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PURE Digital's Highway takes the digital out of digital radio... or does it?

by Steve Kerrison on 17 December 2007, 13:56

Tags: Highway, PUREDigital

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Here I am, sat writing code, because the boss says if I don't then all I'll get is a lump of coal for Christmas. To stop me from tearing out my RAID array and smashing it to pieces because I keep accidentally running SQL queries that return millions of rows, I'm listening to theJazz on DAB digital radio.

In the ad breaks, PURE Digital's running ads about its amazing new digital radio for the car. But it's not really digital. Well, it is, and it isn't...

The Highway is a DAB radio for vehicles. Portable and digital... sounds awesome! But replacing the old stereo will be a right pain in the arse, right? When the advert first hit my ears, I was somewhat intrigued by the line that goes something like: "You don't have to touch your existing car radio" - it works with it.

Instantly, I smelled a rat. If the Highway uses the existing sound system and head unit, then it must do one of two things. The first is connect up via a cable, like an MP3 player might - something not all car stereos have. The second is to use the same method as iPod transmitters, and that's to use low-power FM radio.

Sure enough, the Highway's web-page reveals that it uses FM to deliver DAB digital radio over the hop between itself and the car stereo. It's even got an audio input so you can use it with your iPod.

But the problem, of course, is that FM ain't digital. So what is PURE thinking?

Well, believe it or not, I'm not here to shun PURE. To understand why, you need to know a few facts about DAB.

PURE Digital Highway

The Highway - It doesn't matter if it's not digital all the way... DAB's worse than FM anyway.

DAB, as a digital transmission system, is more efficient than the analogue FM scheme. You can send more data in a smaller space of spectrum. That's a great thing to be able to do. It means you can broadcast more channels and do so at a higher fidelity... if you get the balance right.

But that's not what is done. DAB channels are, generally, highly compressed MP2 channels. We're talking 128kbps-160kbps generally, with a few exceptions. It means broadcasters can fit a lot more stations into their allocated spectrum, but the quality is actually worse than FM.

That's right, if you have two strong signals, one DAB, one FM, the FM one will sound better.

So, the fact that PURE has used FM for the last hop of its Highway product doesn't really matter, assuming there's some free spectrum somewhere for the FM transmitter to work on without interference.

DVB-T television is the same - highly compressed streams so they can fit in tat like shopping channels and videos of ladies frolicking. It looks likely (in the opinion of some, at least) that the extra spectrum freed up by the analogue TV switch-off will be used to broadcast more compression-artefact-riddled crap, rather than some high quality HD channels.

So my complaint here isn't with PURE's Highway, which likely won't impede the quality of the DAB radio stations it receives. It's the broadcasters, beaming it out in such a poor condition that it really won't matter what you do with the audio for the last metre or so.

But what can we do about it? I'm lost for ideas, so do please let me know what you think!

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As an aside, I'm listening to theJazz over the Internet, which uses WMA9.1 at 128kbps. Not sure if that's better/worse/the same as 128kbps MP2, I'd wager slightly better, so let's hope it's not transcoded from the MP2 stream.
Someone has to ask…

By MP2, do you mean Mpeg-2 (but not audio layer 3?), or Mpeg 1 audio layer 2?

Or even possibly Mpeg 2 AL2?

Not being a pedant, just wondering :rolleyes:
I mean MPEG-1, layer 2.
I think this is a good thing.

DAB in the car is very limited and usually expensive. Most car audio manufacturers have a DAB addon for their head units, adding at least £100 to the cost of upgrading your head unit. And with the number of car manufacturers building the stereo completely into the center console, replacing it is becoming a lot harder.

If this makes it easier to have DAB in the car, and more people become acustomed to having DAB in the car, then car manufacturers will be forced to at least have dab as an option, precious few do at the moment, and often only on the higher end o the range.
DAB radio is low quality, everyone knows an for some strange reason, accepts this. The quality of radio3/classic is frankly awful. But in a car who gives a **** you're not going to be able to truely apprechate that motzart because a hammer drill digging up victorian water mains beats flute. And sure as rock beats scsissors the sound of your cars engine, the fact that your moving at, obviously no more than the speed limit, will also help ensure everything sounds crap.

Audio in cars is always awful, enless you've got a roller, in which case the damn clock is making too much sound :P