You cannot have a normal splitter between the receiver and the dish, but from the receiver to the TV is not a problem.
I have a dome (Winegard on this coach and KVH on last one) and also have a Dish LNB on my sat internet dish. The two cables come into an A/B switch, the cheap Radio Shack one, then one cable to receiver. I usually use the dome but there are times when one is blocked and the other isn't. I've had this set up for about 8 years on 2 different coaches with out a problem. Sometimes I have to run check switch when I go from one to the other but there are also times I even get away not doing that depending on the channels I watch.