Radio broadcasting spent most of the twentieth century as an analogue medium. The signal was a continuous wave — amplitude-modulated in AM, frequency-modulated in FM — and it reached listeners the same way it had since the 1920s. The move to digital was not a single event but a decades-long process that is still unfinished in many parts of the world.
Why Digital?
The case for digital broadcasting rested on several technical advantages. Digital signals are either received clearly or not received at all — there is no gradual fading, hiss, or multipath distortion of the kind that affects FM reception in urban environments. Digital multiplexing allows multiple programme channels to share a single broadcast frequency, dramatically increasing the number of stations available without additional spectrum. And digital systems can carry supplementary data: song titles, programme information, programme guides, emergency alerts.
DAB and the European Path
Digital Audio Broadcasting — DAB — was developed in Europe in the late 1980s and launched commercially in the UK in 1995. The UK became one of the world’s most advanced DAB markets, eventually reaching a point where digital listening (across DAB, internet, and smart speakers) overtook FM listening in weekly reach. Norway completed a full switch-off of its FM national networks in 2017, becoming the first country in the world to do so. Switzerland followed later. Germany and several other European nations have set or are considering digital switchover dates.
HD Radio in the United States
The US took a different path. Rather than developing a wholly separate digital band, HD Radio technology allows digital audio to be transmitted alongside the existing analogue signal on the same FM or AM frequency — a system called in-band on-channel (IBOC). A compatible receiver picks up the digital signal for improved quality; an ordinary receiver falls back to the analogue signal. The transition has been slower and less complete than in Europe, with HD Radio penetration remaining modest compared to the scale of the US broadcast market.
What Got Left Behind
Digital transitions do not erase analogue overnight. Millions of analogue receivers are still in use, and in many countries analogue FM continues to serve the majority of listeners. The cost of replacing every car radio and kitchen set in a country is enormous, and regulators have generally moved cautiously. Even where digital switch-overs have occurred, localised analogue services often persist for communities with poor digital coverage.
The Internet as a Parallel Track
While broadcasters debated DAB versus FM, internet streaming quietly became a major listening platform in its own right. Listeners accessing stations through apps, smart speakers, and browsers now outnumber those using DAB in some markets. This changes the strategic landscape considerably: the argument for building new transmitter infrastructure weakens when a phone and a data connection deliver better audio to more places than any terrestrial transmitter network.
The analogue-to-digital transition in radio has never followed a neat script. The result is a patchwork of technologies — FM, DAB, HD Radio, internet streaming — that coexist in different proportions depending on where in the world you are listening.