GSM-noise "buzz" issue / GPS coupling
joerg at openmoko.org
Fri Sep 19 19:14:30 CEST 2008
Am Do 18. September 2008 schrieb Andy Green:
> There is definitely a story waiting to be uncovered here. On my GTA02
> A5 "skelephone" that is just a PCB, I replaced plastic GSM antenna with
> "random piece of wire". The buzz comes fine. "Over the air"
> contamination does not involve antenna radiation pattern then, it is
> suspicious. It means PCB inherently couples "something" "somewhere"
> before antenna. I keep going back to power rail-borne contamination but
> it doesn't fit with beads doing something on headset nets.
Not "doing something" but actually stopping noise completely, according to Len
We also heard noise is stopped by connecting external GSM-antenna, as well as
by removing JK4401, and I managed to induce noise by "alien" RF fed to the
phone (actually near hs-jack JK4401) by using some test-phone placed near to
Power-rail has been examined by me for a whole day more than 2 months ago:
So I don't exactly get it what's your conclusion from replacing
plastic-GSM-ant by a "random piece of wire". Especially I don't know
about "antenna radiation pattern" of this wire and how it should differ from
the one of plastic-antenna. Actually probably nobody can tell exactly about
the particular characteristics incl radiation pattern of any antenna setup,
until you actually did decent research on a prototype. That's the main
culprit for RF-design resembling black magic rather than logic-based EE.
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