The first reaction to this subject is to ask why should anyone want to broadcast radio programmes from a satellite, and why should the broadcasts be digital? Digital broadcasting is an evolving technology which will provide an enhanced variety and choice of programme, and a rugged delivery mechanism. These are the main driving forces in broadcasting at the moment. Although the advantages of digital broadcasting were identified many years ago, there are at the time of writing very few all-digital transmissions. The reason for the limited availability is that the combination of technical theory and production technology is only just starting to produce products which can compete in the marketplace. 4 Satellite broadcasting has gained a place in the market already. Satellite tele vision is available in many places, with a wide choice of programmes. On the other hand, there is very little satellite sound broadcasting. Again, it appears to be a matter that is dominated by the needs of the market. Satellite television provides a useful product, whereas satellite radio is not yet offering something which people feel that they must have. To understand why, we need to under stand what it is that people expect from radio.