Edited my own post. I found the OTA scanning option on the menu. After scanning, I do get two new subs for channels that I already received (50-1 and 50-2, for example). But the scan shows 90+ signal strength for many other stations that don't actually come in when I try to tune them in. I currently get no PBS stations at all, even though the scanning routine shows them at over 90 signal strength.
Any ideas what might be at fault here? I live right in DC, just about a mile from the transmitters for these stations, according to antennaweb.org. I should be getting every OTA station known to man (ok, small exaggeration, but you get the point...)
Thanks for your thoughts.