Point taken Erik, but in this instance, what was the purpose of the ferrite bead? Methinks it is to stop too much RF from the operation of the micro finding it's way into the VCC track and being radiated. In terms of susceptability, I think putting a ferrite bead near the micro is probably the wrong position - I would hope that we'd taken care of that further upstream!
I try to keep my comments brief, although this may entail cutting short the 'full story'. Put it this way, would you put a ferrite bead on a micro running at 4MHz? As yet, I haven't found it necessary - time may prove me wrong. At 20Mhz it would bear consideration. Putting a ferrite bead on incoming power? Along with some protection and filtering, yes!


I made a few other points for discussion, but as yet, no response.