Joseph wrote:
> On Thu, 03 Mar 2005 15:59:30 -0500, Ted Koppel <tkoppel@adelphia.net>
> wrote:
>> My new Nokia 6010 has an interesting and somewhat annoying habit. If
>> it's anywhere within a 5 foot radius of my PC speakers, I can hear it
>> periodically transmitting something (sort of a rhythmic
>> dum-diddy-dum-diddy-dum-dum-dum). Sounds like static, but definitely
>> with a paced rhythm. I haven't timed the intervals exactly, but it
>> seems to take place every 17-20 minutes. In a related activity, I
>> hear a big burst of static on my PC speakers, and then some rhythmic
>> noise, about 5-7 seconds before the cell phone begins to ring.
>> This is the first cell phone I've had that caused these noises. Do I
>> have a mutant phone? Is this anything to be concerned about?
> It's not just the Nokia 6010. *Any* GSM will exhibit the
> characteristics you refer to. It's the phone communicating with the
> system periodically. You'll hear the buzz-buzz even more when the
> 6010 is ringing. You'll hear a different type of interference when a
> TDMA phone rings (more like a low hum.) It's normal and your phone is
> not defective.
> [TELECOM Digest Editor's Note: The first time this happened to me, I
> was walking around downtown. My cellular phone (and its holder) were
> clipped on my belt. Right next to that was my Walkman FM radio which
> was also clipped on my belt, and I was listening to it through my
> headphones. Suddenly the radio started humming and buzzing, as though
> there was some interference nearby. I wondered to myself, what is
> going on there in Potts (I was walking right past the Potts Funeral
> Home when it started). I got a few steps beyong Potts and the inter-
> ference stopped. I found out later it was a call coming in on the
> cell phone; apparently the cell tower had been trying to locate me for
> the call. I did not realize it at the moment, and just thought it was
> some kind of spurious interference noise. But later at home, I sat the
> cellular phone on a table next to my Bose radio, and I was not wearing
> my headphones (so I could hear the phone 'ringing' [or actually
> giving its electronic chirp of a call coming in]) and the Bose radio
> did the same thing: played a spurt of interference noise when it was
> happening. I just assumed either the cell phone or the Bose radio was
> faulty. Your explanation helped explain it. PAT]
This kind of interference is specific to phones which use a TDMA (Time
Division Multiple Access) protocol (such as GSM), where the phone
transmits only during its time slice several hundred times per second,
resulting in a pulsing which causes the observed interference. CDMA
(Code Division Multiple Access) phones, when they are in a call or
doing occasional bookkeeping with cellular system, transmit
continuously over a wide frequency range (1.25MHz, for example), and
do not cause interference like this. In fact, without knowing the
specific pattern being used by the phone, it is practically impossible
to distinguish its signal from background noise. Which is one reason
(along with the difficulty of jamming it), that the military was
interested in CDMA long before there were cellular phones.
CharlesH (hoch@exemplary.invalid)