DRM - Digital Radio Mondiale
Advantages of DRM:
- Clear, static-free sound.
- Scrolling text on the radio screen. Option to broadcast in stereo. Embed text files within the program - teaching notes, explanations, documents, pdf, long Bible passages. Include still images or slides to expand the audio presentation. Broadcast two or three different programs simultaneously on the same frequency, selectable by the listener. Uses only 44% of the transmitter power to accomplish the same coverage.
The Digital Radio Mondiale (DRM) broadcasting system has been designed by broadcasters, for broadcasters, with the active assistance and participation of both transmitter and receiver manufacturers and other interested parties (such as regulatory bodies).
DRM is an open standard, meaning that its system description is openly published allowing all manufacturers and interested parties to have free access to the complete technical specifications and can design and manufacture equipment on an equitable basis without any need to pay for a license to the DRM Consortium. This has proved to be an important mechanism for ensuring the timely introduction of new systems to the market and for accelerating the rate at which equipment prices are reduced. This is a significant consideration for broadcasters investing in DRM infrastructure, manufacturers investing in receiver development and production, and even more for the listeners who will need to invest in the new DRM-capable receivers.
For the DRM technology there is no per-use fee, annual payments, or similar – neither for broadcasters/network operators, nor for broadcast or receiver equipment manufacturers. The DRM Consortium is not involved in managing or receiving any IPR royalty for DRM products. Rather, royalties need to be paid directly to the individual IPR holders, unless they are already taken care of by a product component supplier (e.g. for a DRM receiver module). For further information on IPR, please click here: ipr.drm.org.
DRM is the only global digital radio broadcast standard that embraces all the currently used radio frequency bands. It has been designed specifically as a high-quality digital replacement for all former analogue radio broadcasting in the AM and FM/VHF bands; as such it can be operated with the same channeling and spectrum allocations as currently employed. An overview of the frequency-bands where DRM operates is shown in the Figure below:
For the physical transmission, the DRM standard describes several different operating modes (i.e. modulation parameter sets), which may be broadly split into two groups:
• For DRM transmissions below 30 MHz there are four different robustness modes which allow the DRM signal to be tailored for the AM broadcast bands with their very diverse propagation characteristics enabling regional up to international service coverage
• A dedicated robust mode, which is centered above 30 MHz on the FM broadcast band and optimized for transmissions in the VHF bands, can be used for local to regional service coverage.
DRM has received the necessary recommendations from the ITU, hence providing international regulatory support for transmissions to take place. The main DRM standard has been published by ETSI. In addition, ETSI publishes and is the repository of the entire range of current DRM technical standards.
The introduction of DRM services allows a broadcaster to provide listeners with significant improvements in service reliability, audio quality and, most importantly, usability. The standard provides many features and facilities that are impossible to replicate in analogue broadcasting. It is essential that prospective broadcasters understand the potential and flexibility of the system to allow them to optimize and configure their DRM networks in accordance with their own market conditions.
The key features of DRM and the package of benefits are described in detail in dedicated section of our website.
The DRM Consortium
The DRM Consortium (Digital Radio Mondiale) is an international not-for-profit organization composed of broadcasters, network providers, transmitter and receiver manufacturers, universities, broadcasting unions and research Institutes. Its aim is to support and spread a digital broadcasting system suitable for use in all the frequency bands up to and including VHF Band III. There are currently some 100 members and supporters from countries around the world, active within the Consortium.
DRM was formed in Guangzhou, China in 1997, initially with the objective of “digitizing” the AM broadcast bands up to 30MHz (long, medium and short-wave). The DRM System Specification for broadcasting below 30MHz (”DRM in AM”) was first published by ETSI in 2001. A few years later, the decision was taken to extend the use of the standard to the VHF bands (Band I, Band II and Band III).DRM in the bands above 30MHz ensures that the standard has the same multiplex and signaling scheme, the same OFDM design (with new parameters) and the same audio codecs.
DRM Transmissions below 30 MHz
The DRM standard used in the AM bands (also referred to as DRM30) can deliver FM-comparable sound quality and is specifically designed to utilize the broadcast bands below 30MHz (Long Wave, Medium Wave and Short Wave) which allow for very-long-distance signal propagation.
DRM in AM bands is designed to fit in with the existing AM broadcast band plan, based on signals of 9 kHz or10 kHz bandwidth. It also has modes requiring only 4.5 kHz or 5 kHz bandwidth, and modes that can take advantage of wider bandwidths – 18 kHz or 20 kHz – allowing DRM to operate alongside AM transmissions in every market of the world.
The system allows the new digital transmissions to co-exist with the current analogue broadcasts, and a significant amount of work has been undertaken to quantify the operating parameters that assure mutual analogue and digital compatibility. Hence the changeover from analogue to digital broadcasting can be phased over a period of time, which in turn allows existing broadcasters to spread the required investment to meet any budgetary constraints. Furthermore, unlike some other digital systems, the DRM system has been designed to allow suitable analogue transmitters to be modified to switch easily between digital and analogue broadcasts. This can significantly reduce the initial investment cost for a broadcaster. An additional budgetary benefit is the reduction of the cost of transmission.
For a complete description of DRM in the AM bands please refer to the DRM Handbook.
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Broadcast Equipment
Ampegon produces two distinct ranges of transmitters: lower power solid state-transmitters and higher power tube transmitters.
Tube transmitters are available with 100kW, 300kW or 500kW maximum power ratings, while the solid-state range is modular with power outputs between 1.5kW and 25kW.
Broadcast transmitters can be supplied alone, or along with a range of broadcast auxiliaries, necessary for remote control and monitoring, and test loads.