The DRM consortium has published the results of DRM FM trials done earlier this year in New Delhi and Jaipur. The results are encouraging.
The measurements showed that DRM could deliver a healthy range of audio services in the given spectrum (up to three audio and one multimedia service per DRM signal block) while allowing maximum utilisation of the FM-band spectrum. Every DRM signal occupied only 96 kHz spectrum bandwidth — half the bandwidth analogue FM requires for a single audio service.
According to the consortium, the trials confirmed that adding DRM transmissions to the FM band is fully compatible and does not interfere with ongoing analogue FM services. Also, DRM reports that it managed to broadcast multiple signals side-by-side from a single transmitter (multi-DRM transmitter configuration) and operate in flexible configurations alongside an analogue FM signal from the same transmitter (simulcast transmitter configuration).
In addition, DRM explains that the tests successfully delivered a Journaline advanced text service in multiple Indian languages. This is important to provide Emergency Warning Functionality (EWF with CAP interface) and enable traffic, travel, and online teaching services over broadcast — essential for those without Internet connectivity.
DRM services came through on different consumer receivers, including car radios and mobile phones. This showed that existing receiver models, already supporting DRM in the AM bands, as adopted by India, can support DRM in all bands by a simple firmware upgrade without hardware modifications.
Finally, DRM adds that the trial also confirmed that DRM is fully compliant with the regulator’s (TRAI) recommendations and existing analogue FM spectrum licensing.