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- Digital Radio Mondiale (DRM) background -
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Background

 

As DRM is intended as a replacement for AM (Amplitude Modulation) the existing channel spacing, medium and long wave 9 kHz and 10 kHz for short wave, is maintained. Audiences for AM radio have declined, and most people will relate to the poor audio quality of AM music.

 

Also 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 transmit 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’ as the principals of AM would be familiar to all the radio pioneers.

 

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, electronic programme guide, programme text, and automatic tuning to alternative frequencies make DRM receivers easier to operate. DRM can also transmit multimedia pages and data.

 

If you listen to a DRM broadcast 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.

 

DRM background
COFDM
FAC
SFN
MSC
SDC data 1
Multimedia
Bandplan
DRM future
DRM audio
FAC sync
DRM multiplex
DRM modes
SDC data 2