US President Donald Trump at the weekend signed an executive order cutting funding to Voice of America. Founded in 1942, VoA – whose future is now uncertain – uses shortwave radio to broadcast current affairs programming to millions of listeners across the world.

Shortwave radio – where the wavelengths of the signal being broadcast are between 10m and 80m – was an important technology between the 1960s and the 1990s. However, its significance diminished as digital media platforms, especially the internet, became ubiquitous.

Shortwave radio’s significance was largely due to its ability to be broadcast over extremely long distances. Signals bounce off charged particles in the ionosphere, allowing them to travel to the far side of the planet without the need for hundreds of transmitters. This is why shortwave broadcasts have played an important role in the dissemination of information during wartime.

A rebirth of the technology may now be taking place – with a digital twist.

“In South Africa, we have never used shortwave even though it gives you the ability to transmit over long distances,” said Mark Willams, a broadcasting industry veteran and presenter at LM Radio. No local broadcasters used shortwave, but that didn’t stop South Africans from tuning in to international broadcasts, including VoA, the BBC World Service and Radio France Internationale.

“Shortwave (and medium wave) radio is expensive to transmit, and the technology took a back seat to FM because of FM’s superior quality. Later, new broadcast media such as the internet also took precedence.”

Shortwave radio signals (3-30MHz) are highly susceptible to interference from power adapters, fluorescent or LED light sources, internet modems, routers and computers. The higher frequencies (88-108MHz) used for FM radio do not pick up much of this interference.

Antiquated

According to Williams, South Africa’s FM transmission infrastructure is well developed, with signal distribution towers across the country. But these broadcasts are based on antiquated analogue technology. Although this setup was state of the art decades ago, South Africa has fallen behind as the rest of the world moved on to digital radio.

The major cost factor for analogue broadcasting is that the frequencies used to transmit FM channels only travel around 60km, meaning many more broadcast towers are needed, costing money to deploy and maintain. The towers must also have line of sight of each other, meaning they must be grouped together, with greater density required in hilly territory such as in Kwa-Zulu Natal.

Read: Device transmits radio waves with almost no power

Shortwave transmissions, on the other hand, allow for towers to be fewer and further between. When digitised, they also required far less power to propagate.

This where shortwave broadcasting is set to make something of a comeback, according to Williams. Advancements in broadcasting technology have made it possible to “refarm” the spectrum in the shortwave bands. Digital shortwave radio has the advantages of its analogue predecessor, such as long-distance signal propagation and low power consumption, without its drawbacks.

Whatever happened to shortwave radio? Digital shortwave radio is also known as Digital Radio Mondiale (DRM), a which is designed to work within the bands currently used for analogue radio broadcasting, including shortwave.

DRM signals are less susceptible to interference and offer more channels for the same amount of bandwidth, meaning three channels can exist where only one could before, but with stereo sound quality.

There is another standard, called DRM+, that uses FM frequencies – and other, similar frequencies – for digital broadcasts.

DRM is not the only digital radio broadcasting standard around. DAB, or Digital Audio Broadcasting, is competitor to DRM that has been deployed across much of Europe as well as Australia. Nearly 30 European countries have DAB or DAB+ radio broadcasts. Like DRM, DAB allows more stations to be broadcast using the same bandwidth as analogue broadcasts.

One of the drawbacks of migrating to digital radio, whether using the DRM or DAB standards, is that listeners must buy radios that can decode the digital signals. According to Williams, this is already happening in other parts of the world like India where DRM adoption is on the rise. He said car manufactures are now shipping DRM-capable vehicles into India. Accessories like USB sticks and other adapters that add DRM functionality to traditional radios are also available.

Read: 100 years of radio in South Africa – and still going strong

“For Africa, DRM is the answer. We have large areas to cover where there are small population groups in those areas, and DRM is cheaper. Radio technology in South Africa hasn’t changed all that much in the last 30 years. Radio has been stuck in a rut and frequencies are limited, but that is not the case anymore, there are lots of frequencies and lots of channels available,” said Williams. — (c) 2025 NewsCentral Media

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