Radio reception weird

[Maxis]

Hello, this is my first post on this forum so please be kind..
Ive brought mysef an audi A8 d2 2002 and have some faults with it that iam tying to sort a i go along.The most annoying one is no reception on the radio, its a symphony with the front loading cd multiplay.
When the car (radio) is cold the recepton is fine but as the radio gets warm with use after about 10 mins or so the reception fades out till its gone completely.
I have checked all conections at the back of the radio and all are ok.
I have changed the diverstiy switch in the n/s c pillar with one i got from A8 parts but still no joy.
Any help would be cool? Many thanks