DAB hand

Is everyone aware of digital radio? It started up only a few weeks ago and for once, Perth was first DAB off the wank, if you’ll pardon the expression.

In case you don’t know, we’ve had AM (Amplitude Modulation) radio since the early 1920s and it’s that crackly, static prone ‘wireless’ that we all grew up with. The thunderstorm to the north at this moment is putting its lightning flash crackles into my speakers.

Then in 1978 (or thereabouts) we finally got FM (Frequency Modulation) radio, decades after the rest of the civilised world. Did you ever notice how clear and static free the sound from TV was, compared to radio, especially out in the country? That’s because TV sound was always FM. It’s inherently pretty immune to interference and has wider bandwidth, hence it sounds better. We had FM TV sound from the start of TV in 1956, but it took another 20 years before the paternalistic governments of the day thought we were mature enough for FM radio. “No demand”, they said. Yeah, no demand because most people had no idea it was available.

Anyway, that led to stations like 96FM, which if you remember, dominated the Perth music scene in the 80s. It also allowed the ABC to start ABC Classical FM on 97.7MHz, still the only source of serious music in Perth, unless you count the ABC and SBS radio channels on digital TV.

Which leads to the next point: if you like listening to classical music, even FM is not completely noise and distortion free. It’s way better than AM, but is prone to noise (hiss) because of its wider bandwidth (15KHz), and multipath distortion. This is exactly the same as ghosting on TV, a second image displaced from the main one due to reflections from buildings or aircraft or whatever. You need just as good an antenna system for FM radio as you do for TV, and pointed at the transmitter.

Cut to the 1990s and Britain and Europe developed digital TV (DVB, for Digital Video Broadcasting) which is the system we adopted. Britain, meanwhile, also developed DAB, digital radio, which after nearly two decades of delays, we’ve finally got, albeit in a modified form called DAB+.

What are the benefits? Stereo for one. But the main benefit is the same thing that makes digital TV (DVB) so clear and free of ghosting and interference – it’s digital. It’s transmitted as ones and zeros which are coded and interleaved with error correction. Once decoded in the receiver, you have an exact replica of what was transmitted, despite noise, electrical interference, multipath, etc etc. You also have a wider bandwidth, as wide as CDs (20KHz), lower distortion and a signal to noise ratio of 96dB, as for CDs.

But more, you also have the capability, in fact it’s inherent in the design of the system, for multiple channels from the same station’s signal. That means the ABC can broadcast ABC Classical, for instance, plus other music or speech channels on the same signal, just as they can with digital TV. Have you noticed ABC1, ABC2, ABC3, ABC Kids, ABC Jazz all coming from your set top box?

But wait, there’s more! Being a digital signal and with memory being so cheap now, some digital radios will let you record the program in the radio, rewind it, and play it again if you want.

And more! The station can also send text and images along with the music, so that you no longer need wonder what’s playing, you can look at the display on the radio and see, 6IX – Rolling Stones, Route 66, 1963 for example. They’re not doing that yet, but we live in hope.

Which leads to the final point: when we plebs were finally deemed sufficiently mature enough for FM radio in 1978, we were only allowed three stations to start with: ABC-FM, 96FM and what’s now called RTR-FM, the University volunteer station. Established AM stations weren’t allowed to change to FM.

Then, in their wisdom, the government placed ethnic foreign language and talk stations on FM. No doubt they appealed to some, but using the hi-fi band to broadcast talk never made sense to me.

Eventually in the early 1990s, tenders were called for new FM licenses, but existing AM stations had to bid for licenses. That meant only well heeled proprieters could afford the move and my favourite station, 6IX, missed out.

So for the past 15 years or more, we’ve had to put up with noisy, distorted, muffled AM if we wanted to listen to 60s and 70s Greatest Hits. 6IX got a restricted, low power FM license for the northern suburbs (105.7MHz) a few years ago, but the transmitter is not co-sited with the TV stations, so unless you bought a separate antenna and pointed it at the 6IX transmitter, reception has not been good.

Finally, at last, 6IX is now on the digital radio band! Oh frabjous joy, I can get decent reception at last! Unfortunately the ABC isn’t there yet, but they assure us they’ll be on digital on July 1. DAB+ receivers are a little expensive at present ($195 is the cheapest) but they should come down. There’s no car radio version yet, but I live in hope.

Boring technical stuff, sorry. There’s a lot more I could write about all this, about the politics and shenanigans that have gone on, as well as the interesting techo details. If you’d like more, please leave a comment below.

Cheers, PC