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Modern technology has almost dated the conventional analogue transmission methods involving amplitude or frequency modulation. Although numerous and extensive technical improvements have been made to these analogue systems over the years (high degrees of audio compression, etc.), significant, further improvements are probably no longer possible. The widespread use of digital technology in the audio media – compact discs, and digital cassette recorders – has made ‘CD quality’ the yardstick with which all audio sources are compared. Now, in addition to growing interest in improved sound quality for broadcasting services, an ever increasing number of broadcasting services are being demanded and provided (public and private), and this in turn is leading to increased congestion of the existing broadcasting frequency bands (and thus diminished programme quality). These problems are compounded under mobile reception conditions, for which the VHF/FM was never designed or planned for. The allocation of new frequency bands is a very difficult and time-consuming goal to achieve. Digital transmission techniques, which, when suitably applied, can lead to a more efficient utilisation of the frequency spectrum, provide a means of r