Digital Radio Technology is powering the conversion from analogue and the deployment of digital radio is moving forward sometimes at a very slow pace. Digital Radio Mondiale looked set to transform both the AM and FM bands but international broadcasters have been dropping the technology mainly due to their budgets being slashed. In Europe DRM is most likely to be used in Russia, the Ukraine and possibly Spain although the BBC is a member of the DRM Steering Board. 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 did 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 fading away.
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. It is unlikely that any other digital radio technologies such as DRM or IBOC will be used in the UK.
Engineers have developed new DRM and DAB standards that sees DRM+ aimed at Band II and DAB+ providing better quality audio on Band III.
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. Russia has also indicated that DRM/DRM+ is going to be used extensively throughout this vast region.
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 three multi-standard receivers on the marketplace: the Technisat Multyradio, the Morphy Richards 27024 and the Himalaya DRM2009. Apart from the Himalaya availability of the others is limited. A company called Uniwave produced a few Chinese manufactured DRM capable radios with a large viewing screen that displayed the Journaline application. The receiver never went into mass production.