Just replaced my 721 with a 622, but didn't want the HD package (for now), so left original dish: superdish for 119/110/105 & original switch: DP34. Connected the new 622 (in single mode) to one of the cables (that used to feed the 721) with the DP separator provided in the box. seemed to work fine, but when I tried using 2nd tuner (like PIP & swap), it says error in switch - run check switch. I do & it says input 1 sees 3 sat's but has reception error & input 2 only sees one sat. When I direct connect the 622 with both original feed cables & no separator, it works fine. Also have a 522 & did some testing with it with similar results. Do separators go bad mid-stream, or is it a compatibility issue, or something else?? thanks for any help...John