Thanks. Mine is a convertible (should have put that in the heading sorry) - does any of your advice change in that case? It has the antenna on the nsr wing.Two common failure points in the E46 :
- The diversity amp in the rear C pillar. http://www.realoem.com/bmw/showparts.do?model=AV52&mospid=47644&btnr=65_0480&hg=65&fg=30 Item 2.
- The element itself - requires a new rear window.
Does the reception change when the rear window demister is on? If so then it's more likley the later.