I live in the Washington-Baltimore region and I have an AM21 that works well with an HR24-500. The OTA signal comes from an antenna in my attic, and after the initial setup on the HR24, the "Edit Off-Air Channels" listing shows 41 channels. All of the channels have a white "x" next to them, and almost all of them show up in the DirecTV program guide. The two that do not appear in the program guide are channels 4.1 and 4.2 (WRC-TV out of Washington, D.C.) The HR24 signal meter shows both these stations are getting 100% signal strength. I'm aware that the DirecTV OTA channel database is finicky, but these channels are clearly in the DirecTV database, otherwise they would not be showing up in the Edit Off-Air Channels listing after the initial setup. And, like I said, both channels test with a strong signal. But no matter what I have tried, those two channels will not appear in the program guide, meaning that I cannot tune them in. I've rebooted several times, and re-run the initial setup three or four times, trying slightly different zip codes in my area as the primary and secondary. But always the same result: the Edit Off-Air Channels listing shows 41 channels found, but only 39 appear in the program guide. And the two that are missing are always channels 4.1 and 4.2. Everything else is working fine and dandy with the AM21 and the OTA channels. I would like to figure out why I cannot see channels 4.1 and 4.2 in the program guide after the AM21 has clearly scanned them successfully. Thanks in advance for any help.