I've been in touch with Light Coder as I tried to perform his requested experiment. I found that 8-bit recording in HDSDR somehow creates a DC spike that isn't present when recording 16-bit. After I told him, Light Coder asked in an email if I would send him an ATSC recording to help him debug HDSDR, and since people had asked for ATSC before, I figured I might as well make a blog post out of it. So here's a screenshot and the download:
This is the first ATSC signal I encountered while scanning with the rabbit ears, and I believe it's PBS.
atsc_rfchannel_33.7z (660 MiB)