GSM-noise "buzz" issue FIXED, but not in MP?

Joerg Reisenweber joerg at
Mon Sep 22 00:55:25 CEST 2008

Am So  21. September 2008 schrieb Werner Almesberger:
> Uwe Klein wrote:
> > I had thought about using the FR as an energy sink.
> > Using a 4pole networkanalyzer and a pair of antenna
> > in a grid dip meter style arrangement.
> > This should indicate all absorbtive elements.
> My heart filled with joy upon reading this. You didn't exaggerate
> about your lab being very well equipped :-)
> Let's hope Andy or Joerg can find something.
> Thanks,
> - Werner

I've never seen us investigating thus deeply and time-consuming on a 
certified-to-work fix anytime before, just to study *why* it's working.
Probably that's what Graeme called "be happy with just doing tests".
Alas I don't have any spare time for this kinda joy. I like to sell a 
high-quality (=bug-fixed) product *now*.
Only answer I'm interested in is: why don't we already have those 
beads/EMI-filters in GTA02A7, though it's been validated to fix buzz since 
more than a month now, and we seemingly all accepted it's a viable fix for 
GSM-buzz (or at least we agree it's safe to have those beads even for GTA03: 
U4906, U4907!)? When are we going to give them a try on GTA02? Is anybody 
assuming we could spoil GTA02 design to a point where even replacing those 
EMI-filters by 0R would break the device?

I urgently recommend to start to do a PCB with pads for EMI-filters *now*.
I absolutely veto on producing GTA02 with a 100uF on C4306.
@Sean: you asked me to solve this issue. That's my result for now.

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