M DT81 DIGITAL RADIO TUNER Arcam DAB Tuner Figure 1.1 A digital radio tuner (courtesy Arcam) 2 Newnes Guide to Radio and Communications Technology MOKIA Figure 1.2 An example of a mobile phone handset (courtesy Nokia) many countries in the world around 60 to 70 per cent of the population own one of these phones. The enormous usage has enabled a consider- able amount of development to be undertaken. The first phones that were used were very large. Now phones can be slipped into a shirt pocket, and all the time the level of functionality they offer is increasing. The first generation systems used analogue technology. The second generation systems use digital technology, and now the third generation systems (3G) are offering high data rate capabilities that will enable them to provide far more facilities and flexibility. Radio is being used increasingly in many short range 'wireless' applications. Not only are many items such as remote very low power short-range devices including door bells, thermostats and the like being widely used these days, but standards like Bluetooth, HomeRF and 802.11 are being developed and equipment introduced for interconnecting computer devices, mobile phones, and many devices around the home. This is likely to fuel an enormous growth in the short-range radio market as it will mean that offices and the home will use radio instead of wires. Radio is also used for long-range communications. Satellite technology has enabled radio communications to reliably span the world. Once the short wave bands were used, but even though there are many uses for these frequencies most of the communications we use today are routed An introduction to radio 3 via satellites to give communications worldwide. Satellites are used for many purposes. Obviously they enable long-distance communications to be made, but they are also used in applications that include weather monitoring, navigation, search and rescue, direct broadcasting and much more. Naturally there are many other areas where radio is used today, fr