Before that I rewired the power supply for the radio from different sources on the fusebox ( switched/unswitched). Source directly from the battery. I checked the grounds everywere. Placed different suppressors. Installed a new alternator.
All the above didn't help and the interference...
The problem is solved !!!
It's been a while since I had this "interference" problem. I left it for what it was and paid no attention to it anymore.
Untill I changed the sparkplug wires as they were on the engine for as long I own the car (17 years..)
And thát did the trick, no interference...
I ordered a set from ACC for my Newport. The Chrysler logo was allready included.
I took them to a embroidery company and they embroidered "Newport" on it.
Here a some pics: