Except for in rare exceptions you wont be using the DN equipment for anything reguarding true FTA. You will need a larger dish and an lnb that is capable of rx'ing linear polarization. DN, DTV etc broadcast in an incompatable circular polarity. The larger dish [anywhere from 30" to 4 ft] for Ku band is because the linear tx'ing FTA signals are generally lower in power. C band dishes are on the order of 6 ft to 10 ft or more, but avarage 7-8 ft for decent signal receiption. I have a VS Plat. It is a very good box for both C and Ku band.
HD FTA is another animal altogether. Some of the many HD gurus we have on the board may jump in and fill in the blanks there. I would say, if you possess computer skills, and a high end 3gig+ dual core pc, you may look into a DVB setup for HD. It can be done PCI or via an external USB unit. It is NOT plug and play, but is the most user configurable once you learn the ropes.
One thing more to pass along. Asking about DN equipment associated with non DN [aka FTA] recievers, implys you could be asking about the illegal sect of sat hobbiest. That is a taboo subject here and will get you 'escorted off the premises' if intentional or persistant. If you want to get into the free and legal aspect of the hobby this is the place. It is a plethoria [hey it's almost Thanksgiving, when else do you get to say that word?.........lol] of knowledge and skill here. No question is dumb, no RTFM responses. Try to do some research so you can know what questions you need to ask.
gl