Buzzing on GSM audio
joerg at openmoko.org
Sat Jul 26 07:24:05 CEST 2008
Am Sa 26. Juli 2008 schrieb christopher bradski:
> Just curious if there is a gsm "saw filter" somewhere in the audio path (or
> another filter by the amp)?
Not quite sure what you mean by saw-filter, but i guess the answer is "No".
> Also, I haven't popped open my freerunner yet
> but could another fix be that a small capacitor could be strategically
> placed to filter out the noise (like the sd card issue (worked in my car
That's our big hope, but so for all investigations/reworks (there were quite a
few) didn't yield the results we needed.
> Sorry for so many questions/possibilities... Is the Vcc path to
> the gsm transmitter to close to an audio path
Yes it is (near bat-con), but we seem to have made clear it's not the source
of the problem. The problem can be triggered by introducing external RF
(second cellphne e.g.), so internal VCC-issues are off he list.
> or could it just be something
> is tied down to an incorrect ground location?
> I'm sure the Openmoko team is
> already on top of this though.
Bet we are ;-)
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