I came across an interesting news report recently about an Digital Radio Mondiale (DRM) test that is currently taking place on 86.5 MHz in Copenhagen, the capital of Denmark.
While several countries have DAB systems up and running, some are carrying out test in or around Band 2 (88-108 MHz) and seeing if digital DRM signals could co-exist with analogue FM signals.
The DRM test in Copenhagen started on the 13th of October 2021 and runs until the 1st of August 2022. There is an option of extending this to the 30th of August 2023.
This is a collaborative project organised by Open Channel, an independent Danish network operator in Copenhagen, with Canadian Nautel (transmitter), German RFmondial (DRM modulator & measuring instruments) & Fraunhofer IIS (Content server) and Swedish Progira (network planning).
The project is supported by Gospell, NXP, partners in Denmark and other non-DRM Consortium members like Bauer Media (supplying content) and Kathrein (antenna).
The frequency allocated is 86.5 MHz and with a bandwidth of 200 kHz, which makes room for two DRM signals. Each DRM signal has a capacity of 186.4 kbps (16QAM, CR 5/8) and accommodates three audio channels and multimedia services, so for the 200 kHz a total of six digital radio stations can thus be broadcast. Further down the line there are ambitions to involve the Öresund region (commonly known in English as the Sound, a strait which forms the Danish–Swedish border) and possibly collaborate with another FM station on the Swedish side.
The height of the antenna is 88m and the terrain elevation is 8m (more details below). In phase 1, Open Channel will test single DRM channel with 120 Watt ERP. The coverage probability for mobile reception in Greater Copenhagen is illustrated in the picture below...
The trial on the 86.5 MHz frequency has also been approved by the Swedish Post and Telecom Agency. The fact that the experiment is done a bit below the regular FM band (band II 87.5-108 MHz) is due to the fact that there is no space in this dense region. The new receivers for FM/DRM can handle 64-108 MHz.
“We are working on expanding the FM band in Denmark from 85 – 87.5 MHz, so that the Danish FM band goes from 85 to 108 MHz and thereby create more space to introduce digital radio on the FM band”... says Kenneth Wenzel, project manager and director of Open Channel.
“This DRM field trial offers a unique opportunity to showcase the versatility of DRM-FM by packing two DRM signals within a single FM channel allocation demonstrating optimal spectral efficiency for DRM using a Nautel VS transmitter.”... says Philipp Schmid, CTO at Nautel.
Source... https://www.drm.org/drm-for-fm-in-the-heart-of-europe/
I hope that the DRM tests in Copenhagen are successful and that the system could become widespread like vhf-fm has. DRM seems to be in the doldrums at present and certainly using Band 3 frequencies would have a lot of mobile coverage problems.
ReplyDeleteAnother mode of transmission was tried some decades ago - single side-band with supressed carrier ( -6dB I think ). I only heard it from HCJB , Ecuador on shortwave. It depended on the receiver extracting the carrier so that it could be re-introduced as normal AM demodulation.
I often wonder why stereo AM could not have been achieved by separate sideband modulation of an AM carrier , ie USB for left-hand channel , and LSB for right-hand channel and compatible with ordinary AM. Tight bandwidths required of course .