You can try this below and see if the reception is improved.
This is from the Tech Service Info.
Poor reception with radio BMW Business CD RDS (world device CD 43)
Cause: Incorrect reception area set.
Radios concerned: Business CD RDS (world set CD 43)
Situation: The Business radio CD RDS (world device CD43) is designed for all reception areas in the world. If the right reception area is not set in the radio menu ”AREA”, the result can be poor reception.
Action: Setting the reception area
Procedure: Initial commissioning of the radio (replacement device, new device)
Fit replacement radio in vehicle and switch on radio.
The message ”NO AREA” appears in the radio display (only during initial operation of the radio)
Now switch to the required region (”Europe”, ”USA”, ”Canada”, ”OC+RDS”, ”Japan”).
a) On E46 radio and DIN unit with ”Station button 1”.
b) On E39 radio with first softkey (Station button 1).
Now switch off radio (AREA is saved).
Procedure: Changing a reception area that has already been set
a) On E46 and E39 radios
Switch on service mode (switch on radio and press ”m” button within 8 seconds)
Now press the ”+ button” as many times as required until ”AREA” is displayed in the radio display.
Use ”Station button 1” now to select the suitable AREA in the menu and switch off the radio (AREA is stored).
b) On DIN radio
Same procedure as for E46, E39 radio
On the DIN radio, depending on the set reception area, a CODE input might be necessary after the changeover.
cheers and let us know if it works.