It's my understanding that you need to keep a satellite dish connected in order for the OTA receivers to work. With the 6000 it was reported that you lost the OTA when rain fade happened. This is a dangerous situation, for the cloud that's causing the rain fade might be severe weather heading your way. Only OTA can deliver your local forcast. Hopefully they built-in some fudge factor on the 921 that allows continuous OTA reception if the dish signal drops out. Fortunately for me, I see 3 orbital locations 119, 110, and 61.5. When I do experience rain fade, it is usually from only one or two orbital locations. 61.5 is southeast while the other two are southwest. The only other issue is snow fade. Again usually only one dish is covered to the point where reception is affected.