The third-generation Nissan X-Trail is arriving in Australian showrooms now, and along with its less utilitarian styling, the new mid-sized family SUV features digital radio in its mid-level ST-L and top-spec Ti models.

Lexus digital radio screen

So, now is as good a time to answer the questions: What is digital radio? Is it any good? And which cars have it?

Background

As the name implies, digital radio is traditional analogue radio with a twist. In analogue radio, a sound wave is transformed by either amplitude modulation (AM) or frequency modulation (FM) into a signal that can be blasted out from a transmission tower. All a radio has to do is reverse the transformation and — voila! — you have something very nearly like the original sound wave.

For digital radio, the original sound wave has to be converted into digital form and compressed before it's sent out over the airwaves. The required compression is part of the reason why digital radio (and television too, when it existed) is always a few seconds behind its analogue counterpart.

As with television, Australia was a bit slow on the uptake. Digital radio was introduced into Australia in 2009, years behind many countries in Europe. As a consequence we’ve adopted the DAB+ standard, whereas European countries use the earlier DAB (digital audio broadcasting) protocol instead. DAB+ uses a newer form of audio encoding that can cram more sound into less space and it also handles interference better.

A consequence of this is that many car makers had to wait for DAB+ capable head units to come down the corporate R&D stream. This meant until 2011 no cars were offered for sale in Australia with working digital radios. In fact a number of European marques have sold cars in Australia with the words "digital radio" emblazoned on the head unit, but which were incompatible with the DAB+ standard.

When is analogue radio getting phased out?

There’s no need to panic, there are currently no plans to switch off analogue radio transmission in Australia, meaning that current car radios will keep working for a long while yet.

This situation contrasts quite markedly from what happened with television. Australia finally shut down the last of its analogue TV transmissions at the end of 2013. The federal government is currently in the process of selling off the airwaves slices which the TV networks used to occupy to telecommunications companies for future mobile services.

Goodbye static

The biggest improvement over analogue is digital radio’s clear, crisp sound.

A lot of things impede or bounce radio waves around as they make their way out from a transmission tower to your car: Tall buildings, hills, mountains, other transmitters, generators, electronic devices, and a very small fraction of the noise created by the Big Bang. All of this noise and delay is picked up by an analogue radio receiver.

With the laws of physics being what they are, these same issues affect digital radio signals. Thanks to the error correction code that's built into the DAB+ specifications, however, digital radio is free from the static and crossed signals of its analogue counterpart.

Reception is all or nothing

Like digital television, digital radio is an all or nothing proposition. If the signal quality drops below a critical level, reception drops out completely.

In town this typically happens when you drive into an undercover car park or through a tunnel. In the suburbs on the fringe of the reception area there will be frequent and annoying drop outs.

By comparison analogue radio will slowly degrade to background static as you drive out of town. While in a car park you may still be able to discern key items in a news bulletin, the announcer’s call of “it’s a goal!” or the rhythm of a tune over the crackle of static and interference.

Improved sound quality … for some stations

If your radio diet consists mainly of AM stations, you’ll notice a massive increase in audio quality with digital radio. Presenters and guests sound refreshingly human, while music doesn’t feel like it’s being played through a tin can and down a piece of string.

Move over from FM to digital radio and the difference isn't quite as marked. The lack of hiss and static is immediately apparent, but some stations may actually exhibit poorer sound quality than an analogue equivalent. That’s because some stations are transmitted at higher compression levels to minimise the amount of broadcasting spectrum they use. In general most networks only apply aggressive compression to digital only stations.

As a bonus, digital radios usually display the current show's name, track title and possibly album art, in addition to the station ID. Some entertainment systems go a step further, allowing users to pause and rewind live radio.

Big cities only

For those living outside a mainland capital city, the lack of digital radio broadcasts is another item to add to one's long laundry list of grumbles.

Currently only Sydney, Melbourne, Brisbane, Adelaide and Perth have the full complement of government and commercial digital radio stations. In these cities a handful of community-run channels are also simulcast in digital.

Darwin and Canberra are currently in testing phases with low-power transmitters, so reception range is limited and the signal may be patchy downtown. Only commercial stations are available in Darwin, while in Canberra commercial networks, and a limited number of ABC and SBS stations are available.

More stations

As with television, digital radio encoding is more efficient at transmitting information in the same amount of spectrum. This allows each radio station owner to operate extra digital channels.

In Sydney, the ABC simulcasts 702 ABC Sydney, Classic FM, NewsRadio and Radio National on digital radio, while also broadcasting Country, Dig, Extra, Jazz and Grandstand stations exclusively on digital. Similarly, commercial operator Southern Cross Austereo simulcasts 2Day FM and Triple M, while also offering Triple M Classic Rock, Buddha, Stardust and Loveland as digital-only stations.

The official Digital Radio Plus website has a full list of stations available in every city, as well as coverage maps and updates about transmission availability.

If you’re hooked on a digital station and are venturing out of town, most, if not all, digital stations are streamed on the internet. So, all you need to do is download TuneIn Radio to your smartphone and listen in.

Which cars have it?

You don’t have to be a moneybags to purchase a car with digital radio as standard, but you're far more likely to find digital radio offered as standard or an option in a luxury brand. In fact it was Toyota, not usually a marque associated with high-tech gadgets, that was an early adopter and keen proponent of automotive digital radio in Australia.

Models currently offering digital radio include:

Pure Highway 300Di

Can I install digital radio in my current car?

If you’re not planning on purchasing one of the above cars and are dead keen on digital radio, there are a few options.

The easiest is to purchase a portable digital radio receiver and plug it into your car’s 3.5mm auxiliary jack. Pure and Sangean sell a number of portable digital radios from around the $80 mark, although external battery packs add a bit to that price.

A more elegant solution is to go for the $299 Pure Highway 300Di (pictured above) add on. The Highway features an external antenna for better reception, a dash mounting kit, dot matrix display and large buttons fit for use in a car. Output is via either an auxiliary cable or a built-in FM transmitter, although we can’t recommend the latter as it completely negates the audio advantage that digital radio brings to the table.

The final option is to replace your current car's stereo unit with a DAB+ compatible one. Yes, it's invasive, but it's what we'd recommend for cars without an auxiliary jack. There isn't a huge selection of digital radio head units available. Currently only Kenwood and Pioneer play in this space and prices go from around $250 up to $1600. Sony and Alpine used to retail DAB+ car stereos, and some may still be available in stores or on eBay.