GSM-noise "buzz" issue

Andy Green andy at openmoko.com
Mon Sep 29 18:52:00 CEST 2008


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Somebody in the thread at some point said:

| 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 :(.

I know what you mean about it coming and going, seemingly disconnected
from what you are doing to the phone.

I was looking at the VB_SYS rail during the buzz time a couple of months
ago, it seemed to me the buzz came and went according to what I saw on
VB_SYS.  But this was an A5 revision.

| 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.

At high frequencies "shorts" with some loop area don't necessarily have
that low an impedence.

What did you actually short to what, everything to the 0V pin really?

- -Andy
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