over the air channels look better than the cable HD channels at least you can show the cable tech the problem.