Subject: (Philip) (Curry)Modulated signals (or pulsed???) (fwd)
Date: Mon, 18 Jan 1999 133627 -0600 (CST)
From: "Roy L. Beavers" <rbeavers@llion.org>
To: emfguru <rbeavers@llion.org>
--------------------------------------------------
Hi everybody:
This is a terribly important message in my opinion!!!
In his message below, Alasdair is commenting on the "modulated vs pulsed"
issue which Dr. Curry raised earlier....
I have marked one of Alasdair's statements below, thus: ***
The importance of the statement I have highlighted (below) needs to be
applied _across the entire spectrum and range of EMF exposure_!!! We are
receiving so many different exposures, often simultaneously (and perhaps
with chemical exposures), that the differentiations (in
exposure/effect) which "science" has tried to distinguish, so far,
could be almost entirely irrelevant!!! To the present, the "science"
efforts have been very primitive and on a one-to-one basis....
It is as important to understand this aspect as it is (may I remind you
again) to understand the "myth" of low risk factors which results from the
ubiquitous presence of EMF throughout the environment of industrialized
societies ... even (to some extent) the less industrialized societies....
NIEHS and others who are responsible for future research (if there be any)
need to think about this!!! I would like to hear from some of our EMF-L
scientists as well on this!!! When you read Alasdair's paragraph below,
I believe what I am saying here will make more sense....
We need to acknowledge that man's exposure to EMF is rarely on a
one-to-one basis. Normally man is 'swimming' in a milieu of different
EMF exposures..... Different frequencies. Different signal "shapes."
Different energy levels. Different pulses or modulations, etc.....
Cheerio.....(Many thanks for this, Alasdair! When I get something like
this -- it really encourages me to keep this list going!!!)
Roy Beavers (EMFguru)
rbeavers@llion.org................
...It is better to light a single candle than to curse the darkness...
.................PEOPLE ARE MORE IMPORTANT THAN PROFITS...............
---------- Forwarded message ----------
Date: Mon, 18 Jan 1999 18:40:06
From: Alasdair Philips
To: "Roy L. Beavers"
Cc: "Bill P. Curry"
Subject: Re: (Curry)Modulated signals (or pulsed???) (fwd)
Bill & Roy & everyone:
I think you can describe this as a "techno-rant"...........
All the main analogue systems (NMT, JTACS, AMPS, ETACS, etc) were FM.
No reports of mental problems with these (eg memory, concentration, etc)
though some suspicion of brain tumour promotion or even cause.
The digital systems are very complicated. As you state GSM (& DCS) gives
off primarily 217 Hz (+ LOTS of harmonics) and has GMSK (Gaussian Minimum
Shift Keying) modulation which actually is a sort of FM put out in
time domain bursts every 4.6ms. Because the transmitters keeps
powering off & off you also get real ELF magnetic field pulses of
up to 6 microtesla (60mG) into the side of the user's head!!
(again, 217 Hz + high harmonic content)
US Digital Cellular (IS-54) is again TDMA this time using
quadrature phase modulation(QPSK). The pulses have a square-root
raised cosine spectrum with 35% excess bandwidth.
NADC and PDC use pi/4 QPSK modulation with pulses at 50Hz repetition rate.
ESMR uses 16-QAM modulation. This is a 16 point Quadrature Amplitude
Modulation obtained by separately modulating the amplitude of components
of a sinusoidal carrier differing in phase.
CDMA again uses QPSK but encodes the speech as QCELP resulting in a spread
spectrum signal very similar to an noisy analogue AM signal. This broadcasts
all the time and doesn't have a local ELF pulsing nature.
Iridium uses DEQPSK modulation with time domain pulses every 90 ms!!
(11.1 Hz !!! ugh!!!! brainwave region)
Do you get the feeling, like I do, that I am getting to be "an old
fogey", left behind on the sands of time. Trying to understand what
all these different systems do really makes my brain hurt.
[.....Here it is.... guru....]
****And, of course, they are all likely to have DIFFERENT bio-effects!!
Great for confusing the epidemiology so that "no clear pattern" of
health problems emerges!! Hence no "official" and "clear" problem.****
So my advice always is avoid them all!
[....."Avoidance" again.....guru.....]
Alasdair
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alasdair Philips (aphilips@gn.apc.org)
Director, UK Powerwatch,
EMC Engineer and EMF-bioeffects researcher
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
At 13:17 13/01/99 -0600, you wrote:
>
>---------- Forwarded message ----------
>Date: Wed, 13 Jan 1999 12:40:35 -0700
>From: "Bill P. Curry"
>To: "Roy L. Beavers"
>Subject: Re: Modulated signals (or pulsed???)
>
>Roy,
> I would like to inquire of your readers whether anyone knows whether the
>fodulation technique for cell phones is amplitude modulation or frequency
>modulation. I am ignorant on this score. If the carrier wave is amplitude
>modulated at audio frequencies, then I think the situation resembles the case
>of the digital PCS phones, which employ pulses at a pulse repitition
>frequency near 200 Hz.
> I think the significance of this is the following: 1) Experiments
>carried out (I think) at Columbia University have investigated a range of
>frequencies to determine sensitivity of bioeffects caused by sinusoidal
>EMR to frequency.
>
>As I recall, the range investigated was from 0 to several thousand Hz, but
the
>range of greatest sensitivity was from 0 - 500 Hz. Note that the pulsing
rate
>of digital PCS phones is around 200 Hz and well within the frequency range of
>greatest sensitivity. 2) Since cell phones are not high fidelity audio
>devices, the range of audio modulation frequencies i n cell phone
>transmissions is probably about 40 Hz to 8,000 Hz. (A high fidelity audio
>system would be about 20 Hz to 20,000 Hz - slightly beyond the range of human
>hearing.) Thus, amplitude modulation at the audio frequencies also covers
the
>range at which there is sensitivity of bioeffects to EMR. 3) By Fourier's
>theorem, any complex wave form - whether it be a rectangular pulse or an
audio
>modulated signal - can be decomposed into an infinite number of sine waves,
>each of which has a particular frequency and a particular amplitude. Because
>the majority of information in this expansion is carried by relatively few
>terms in the Fourier series, the infinite series effectively becomes a finite
>series - one with relatively few sinusoidal terms (This is the principle on
>which the Fast Fourier Transform method of analyzing dynamical response fo a
>system is based.) Thus, either a series of pulses or an audio modulated
>carrier wave will be equivalent to a number of sine waves (of different
>amplitudes) whose frequencies cover the range in which bioeffects have been
>found to be most likely.
> If, on the other hand, cell phones use frequncy modulation, instead of
>amplitude modulation, then I don't know how to analyze the situation, but I
>speculate that bioeffects would be less likely than with amplitude modulation
>(assuming there is also no pulsing). I would like to see yours and your
>readers' comments on this.
>----
>Bill P. Curry, Ph.D. |Physics is fun.
>EMSciTek Consulting Co. |Trying to make a living!
>22W101 McCarron Road, |Phone: (630) 858-9377
>Glen Ellyn, IL 60137 |Fax: same, but require prior notice
>
> Home page: http://www.EMSciTek.com
> ____________________________________________________
> | Analysis, experiment design & software development |
> | for engineering and the physical sciences |
> ----------------------------------------------------
>
>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alasdair Philips (aphilips@gn.apc.org)
Director, UK Powerwatch,
EMC Engineer and EMF-bioeffects researcher
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Archive provided courtesy of WaveGuide, http://www.wave-guide.org
Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html