Becker Mexico 874 radio and single CD
 

As long as I have owned my 1990 500SL, single CD's play fine, but
the radio tends to crackle as if the radio station is weak. Compared to other radios in other cars I own, even other Mercedes, radio station reception is poor in this unit.
Has this radio a reputation for poor performance, or can it
be internally tuned to optimize reception? If some tuning is
possible, can someone advise exactly how it is done?