Buzzing sound

[Joerg Reisenweber]

Am Di  5. August 2008 schrieb Jeffrey Ratcliffe:
> 2008/8/5 Andy Green <andy at openmoko.com>:
> > Like Ole says when I started looking at it, by calling a landline in the
> > same room and listening to its receiver lying on the desk, it varied
> > tremendously and not in a repeatable way.  Eg, it appeared to vary by
> > orientation of the phone, but when I traced the path backwards, the buzz
> > did not return.
> 
> OK. Confirming this - the buzzing seems to come and go in waves of
> varying frequency. Even without touching the phone, the buzzing just
> comes and goes.

I noticed the buzz come and go in discrete steps. I guess that's basestation 
sending PCF commands to mobile, to level up/down the TX-power.
BS decides on this depending on signal-quality of MS as BS sees it.
It would be *very* helpful to confirm this, by using some RF-meter (e.g. 
microwave leakage tester?), and/or reading the battery current, while 
observing the noise come and go-

> 
> > Also, I had to keep whistling during this to provoke transmission
> > actions that seem to be the start of the issue.
> 
> You obviously need a signal generator for repeatability - unless you
> have perfect pitch...

Nah, that's just to give some data to GSM-chip it has to transmit. Otherwise 
it will enter dicontinuous transmission mode, means simply stopping to 
transmit as there's nothing but silence we had to send to the other end.
So the actual pitch is irrelevant. Any kind of noise will do, as long as it's 
loud enough.

cheers
jOERG
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