GSM-noise "buzz" issue
steve at openmoko.com
Tue Aug 12 18:27:23 CEST 2008
From: Joerg Reisenweber [mailto:joerg at openmoko.org]
Sent: Monday, August 11, 2008 5:07 AM
To: hardware at lists.openmoko.org; steve; sean at openmoko.com
Subject: Re: GSM-noise "buzz" issue
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
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
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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