I do that now. One split goes to my TiVoHD with cable cards. My channels via that path are mapped to the 800's. CBS/4 HD is 804 ABC/5 HD is 805 etc...... My split that goes directly to the TV (Vizio) receives the signals like this: CBS/4 HD is 4-1 ABC/5 HD is 5-1 Fox/25 HD is 25-1 etc...... What I am not sure of is if one were to subscribe to a digital, say starter pack, where you normally would not receive HD, I don't know what happens. It is possible that they would have to install a filter/trap to keep you from receiving things you are not supposed to get. I am receiving now exactly what I am supposed to receive. Nothing more. Nothing less.