DAB radio is brilliant, BUT, it doesn't travel well. If your DAB radio is losing signal strength then it's likely the antenna amplifier is faulty. The amplifier boosts the signal strength without which it would be weak, or even non existent in many places. They're usually located directly underneath the antenna so you'll need to at least partially remove the roof lining. It may have got wet if water is getting under the antenna. The amplifier should have a 12v supply and needs a good earth connection. If you have both then the amplifier has probably failed.

Many thanks for your reply.

I was surprised to find a conventional rod aerial and not a shark on the car roof.

Ive fed some contact cleaner after removing the rod and there was some improvement but from what you say the problem is in the base and may need removing to check ?

Is it worth trying a new rod antenna ?

Yes you could. If you live in a strong DAB signal area it should work fine, but as soon as you drive through an area where the signal is weaker you'll lose it. That's why you need an amplifier.