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DRM Plus / DRMplus / DRM+ / Digital Radio Mondiale Plus
Information about the DRM+ system which may provide modern, high quality and flexible digital radio broadcasting.
DRM is designed to operate up to 30MHz, with 5kHz, 9kHz and 10kHz channel spacings covering Long Wave, Medium Wave and Short Wave, coping with fading, multipath and doppler caused by paths propagating via the ionosphere.
DRMplus Mode E is designed for VHF and operates with wider transmission bandwidths, coping with multipath and doppler shift in mobile reception.
Open Digital Radio has some details on DRM/DRM+ here.
ITU Recommendations of Digital System G in January 2012 laid out three specifications for DRM+:
- Systems for terrestrial digital sound broadcasting to vehicular, portable and fixed receivers in the frequency range 30-3,000 MHz
here
- Technical basis for planning of terrestrial digital sound broadcasting in the VHF band here
- Digital radio broadcast service, captioned radio here.
Adoption is not assured; the ITU recommendation of SSB broadcasting for AM radio failed.
In-band Band II DRM+ trials are planned early in 2011 were on the air in Edinburgh, Scotland.
The four month long DRM Plus trials in the UK were radiated from the transmitter site at Craigkelly on the fallow frequency of 107.0 MHz. The official press release is here.
This frequency was previously used by Talk 107 until the licence was handed back to Ofcom. A 28 day RSL by The Coast subsequently operated on the channel in June 2009, when Celador was hoping for an Edinburgh licence.
DRM+ Tests and Trials, including an initial report on the highest power test so far, the UK trial in Edinburgh: 16 February 2011, by Lindsay Cornell, Principal Systems Architect, BBC Technical Committee Chair, DRM Consortium, is here.
A commentary on the above in the US magazine Radio, 2 March 2011, is here.
The DRM+ Experience Day in Scotland press release is here.
A drive-around video of FM and DRM Plus around some beautiful parts of Edinburgh centre is here.
The DRM Consortium report on the results of the Craigkelly, Edinburgh, DRM High Power Field Trial in The United Kingdom is here (32 page PDF).
The BBC January-May 2011 DRMplus tests, at 1kW ERP, showed that a 16-QAM COFDM service, using AAC at 149 kbps (comparable to analogue FM's audio quality), had worse coverage than FM (5kW).
Using more rugged 4-QAM, allowing AAC+ at only 49 kbps (markedly inferior to FM quality), provided coverage that was similar to FM.
Both DRM+ services experienced muting to silence drop-outs of the audio in poor signal areas.
Co-existence with FM services was trialed with DRM Plus occupying a 200kHz FM channel and there was no improvement in the efficiency of spectrum usage.
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Some other trial test transmissions of DRM Plus at VHF.
- NAB, April 2009, Nautel & Fraunhofer: here.
- Paris, 16 July 2009, Band I, 64.5 MHz: here.
- Kaiserslautern, Germany, May 2010, Band III: here.
- Turin, Italy, October 2010, Band I, 55.8 MHz, 40 Watts, 4-QAM, for one year in DRM + from Radio Maria at Villa Gualino, Torre Bert, after previous DRM trials on 26.0 MHz: here.
The ITU Results of the DRM Field Trial in Band I in Turin, Italy are here.
- Sri Lanka, December 2010, Band II: here.
- New Delhi, May 2011, 100.1MHz, 500W ERP, three programme sources: Gold FM, Rainbow FM and AIR News. The DRM+ Showcase full trial with All India Radio and the DRM Consortium showed satisfactory coverage to 23km using the more robust 4-QAM and lower bit rate audio. Higher quality using 16-QAM, needing 7.3dB higher field strength, covered roughly half that radius. The full report is here.
- Simultaneous DRM+ and FM transmissions in FM Band II, on 107.7 and 107.9 MHz respectively, started in November 2011 from Radio Maria in Turin, Italy. Some details and spectral analysis plots are here.
- Vatican Radio, Rome, December 2011, 103.8MHz, 200W ERP, one programme using the multilingual overseas broadcast relay frequency when not in use for FM, here
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- DRM+ The Future of FM, 12 page publicity PDF: here.
- Let us not leave community radio behind in the digital revolution, to the European Commissioner for the Digital Agenda from CMFE, Community Media Forum Europe and AMARC, Association of Community Radio Broadcasters; PDF: here.
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