edVirtus Reference

What Is Digital Radio Mondiale (DRM)?

How Does Digital Radio Mondiale Improve AM and Shortwave Broadcasting?

Digital Radio Mondiale (DRM) is an international digital radio broadcasting standard developed to replace or complement conventional analogue AM broadcasting in the long-wave, medium-wave, shortwave, and VHF frequency bands. It provides significantly improved audio quality, greater resistance to interference, and the ability to transmit digital data services alongside conventional radio programming while using existing broadcast spectrum efficiently.

The basic principle is straightforward. Instead of transmitting an analogue audio waveform, DRM converts audio into a compressed digital data stream. The data is protected using forward error correction (FEC) coding and transmitted using orthogonal frequency division multiplexing (OFDM), which divides the signal among many closely spaced subcarriers. This combination provides excellent resistance to fading, multipath propagation, and interference, particularly on challenging HF and shortwave radio paths.

A useful analogy is sending a written message instead of speaking over a noisy telephone line. If parts of the spoken message are lost, understanding becomes difficult. A written message, however, can often be reconstructed even if a few words are damaged or missing. Similarly, DRM uses digital coding and error correction to recover information that would be severely degraded in an analogue transmission.

DRM supports a wide range of operating frequencies. DRM30 operates below 30 MHz, covering the long-wave, medium-wave, and shortwave broadcast bands, while DRM+ extends the standard into the VHF bands up to approximately 300 MHz. Depending on the operating mode and channel bandwidth, DRM can provide near-FM-quality audio on bands that traditionally carried analogue AM broadcasts.

In addition to high-quality audio, DRM supports a variety of digital services. These include programme information, multilingual text, emergency warning messages, electronic programme guides, journaline text services, images, and other data applications. Because these services are integrated into the digital transmission, broadcasters can provide much richer information than is possible with conventional analogue broadcasting.

It is important to distinguish Digital Radio Mondiale from DAB (Digital Audio Broadcasting). DAB was designed primarily for VHF broadcasting using new spectrum allocations, whereas DRM was specifically developed to operate within existing AM broadcasting channels, allowing many existing transmitters and frequency allocations to be reused with relatively modest modifications. This makes DRM particularly attractive for international shortwave broadcasting and countries with extensive AM broadcasting infrastructure.

Today, Digital Radio Mondiale is used for national and international broadcasting, emergency information services, and long-distance radio coverage in many parts of the world. Although its adoption varies between countries, DRM provides broadcasters with a practical path from analogue to digital transmission while preserving the wide-area coverage characteristics of the traditional AM broadcast bands. It remains one of the principal international standards for digital radio broadcasting below 300 MHz.