DRM+ is an expansion of the existing DRM standards with regard to the useful frequency range. DRM+ therefore must likewise be able to digitize VHF sound broadcasting. Digital radio mondiale (DRM) was developed as a digital sound broadcasting standard for worldwide use in long wave (LW), medium wave (MW) and short wave (SW). DRM is used for sound broadcasting as well as to transmit additional digital data for frequencies up to 30 MHz.
The frequencies required are exposed to highly fluctuating propagation conditions. In this frequency range, the waves are influenced by the ionosphere, and they are reflected depending on the time of day, season, and relative number of sunspots. In this frequency range, primarily AM has previously been used for sound broadcasting. Thanks to the digital standard, the AAC+ audio coding and the COFDM technology, signal transmission now promises outstanding quality as compared to conventional AM broadcasting.