DAB digital radio was developed by a consortium of 12 partners, known as EUREKA-147 - the system was originally called Digital Audio Broadcasting (DAB) and this is still used to distinguish a true DAB receiver from all other radio receivers.
In 1994, Eureka-147 was adopted as a world standard and, today, most of the world has either implemented the standard or is currently testing it. The exceptions are the United States, which has embraced both satellite digital radio and High Definition radio, and Japan where cable is the chosen method of delivery for new radio formats.
For background and technical details on the Eureka 147 standard, go to www.worlddab.org
What is a multiplex?
Digital radio is made up of a single block of frequencies called a multiplex. The multiplex is able to carry stereo and mono radio channels as well as services such as text and data. The UK has been allocated seven multiplexes by Ofcom in the spectrum 217.5-230.0 MHz. It is possible to carry more services on one frequency allowing the spectrum to be used more efficiently. This spectrum is called Band III in the UK.
Some countries also use Band III for DAB broadcasts, but others already use Band III for analogue television and so the higher frequencies in what is called the L Band, from 1228MHz to 1575 Hz are used for DAB digital radio. These frequencies are also used by services broadcast from satellites. DAB digital radio in Germany uses both Band III and L Band, while Canada uses only L Band.
So, if you buy a receiver in the UK it will be designed to pick up DAB signals on Band III and may not work some other countries. In the future, dual band receivers will be available for use anywhere.
In the UK, L Band is currently used for fixed point to point communications, but in 2007 it is expected that L Band frequencies will become available for DAB in this country.
What you can't do
Like analogue radio, DAB digital radio operates via a series of terrestrial transmitters, thus there are national, regional and local multiplexes broadcasting to prescribed areas of the country. This means that, as with analogue radio, you will receive only those stations within your transmission area. Unlike satellite radio, you cannot receive local stations from, say, Wales, if you are in Scotland. Unlike internet radio, you cannot receive international stations. Nor can you take your DAB radio abroad and receive UK stations on the beach at Marbella!
In the UK, both national commercial and BBC DAB digital radio reaches more than 85% of the population. This is set to rise over the next two to three years as Ofcom rolls out a further tranche of DAB multiplexes around the country.
Aerials
Because analogue and DAB are two completely different broadcast techniques, an FM aerial will not work for digital radio.
A digital radio comes with an indoor aerial which should work perfectly well unless you are in a steel framed building or perhaps a basement. As a rule of thumb, if you have poor FM or mobile phone reception, you may not receive DAB through an indoor aerial.
If this is the case, you may need a roof mounted aerial. To obtain the best results, either use a dipole or a Yagi aerial which must be pointed at the transmitter. DAB aerials must be vertically polarised.
For more technical information on aerials contact the DAB Aerial Helpline on: 0800 542 8265.
For more information on DAB in-car aerials, click here