The small dish services such as Dish Network and DirecTV use circular polarity instead of linear polarity to send their signals down. This allows for, among other things, the use of a smaller dish (18 inches). Unfortunately, there's not much free on those services, just a few channels such as the Muzak audio, NASA-TV, GOL-TV (soccer), and a few banner channels.
Most of the satellites we are picking up in FTA are linear polarity, and the signals are not meant for reception by people in their homes. They are usually uplinked for cable companies, broadcasters, news services, etc., and as such require a larger dish. The Channel Master dish you have will work very well, if it is in good condition. It probably already has a linear LNB on it.
By the way, the only difference between an LNB and LNBF is that the LNBF has a built-in feedhorn as part of the unit (like the DirecTV and Dish Network dishes have), whereas the LNB has a separate feedhorn that it is attached to. The Channel Master you have is most likely an example of a dish with a separate LNB and feedhorn (as opposed to an LNBF)...