The Digital Radio Transition

Posted By on Mar 21 2009 12:00 AM
Digital radio is to normal radio what digital television is to your standard analog TV. Digital radio works by turning both sound and data into digital signals at transmission, and then decoding them at the other end using digital radio receivers. The result is CD-quality sound output. And while AM/FM radio quality can suffer from interference caused by signals bouncing off walls, buildings, hills and other structures, digital radio receivers have built-in technology that cleans and filters transmissions, making interference practically non-existent. What's more, with data now able to be sent as part of the signal, digital radio receivers with LCD screens can also give listeners information such as song names, news, weather and more.

Unlike digital television, which can be seen on your existing TV with the addition of a set top box, you'll need a brand new radio to be able to listen to digital transmissions. A digital radio differs from a normal FM or AM one because it has a chip inside that allows it to tune into VHF Band III or LBand.

The United States has opted for a proprietary system called HD Radio(TM) technology, a type of in-band on-channel (IBOC) technology. Transmissions use orthogonal frequency-division multiplexing, a technique which is also used for European terrestrial digital TV broadcast (DVB-T). HD Radio technology was developed and is licensed by iBiquity Digital Corporation.

On 1 December 2005 South Korea launched its T-DMB service which includes both television and radio stations. T-DMB is a derivative of DAB with specifications published by ETSI. More than 110,000 receivers had been sold in one month only in 2005.

In the United Kingdom, the roll-out of digital radio is proceeding since test transmissions were started by the BBC in 1990. The UK currently has the world's biggest digital radio network, with 103 transmitters, with two national DAB ensembles and forty eight local and regional DAB ensembles broadcasting over 250 commercial and 34 BBC radio stations across the UK. In the capital of London there are already more than 51 different digital stations available. In addition to DAB, radio stations are also broadcast on digital television platforms, Digital Radio Mondiale on mediumwave and shortwave frequencies as well as internet radio in the UK. Digital radio ensemble operators and stations need a broadcasting licence from the UK's media regulator Ofcom to broadcast.

Digital radio is now being provided to the developing world. A satellite communications company named WorldSpace is setting up a network of three satellites, including "AfriStar", "AsiaStar", and "AmeriStar", to provide digital audio information services to Africa, Asia, and Latin America. AfriStar and AsiaStar are in orbit. AmeriStar cannot be launched from the United States as Worldspace transmits on the L-band and would interfere with USA military as mentioned above.

Each satellite provides three transmission beams that can support 50 channels each, carrying news, music, entertainment, and education, and including a computer multimedia service. Local, regional, and international broadcasters are working with WorldStar to provide services.

A consortium of broadcasters and equipment manufacturers are also working to bring the benefits of digital broadcasting to the radio spectrum currently used for terrestrial AM radio broadcasts, including international shortwave transmissions. Over seventy broadcasters are now transmitting programs using the new standard, known as Digital Radio Mondiale (DRM), and commercial DRM receivers are available. DRM's system uses the MPEG-4 based standard aacPlus to code the music and CELP or HVXC for speech programs. At present these are priced too high to be affordable by many in the third world, however.

Low-cost DAB radio receivers are now available from various Japanese manufacturers, and WorldSpace has worked with Thomson Broadcast to introduce a village communications center known as a Telekiosk to bring communications services to rural areas. The Telekiosks are self-contained and are available as fixed or mobile units.

Before you rush out to buy a digital radio, be aware that some countries do not have digital radio services or limited digital radio services. Please call your local station or ask around and see if digital radio is avaliable in your country. Below is a rough image of where Digital Radio exists.

Special thanks to Wikipedia, HD Radio

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