The BBC first launched FM broadcasts in 1955, but FM didn’t really hit the public consciousness until 1988 when BBC Radio One launched it’s FM service. The advantages at the time were the clear sound (compared to AM) and the possibility of stereo. AM had also suffered during the night with interference from distant stations, which FM was immune to. The development of FM didn’t bring any significant increase in choice until regulators introduced a requirement for FM and AM services to be different.
DAB Digital Radio
DAB was developed through the nineties, and the BBC had about 60% coverage for their services by 1998 when the first commercial licence was awarded to Digital One. DAB is broadcast in blocks called “multiplexes”, each of which carries multiple services. One multiplex takes up roughly the same air space as one FM station. By 2003, Digital One were covering 85% of the UK with their multiplex which carries services such as Virgin, Classic FM and digital-only services like OneWord. Between 2000 and 2004, 35 local and regional licences were awarded for areas across the UK. This meant that most places in most places in the UK you could receive both national multiplexes, one regional multiplex and at least one local multiplex. This adds up to around 35 different stations.
This increase in choice is the biggest advantage of DAB over FM. Other advantages include the fact that multiplexes can run on a single frequency, no matter how big their coverage areas are. That means that if you’re listening to a national service in one end of the country, and drive to the other, your radio never has to switch frequencies. BBC Radio 4, for example, has around 50 distinct FM frequencies, most of which are reused in different places. On DAB it has one, which it shares with 10 others.
There are other advantages to having everything on a single frequency – it means that if there are particular “black spots” where the signal is weak, broadcasters can add a new transmitter on the same frequency.
DAB still uses radio waves, so it can be received in much the same way as FM. DAB receivers are nearly all the same forms as FM receivers – in-car, personal, portable, “boom box”, hi-fi, mini systems and even PC peripherals.
As well as the audio, DAB offers data. All DAB radios can show you the name of the station you’re tuned to, and nearly all of them can show you some extra text from the radio station. This can contain information about the song that’s playing, the current programme, what’s coming up next, contact details – virtually anything the broadcaster wants to say and listeners want to know. There are other data services being broadcast for which receivers are not yet on the market. One example is an Electronic Programme Guide, which lets you look through the schedule at what programmes are coming up in the future and even mark them to be recorded. The first radios to make use of this data are expected in early 2005.