"A large number of digital TV channels can be viewed on a Sky Digibox without a Sky subscription or a viewing card, as the signal is not encrypted - see Sky's Free to Air channel list. Over 200 TV and radio channels are available, including the BBC channels, some of the news channels, and most of the shopping channels and radio stations.
If you have an old Sky box and a satellite dish, you should be able to watch these free-to-air channels. For a list of the free channels that can be viewed on a Sky dish and decoder without subscription, see Sky's Free TV channel list.
A small number of channels are available "Free-to-view", which means they can be viewed on a Sky box for free, but they require a viewing card. These are the Channel 4 and Five channels. Sky used to supply cards originally known as Solus Cards, as part of Sky Freesat. If you need a card, but don't want to take out a subscription, give Sky a call and ask for a Sky Freesat viewing card."
http://www.radioandtelly.co.uk/satellitefree.html#fta