DRM background

The Digital Radio Mondiale (DRM) consortium was founded in 1998 representing broadcasters, academic institutions, and manufacturers. Its purpose is to develop a non-proprietary technical standard for the replacement of analogue AM (Amplitude Modulation) radio with digital radio, also called DRM. [Mondiale is the French word for world].

Not to be confused with the other DRM acronym -
Digital Rights Management.

International Telecommunications Union (ITU), International Electrotechnical Committee (IEC), and the European Telecommunications Standardisation Institute (ETSI) have all approved DRM broadcasts for frequencies below 30 MHz.

As a replacement for AM the existing channel spacing, medium and long wave 9 kHz and 10 kHz for short wave, is maintained. On medium wave a DRM radio broadcast can provide close to FM audio quality - most people will relate to the poor audio quality of AM music. With DRM the audio quality is primarily determined by the broadcast mode and spectrum occupancy (i.e. radio bandwidth of the DRM signal).

Don’t confuse the terms spectrum occupancy and audio bandwidth as meaning the same thing - with DRM they are not directly related, unlike AM.

If you listen to a DRM signal on an ordinary short-wave AM radio then all you will hear is noise. There is no discernible modulation pattern when listening to DRM using a AM demodulator.

AM is inefficient in terms of spectrum usage as it requires twice the bandwidth to transmit audio as the same audio information is contained in both side bands. It is also inefficient in terms of transmitter power as 50% of the broadcast power goes into the carrier. It is not necessary to have the carrier although this complicates the receiver design slightly. Radio amateurs gave up using AM many decades ago and use Single Side Band (SSB) or more accurately Single Side Band - Suppressed Carrier. Radio amateurs sometimes refer to AM as ‘Ancient Modulation’.

When receiving DRM any audio deterioration due to radio propagation fading or interference is not so evident compared to AM. Providing the DRM decoder software receives enough digital data correctly then it will be able to accurately rebuild the audio or data as it was originally coded at the transmitter.

Also the display of the name of the radio station, programme text, and automatic tuning to alternative frequencies will make DRM receivers easier to operate. DRM can also transmit multimedia html pages and data.