DRM for Shortwave – the Tipping Point


Author: Dr. Simon G. Keens, Sales and Business Development Manager – Ampegon Power Electronics AG, Baden, Switzerland

After the Digital Radio Mondiale consortium’s years of effort raising public awareness of DRM radio’s next-generation capabilities, it’s encouraging to see increasing interest in DRM. With over 2.5 million in-car DRM receivers in India – increasing every day – and governments around the world working to introduce regulatory legislation to permit digital DRM transmissions, there’s a feeling that DRM may soon reach the tipping point where it rolls with its own momentum.

Our expertise is shortwave transmissions, which will arguably experience the greatest improvement in broadcast quality of all DRM frequency bands. Traditionally known for long-distance broadcasting, analogue shortwave maintains a stubborn reputation for being incapable of stereo sound, subject to atmospheric distortion and fading, and representing the broadcast technique of last resort for distant, isolated audiences. DRM shortwave, however, represents a 21st century step-change in technology; a fact that is gradually becoming evident to more and more broadcasters around the world. The recent Brazilian DRM shortwave trials heard throughout the western hemisphere, and Radio Marti’s broadcasts into Latin and Central America, seem to confirm this.

This groundswell was recently highlighted by Voice of America, who carried a short video report1 on the opportunities offered by DRM shortwave. This raised two apparent issues which we often encounter: that updating shortwave transmitter infrastructure is too difficult and expensive, and that DRM can never fly properly while affordable receivers are not available.

To address the first issue, we must highlight the difference between a “high power” shortwave transmitter and “high power” FM transmitters. High power shortwave means output powers up to 2MWp, whereas a similarly named (and short-range by comparison) FM transmitter only produces a minor fraction of that power. Such “high powers” are necessary for the intercontinental range of shortwave transmitters. The whole of India, with its 1.4 billion citizens can be covered from three centrally located shortwave stations. Surely then, it cannot surprise anyone that shortwave transmitters are somewhat more expensive. Then consider that with DRM, shortwave transmissions can achieve stereo FM-like quality, with 2-3 channels per frequency and digital error-correction preventing the ‘traditional’ fading and atmospheric distortion. You don’t even have to retune receivers between day and night frequencies anymore!

Currently individual high-power transmitters start at approximately one million dollars. ($1.2M), including fully DRM operation, which we feel represents excellent value for national (if not international or intercontinental!) coverage for decades to come. Lower power solid-state shortwave technology is also now adding another strategic dimension: A 25kW solid-state DRM shortwave transmitter can accompany an existing 100kW analogue transmitter to provide similar coverage footprints. This is possible since the threshold for “good” reception by a standard analogue SW receiver antenna is generally agreed to be >42dBu field strength. However, thanks to DRM’s error correction, field strengths of >30dBu are sufficient for uninterrupted reception in glorious FM-like quality! This, of course, means a smaller transmitter can cover the same area with a digital service, while the existing high-power continues to broadcast analogue. Solid-state transmitters are significantly cheaper than their higher power cousins and expected to become cheaper still as 65V LDMOS technology becomes widely available in the market, and multiple orders permit bulk-buy savings.

And if existing shortwave transmitters are not older than 15 years or so, they are more likely to be upgradeable to most-modern standards to facilitate DRM operation. Currently, Ampegon is working with customers to upgrade significant numbers of higher power transmitters to DRM capabilities at a relatively modest cost. Depending upon complexity, transmitter upgrades can (according to our best estimations) be achieved for less than 20% of the cost of a new transmitter! Considering that in DRM mode, a shortwave transmitter’s electricity consumption can be reduced by around 60%, investments are repaid in only a few years, in addition to significantly improving the broadcaster’s environmental credentials. Reducing 60% of 715kW* continuous electricity consumption means millions of dollars of savings surprisingly quickly!

The second point is the enduring question: “What’s the point of broadcasting DRM when nobody can buy/afford receivers?” Unfortunately, this does not account for the latest information from chipset developers and receiver manufacturers: A number of manufacturers, including Gospell, Starwaves, and others, now offer a range of low-cost receivers and after-market vehicle upgrades, available today at modest cost if serious quantities are ordered. Cambridge Consultants announced2 that their DRM reference receiver could cost less than US$10 (with rumours persisting that the final figure might be as low as $8 depending on volumes).

As with everything in the world of business, judgement of cost and value is relative. Shortwave transmitters ARE relatively expensive compared to FM transmitters, but their reception footprints are barely comparable, and their role in broadcasting isn’t the same; so why should their price be? Similarly, spending a hundred-thousand dollars or more on upgrades may be intimidating, but compared to 60% savings on a three-hundred-thousand-dollar electricity bill*, it is clearly the economical long-term choice. And sure, DRM receivers do cost a lot when buying them one-by-one, initially, while R&D costs are being recuperated; but buy enough for an entire country and the price will immediately drop dramatically.

The technology is ready, the regulations are coming into place, and now there is simply a choice: to embrace a digital future with DRM providing better service at lower cost, or to ignore it simply because it is different? We are convinced that people won’t simply stop listening to radio, and we remain ready to support the transition to the digital future however we can.

1: Digital radio powering global communications

2: Digital radio for the world – the newest old news?

[* Consider a 500kW transmitter, 70% electrical/RF efficiency, (optimistic) USD 0.10/kWh energy cost, in operation 50% of the time (4380h/yr)]

Author: Dr. Simon G. Keens, Sales and Business Development Manager
Ampegon Power Electronics AG, Baden, Switzerland