Earth leakage fault?

Afternoon all.
A couple of months ago I picked up a 2013 A4 Avant B8. Quite excited with the prospect of DAB in the car Ive been pretty disappointed so far with the reception.

Anyway, after trying various things, whilst messing with the radio on the drive this evening, I noticed that the reception instantly improved when the ignition was turned off and instantly played up again when switched on.

Must admit I wasn't expecting these kind of faults from a premium brand with sonething as simple as a radio.

Could it be an earth leakage fault? Has anyone cone across a similar thing?

The in cat unit is a factory Concert.

Any help greatly received.

Cheers Jon

Ps, car still under warranty with car supermarket I got it from.

Scratch that.
Just sorted it.
It turned out to be the twin USB charger I had in the 12v Aux port under the arm rest. Once removed it's all spot on.

Live and learn.
Cheers Jon.