I have a Mitsubishi WS-55807 using Direct TV HDTV (RCA HDTV Digital Receiveer model - DTC 100). I do not think I am getting HDTV. My TV supports 480i, 480p, 960i and 1080i, but the picture is not HDTV on the HD channels. Can anyone shed some light on this for me? My receiver is set at 1080i. Thanks