CSpan HD channel

I cannot view CSpan HD channel 1128 in zip 37027.  It is in my guide.  It is very poor reception on every tv and they are on cable boxes.  Many chats and Comcast people have not resolved it.  

When I record it, I see most of it when I play the recording.  However when Rep Lofgren says lets play a video, then sometimes a still is on the screen while the person's voice recording plays.

I finally figured out how to play the SD channels and can watch channel 7 the next time.

If anyone can figure out how to fix my problem, please reply.  I can see CSpan 2 and 3 HD.