Simon,
Aerials for various things can get very complex very quickly, but (being perpetually short of money, as always) once I had bought a nice second-hand DAB radio (Blaupunkt Woodstock - very highly recommended and easily available on eBay) I needed an aerial for it at short notice. I knocked up a simple dipole of the relevant length (313mm for UK DAB) and it picks up six multiplexes quite happily in and around London, dropping out only when going into long tunnels and whatnot.
I bought the right connector for the back of the radio - this varies from brand to brand, but the one for Blaupunkt kit is an SMB (female). I bought from DAB On Wheels, who were excellent - not expensive, cheap delivery and prompt service. Getting the right connector is important, and their list of connectors is here:
http://www.dabonwheels.co.uk/browse.asp
I attached a piece of TV co-ax cable to this, such that the inner part of the co-ax was connected to the inside pin of the SMB connector and the shroud to the outside of the connector, and ran this across behind the glove box to the bottom of the passenger-side A-pillar. I then ran a single 313mm length of 1amp copper cable from the inner part of the co-ax up the A-pillar, making sure that no part of the aerial connected to anything else (car bodywork/other wiring etc).
You could improve the aerial a lot if you added a second 313mm bit of wire parallel to the first one, but heading down (making a T-shape), and connected to the shroud rather than to the inside of the co-ax. You could improve this still further if you made the aerial stand vertical (the polarisation of the DAB signal is vertical, but the A-pillar isn't), but in practice this simple aerial worked much better than I expected it to, and I am very pleased with it.
I'd put some photos of it up ... but I didn't take any! However, here is a nice photo of the radio in my dashboard. I think it suits the design of the car quite well - certainly doesn't look as out of place as other radios. And it has a subdued colour scheme when illuminated, which helps a lot!
(If anyone does want photos of the aerial - and it just looks like a manky bit of wire, but there we are!) then I can dig it out and take some shots. But you will have to owe me a beer for doing so!)
Oli.
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