SLK 280(R171)

[PC7]

I cannot get any decent radio reception at all even when in a strong signal area.
The car has the command sat nav (in case that makes a difference) but despite reading the manual I cannot get anything beyond a load of fuzz.
The ariel is connected to the base (can't comment on behind the panel on the wing or rear of command unit).
Help pls - I must be missing something really obvious

[Dog Star]

I believe there's an amp for the antenna somewhere - is there a fuse designated for it.
Otherwise I really would suggest looking behind the unit and the panel.