Subject: Re GSM phone (fwd)
Date: Thu, 19 Mar 1998 101837 -0600 (CST)
From: "Roy L. Beavers" <rbeavers@llion.org>
To: emfguru@hotmail.com
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---------- Forwarded message ----------
Date: Thu, 19 Mar 1998 16:34:49 +0100
From: Clas Tegenfeldt
To: "Roy L. Beavers"
Subject: Re: GSM phone (fwd)
At 13:50 1998-03-18 -0600, you wrote:
>Date: Wed, 18 Mar 1998 17:55:29 GMT
>From: Alasdair Philips
...
>The GSM phones were working at full power during the tests. This is 2 watt
>pulse power with an 8:1 duty cycle at 217 Hz. Hence the "average" power is
>only 0.25 watt. An analogue phone (ETACS, etc) at full power output 0.6 W.
>Many of us think it is the pulsing rather than the actual rms power that is
>the problem with GSM phones.
>
>For completeness, GSM and PCN digital base-stations do NOT pulse - they fill
>all used time-slots with dummy data. This was to minimise EMC and RF
If you listen to a the demodulated signal from a base station you definitely
hear a pulsed characteristic signal! You can easily recognize this signal
even in presence of all other radio signals usually to be found. So, even
if the base station fills out the slots with dummy data, the broadband signal
still has a low frequency amplitude modulation... Anyone with a spectrum
analyzer
with builtin AM detector (and broad filters, preferably >1MHz) can verify
this, or just use active antennas and a suitable broadband diode detector and
amplifiers (which is what I mostly use).
So, GSM uses a complex modulation with a complex set of data transmitted, it
is a lot going on. In the end we have a signal at around 900 MHz which has
various low frequency components, you can easily hear components in the
kilohertz area which are coming like bursts. The easiest way to descibe
the GSM signal is to say it is GSM...
Clas Tegenfeldt ,,,
(o o)
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Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html