Digital Radio Technology is powering the conversion from analogue and the deployment of digital radio is moving forward rapidly. Digital Radio Mondiale looks set to transform both the AM and FM bands. DRM is being tested and deployed right across the globe. Digital radio is now available on many platforms or systems and on nearly every broadcast band.

The USA and Japan have developed their own digital radio technology with systems called IBOC and ISDB-T respectively. There are IBOC variants for both the AM and FM bands in both hybrid (analogue and digital signals together) mode and a pure digital mode. IBOC is proving to be a controversial development on the AM bands due to the interference it causes to adjacent channels and via sky waves. It does have a rival called CAM-D but it is a bit of a David and Goliath situation. IBOC has been accepted as the standard for these bands so CAM-D is unlikely to become the dominant technology. Russia new seems to be also developing a local standard called AVIS.

The roll out of digital radio technology started with the Eureka 147 or Digital Audio Broadcasting (DAB) system. DAB was fortunate that clear spectrum was allocated to it in both Band III ( ~ 220 MHz) and in the L-Band (~ 1.5 GHz) so it never had to have a hybrid or simulcasting mode. There has been worldwide deployment of DAB but the broadcasters and regulators have been criticized in the UK for allowing low bit rates to be used to squeeze in as many stations as possible onto a multiplex. The highest bit rate used in the UK is now 192 kbps on BBC Radio 3 whereas 256 kbps is quite common in other countries. OFCOM UK is promoting DAB strongly and the UK will see an expansion of DAB technology before anything else happens. In the short term there will possibly some use of other digital radio technologies such as DRM and maybe even IBOC.

Engineers are busy working on new DRM and DAB standards that could see DRM+ aimed at Band II and DAB-2 providing better quality audio on Band III. It is entirely possible that DAB-1 will become obsolete very quickly given the current trend in Northern Europe where countries are starting to switch off DAB transmitters. Switzerland and Germany are both testing IBOC and many adjoining countries have shown a great interest in the technology.

T-DMB is now gaining ground in Korea, where six multiplex operators have started broadcasting in the capital city, and has been accepted as part of the DAB family that now consists of DAB, DAB-IP and T-DMB. DAB-IP is used on the national commercial multiplex (Digital One). It looks like China may be developing its own version of an integrated digital system while Canada may jump from DAB to IBOC. Many countries are now deciding on their strategy for digital broadcasting: France has recently opted to use DRM on the AM bands and started testing from Villebon in June 2007; India is going to use DRM and DRM+ to replace transmitters up to 108 MHz.

The publication of the DAB-2 standard that uses the commonplace AAC+ audio encoder should make future receiver design a lot simpler as this is the same encoder used by DRM and IBOC. Germany may adopt this standard in the near future.

There are now two multi-standard receivers on the marketplace: the Morphy Richards 27024 and the Himalaya DRM2009. Both receivers have been reviewed and reports are available from HERE.

A Russian receiver manufacturer has also produced a prototype DRM receiver at IFA 2007 but it seems that the manufacturing power of China or Japan is going to be required to produce affordable receivers so that the broadcasters will start producing DRM-only programmes (the reverse of DAB in the UK!)