Noise on AM/FM radio - source?

[SuperMono]

Before I go randomly looking for loose wires and corroded grounding points has anyone had a Freebie radio go feral with substansial engine speed noise on AM in particular but also noticable on FM and faintly on CD?

If so give me some pointers before I break something difficult to put back together :)

[Blknight.aus]

my moneys on a diode in the rectifier bridge in the alternator letting go.

[pk.hoarder]

If the diode/alternator angle doesn't work, check for loose components near the alternator or ignition system - maybe a suppressor or filter has lost its earth connection. Don't know Freebies very well - do they have an electric fuel pump? If they do, check for bad earth or loose components near there too.

If you don't see anything there, it may be that a filter has lost its earth near the radio itself.

A handheld AM radio might help you locate the source (or it might just confuse things since sometimes the noise seems to come from everywhere - once it is on the power wiring it probably couples through the whole car).

Good luck with it - I will be offline for a week or so, I'll read all about your triumphant success later...

Cheers

Paul.