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Thursday, 4 December, 1997, 14:32 GMT
MEDIA ANALYSIS: Digital shortwave - the future of international broadcasting?
The ban which the Democratic Republic of Congo imposed for three days this week on local FM relays of the BBC, Radio France Internationale and the Voice of America highlights the potential risk for international stations of their growing reliance on local rebroadcasting to achieve better reception abroad. To retain a global reach whilst improving audibility, international broadcasters are now turning to digital technology for shortwave. Successful tests of parallel digital and analogue SW broadcasts have already taken place and more developments are expected soon. Morand Fachot, of BBC Monitoring's Foreign Media Unit, has more details:

The Democratic Republic of Congo's short-lived ban on relays of the BBC, Radio France Internationale and the Voice of America by local FM radio stations shows once again how international broadcasting is still seen as a potential threat by politicians in many countries.

The main incentives for tuning to foreign broadcasts have always been a lack of comprehensive news in the local media and/or the poor quality of these.

Kinshasa's ban - imposed on Sunday, and lifted on Wednesday - was a reminder to global broadcasters who have sought to improve reception of their programmes and boost their audiences by concluding hundreds of FM and MW rebroadcasting agreements throughout the world in recent years.

International broadcasters have traditionally relied on amplitude modulation to broadcast on frequencies below 30 Megahertz [MHz], and mainly on shortwave (SW), to transmit their programmes.

Shortwave, and to a lesser extent mediumwave and even longwave, is attractive to international broadcasters and listeners alike, because:

For listeners, receivers are relatively cheap and easy to operate.

For broadcasters, the initial investment in transmitters and antennas is quite substantial, but it enables them to reach huge numbers of listeners in many countries over a long period.

Reception on these frequencies, particularly on shortwave, generally suffers from rather poor audio quality, which is a major factor in the continuous decline in their popularity.

Local FM rebroadcasting was thus seen as an attractive solution to ensure the future of international broadcasting. However, the potential risks of local rebroadcasts being switched off by hostile "gatekeepers", or simply replaced by a growing number of local stations in need of frequencies, were not lost on international broadcasters.

Together with the need to improve audio quality, they were major incentives in their search for a long-term solution combining the advantages of both shortwave - global reach - and FM - high-quality audio.

Digital technology was seen as offering a solution to this problem as it offers superior audio thanks to compression. Broadcasters, transmitter and receiver manufacturers have now embarked on a programme to use digital modulation (DM) for shortwave, also known as digital SW.

In late 1996 the European Eureka Project 1559, Narrow Band Digital Broadcasting, was launched. A worldwide consortium, Digital Radio Mondiale (DRM), was formed to decide world standards. DRM meetings have so far defined certain guidelines aimed at ensuring the gradual introduction and viability of DM shortwave, and the future extension of DM to mediumwave and longwave:

  • existing transmitters and antennas should be able to transmit both AM and DM broadcasts with only minor modifications;
  • parallel AM and DM broadcasting (simulcast) is needed to ensure reception on both future DM receivers and current analogue receivers, hundreds of millions of which will still be in service for the foreseeable future;
  • - DM will allow multimedia broadcasting, with data and even pictures being transmitted alongside audio;
  • DM should have a much better audio quality than AM;
  • it should be also less susceptible to interference and more reliable;
  • DM receivers should be very user-friendly and relatively low-priced.

For broadcasters, DM, when fully introduced, should allow significant savings as it requires far less power than AM to deliver a better signal to the same target area.

Two DM systems have already carried successful full-scale simulcast tests in Europe: Thomcast Skywave 2000 in France, and T2M (Telekom-Telefunken-Multicast) in Germany.

With the introduction of DRM announced for February 1998, the adoption of digital modulation standards is set to pave the way for the industry to start developing receivers. The progress of this new technology might reverse the fortunes of shortwave and of international broadcasting.

BBC Monitoring (http://www.monitor.bbc.co.uk), based in Caversham in southern England, selects and translates information from radio, television, press, news agencies and the Internet from 150 countries in more than 70 languages.

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