TECHNICAL LIBRARY

 

AN OVERVIEW OF   DRM TECHNOLOGY 

                                                                                                        - RAMESH GHARDE

DY.DIRECTOR GENERAL (ENGG)

Introduction:

The existing analogue AM Broadcasting system has inherent problem of interference and noise moreover transmitters are operated on very high power which involves high operational cost.  Moreover audio quality is very poor due to poor S/N ratio.  To overcome all these inherent problems a digital Broadcasting System has been developed named as Digital Radio Mondiale. Mondiale is a French word means “ World Wide “.  The DRM Technology is set to revolutionize radio broadcasting on the long, medium short wave bands. 

Evolution of DRM Technology:

The DRM consortium was formed in 1998, where a small group of pioneer broadcasters and manufacturers joined to create a universal digital system for AM Broadcasting below 30MHz.  The DRM is open standardized digital broadcasting system.  Unlike any other digital broadcasting system which are proprietary in nature.   DRM operates on broadcasting frequency up to 240MHz including AM Bands (LW, MW, SW) and VHF band I & II (FM BandI & Band II). The broadcasting frequencies are basically divided in accordance with their propagation characteristics:

L W (Long Wave)                            :  30 KHz………300 KHz

MW (Medium Wave)                    :  300 KHz……..3 MHz

SW (Short Wave)                           :  3 MHz……..30 MHz

VHF                                                    : 30 MHz……..300MHz

UHF                                                    : 300 MHz……3 GHz

VHF is split up into three bands

            VHF I                                                  : 47MHz…….85 MHz

            VHF II                                                 : 87.5 MHz….108 MHz

            VHF III                                               : 174 MHz…..230 MHz

UHF is split up into two bands

            UHF IV                                               : 470 MHz…..606MHz

            UHF V                                                : 606 MHz…..826 MHz

DRM on short, medium and long wave for broadcasting upto 30MHz called DRM 30.  The DRM 30 Broadcasting system provide large coverage and low power consumption.

             DRM Broadcasting above 30 MHz is called DRM + which uses the same audio coding, data services, multiplexing and signaling scheme as DRM 30 but introduces advance transmission mode optimized  for those bands.

 

Salient features of DRM.

1)    DRM system has been designed to allow suitable analogue Transmitter to be modified to switch easily between analogue and digital broadcasting.  This will save initial cost.

2)    It is possible to simultaneously transmit more than one signal carrying the same program in both analogue and digital mode using same antenna system which is called Simulcast.

3)    DRM uses In Band on Channel (IBOC) technology which enable to transmit in hybrid ‘Mode’ i.e. Analogue & digital mode. This is also called HD Radio (High Definition Radio).

4)    Main service channel (MSC) may be upto four services any one of which can be audio or data.

5)    Single & multi frequency network synchronized operation.

6)    It supports Text messaging , advance text information for weather, sports and news, slide shows, EPG (Electronic Program Guide) and similar value added services.

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