You can delete the diplexer and OTA to the Orby receiver. Just connect your satellite cable direct to the Orby receiver, but if you do that, of course your OTA channels aren't going to work through your Orby receiver, and consequently, you won't have access to the program guide and "favorites" function of the receiver for your OTA channels.
I don't use the Orby antenna, but I have an OTA antenna on a rotator, and still use the diplexer to feed those OTA sigs through the diplexer into the Orby receiver so I can use the receiver functions and have the OTA channels included in my list.