Digital shortwave broadcasting provides great audio quality. All you need is some open-source software to decode the data into audio.
Most days, listeners in North America and elsewhere can tune in to FM-quality radio on shortwave. The technology is called DRM or Digital Radio Mondiale. DRM is one of four competing technologies in the effort to shift traditional AM broadcasting to digital. Most European countries have adopted Digital Audio Broadcasting, or DAB. In Europe, use of digital receivers is edging above 50% of households. In the United States, it’s HD Radio, which has the added benefit of simulcasting traditional and digital signals. More than 75% of US stations are using this, but listener adoption, not so much – around 2%. Analog still rules the waves. Japan is implementing yet another format.
A few countries and shortwave broadcasters have adopted DRM. These include India, Brazil and Indonesia. India, in particular, is in the process of shifting its medium and shortwave services to digital. You can view a schedule of DRM shortwave broadcasts to find one available by time of day or target region.
All of these technologies use a codec to digitize and compress audio, which is then sent over a multi-carrier ODFM transmitter. This means stations are split into sub-carriers which are frequency multiplexed across the channel. In some cases, listeners can receive several different programs on one channel.
Digital Shortwave Broadcasting – Dream Software
I often listen to DRM from Radio Kuwait on 13,650 kHz. Here is a recently posted demonstration video of what Kuwait sounds like using digital. Digital radio is either perfect or nothing, no in-between.
The easiest way to tune in digital shortwave DRM is to use the open-source Dream software receiver. Using Dream assumes you are able to get a signal of at least 10 kHz bandwidth out of your receiver. To decode DRM, you need a signal with a 15 dB signal to noise ratio. If you can get 13-15 dB SNR on the digital signal, it will decode audio with 50 dB SNR – perfect. For decoding, you can either stream audio or I/Q data from your receiver to the Dream software.
The challenge is finding the AAC codec for playing the audio. It is proprietary. You need to either download an earlier version of Dream which included the codec, or find one elsewhere.