I'd like to get HD air broadcast but I've only got standard cable and on the back of the hdtv, there's only one "antenna in". What do I do? Buy a digital antenna (any recommendations?), get a two-way splitter? I read in the manual under managing channels I can switch antennas via remote control but I don't get what kind of setup this is referring to. With cable plugged in, I can switch to air but it's not HD.