GSM-noise "buzz" issue

Florian Zeitz florian.zeitz at
Mon Sep 29 18:21:11 CEST 2008

Hash: SHA1

Werner Almesberger schrieb:
> I wrote:
>> Florian Zeitz wrote:
>>> FWIW I have tried something similar. I put a small (100 Ohm IIRC)
>>> resistor between MIC and GND, that doesn't help at all though. It just
>>> makes things worth.
>> :-(
>>> If you think it's more likely to work I can try a
>>> short everything or a completely different approach (still have two
>>> 2.5mm jacks lying around) if you want.
>> I guess it can't hurt to try our luck, even though it seems unlikely
>> this will help. I'd go for the "short everything" variant. The
>> amplifier is protected by 33 Ohm resistors R4405 and R4407, so this
>> should be safe.
> Did you try it ? Joerg has suggested that this experiment may actually
> be quite promising. So what's a wasted EUR 1 component compared to the
> possibility of eternal fame ? ;-)
Got around to try it just today.
The problem for me with testing is that I (too) have a pretty good
signal where I life (Actually orignating about 300m away ;) ), so that
if there is buzz it is relatively silent.
To reproduce it reliably I just went into the cellar and did a longer
test call. Interestingly the buzz was sometimes pretty loud and
sometimes hardly present which did not seem to coincide with the signal
strength. Actually once I noticed the buzz getting louder when the
signal got stronger oO. What I annoyingly had all the time was a pretty
loud echo though :(.

As for the shorted plug: If there is buzz it amplifies it a tiny bit, if
there is no buzz it doesn't seem to induce buzz, but it definitely does
not seem to make things better.

> Oh ... Andy, did you try a shorted headset plug ? Given that you're
> one of the lucky few in Openmoko who can actually reproduce the
> buzz ...
> - Werner

Version: GnuPG v1.4.6 (GNU/Linux)


More information about the hardware mailing list