There is a menu you can get to that allows you to select the satellite, frequency, and polarization. On our system, it was one of the unlabeled buttons near the bottom-end of the
remote control.
As I understand it, FTA is usually MPEG-2, so the box would have to be able to decode MPEG-2, and know to NOT attempt to decrypt the signal.
But please correct me if I'm wrong, as I know very little about this.