Analogue broadcasting

Radio stations transmit via radio frequency electromagnetic waves. Radio waves are part of the electromagnetic spectrum that also includes light and heat and is used to provide many services in our day to day lives, including television, radio and mobile phones.

In analogue broadcasting (eg AM and FM) speech and music is used to directly affect, modulate, characteristics of the radio signal. These changes are then interpreted by the receiver back into speech and music. Any interference is unable to be distinguished from the intended program.

Digital broadcasting first converts, encodes, the speech and music into a series of digital numbers plotted against time. This digital bit stream is used to modulate the radio signal. Error protection systems can then be used so that even if interference occurs in reception the intended numbers can be restored. Ergo, better reception.

Ancillary services

A supplementary service provided as part of a digital radio broadcast. For example an Electronic Programme Guide (EPG) or track listings.

Digital broadcasting

A way of broadcasting television and radio where pictures and sounds are encoded into 'computerised data’ or bits for storage, broadcast, and transmission. See also ‘Analogue Broadcasting’.

DMB

Digital Multimedia Broadcasting (DMB) is based on the Eureka 147 standard and is used to broadcast multimedia content to mobile devices. This already includes the provision of web content and electronic programme guides in the UK and elsewhere.

DRM

Digital Radio Mondiale (DRM) is a set of digital audio broadcasting technologies designed to work over many bands, including bands currently used for AM broadcasts, particularly shortwave. DRM is one technology platform being explored for the rollout of digital radio in regional, rural and remote Australia. A DRM test was conducted in Canberra during May 2007.

The DRM consortium formed in March 1998 when a small group of broadcasters and manufacturers joined forces to create a universal, digital system for the broadcasting bands below 30 MHz. By contrast to DAB, The DRM system maintains the traditional one to one relationship of broadcaster to transmitter.

Ensemble

See multiplex.

EPG

Electronic Programme Guides (EPGs) are commonplace in pay and digital television systems. The screen on digital radios will allow a similar radio programme guide to be displayed.

Eureka 147

Eureka 147 is a technology standard for digital radio that was developed by a consortium of European broadcasters and manufacturers in the 1990s. Eureka 147 has been widely accepted across the world as a standard for digital radio, with the USA and Japan pursuing different technologies.

FM flutter or multi-path distortion

Most people are used to many interfering sounds when listening to AM. Even though FM is somewhat more immune to many types of interference it does sometimes suffer a nasty edginess and ‘thwack-thwack-thwack’ distorted sound.

This is usually caused by reception of multiple signals. The direct main signal together with other signals slightly delayed in time after being reflected off tall buildings and/or terrain. DAB digital radio does away with this type of distortion.

Multiplex

Part of the transmission infrastructure for digital radio. A multiplex combines several audio channels and combines them into a single stream. Data and other services – such as multimedia content – can then be added to form an ‘ensemble’.

Each multiplex has a gross data capacity of 1536 kbps. At typical error protection settings, the net data capacity is assumed to be 1152 kbps.

Programme Associated Data

PAD for short. See ancillary services.

Simulcast

A digital broadcast that is identical to existing analogue programming is known as a simulcast.

WorldDAB

WorldDAB is an international, non-governmental organisation whose role is to promote the awareness, adoption and implementation of Eureka 147 based technologies worldwide. It is now known as WorldDMB.