I suspect your lack of antenna extension is causing the radio static.

On the back of the radio (I assume you have a Becker 780) there is a single blue wire with a quick connect. It has a black sheath on it so you may mistake it for a black wire.

Make sure that is plugged into the radio. It goes next to the power connector.

In the trunk make sure the connector is plugged into the antenna.

Antenna is fed from fuse C but if your dome lights and door locks work that isn't your problem.

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech