HD poor quality

I don't understand why offer HD local channels when they are not working most of the time.  I've been having this issue since I ordered cox a few months ago, and its frustrating in trying to watch a channel that pixelates a lot and I am forced to watch in standard  format.  I have compared the HD local channels with my digital antenna TV and I get better reception out of my HD antenna, then with the cable box.  Cox can instruct me to make an appointment for a technician to visit my home and try to repair the issue, but having a technical background, I know for a fact that the issue is not locally at my home, but its the transmission from the cox station to my cable box.  I haven't had cable TV for a while, but I believe that the extra cost of the TV service (low since I already have internet with them) is not worth the frustration I am having.

In a spirit of a last effort I would like someone from Cox to explain to me why am I (I'm sure I'm not the only customer) having so poor quality of local HD channels.