GSM-noise "buzz" issue

Joerg Reisenweber joerg at
Mon Aug 11 14:06:55 CEST 2008

To keep updated all those who are interested in details:
Seems we finally found enough of the working mechanism of GSM-interference, to 
promise we will be able to stop it.
More details: JK4401 hs-receptacle isn't shielded and obviously the contact 
springs catch RF and feed it to the audio-path. Pin4 (MIC) is our suspect #1 
so far. We are about to test different reworks to fix the issue for the 
different classes of devices (like: sold A5, already produced A6, still to 
SMT A6, A7 prototypes). 
So far our results on tests (only tests with positive results mentioned ;) 
removing JK4401 seems to stop noise completely (obviously no option for a 
fix ;-).
Shielding JK4401 with copperfoil-sticky, which is connected to GND by 
soldering it to nearby can, yields some reduction of noise, but isn't 
sufficient to ultimately fix the issue. Also won't help on noise via 
connected headset.

I will keep you updated.
Please note all this IS NO RECOMMENDATION FOR A REWORK, and we can't answer 
any questions yet beyond what I've reported above.

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