[Decolliber]

I have a Directv satellite dish (older round one) with two outputs (= dual LNB??) feeding two receivers in different rooms. I want to add a third DVR (Tivo) receiver in another third room. Can I simply buy the DVR receiver and put a splitter on one of the original two lines to feed a signal to the new third receiver? Or do I need to either replace the old dish with a new triple LNB dish or add a second dish to feed a signal to the new 3rd DVR receiver?
I cannot find the answer to this question at the DirecTV web site. Sent them an email but no reply. I went to my local Best Buy and two very young salesmen each gave me different answers: one said yes you can use a splitter to get a signal to the 3rd receiver and one said no you can't. They sell the stuff and don't even know how it works. I just did a Google search on how sateliite TV works but could not find an answer.
Any Directv/satellite TV experts in Pelicanland?