Subject: (Curry) Some more "blue world" cell-phone measurements.....
Date: Sun, 28 Mar 1999 140241 -0600 (CST)
From: "Roy L. Beavers" <rbeavers@llion.org>
To: emfguru <rbeavers@llion.org>
--------------------------------------------------
.......3000 microwatts per square centimeter out the earpiece!!!!.......
---------- Forwarded message ----------
Date: Sat, 27 Mar 1999 12:36:58 -0700
From: "Bill P. Curry"
To: "Roy L. Beavers"
Roy,
I have some information that may bear on the question of why there
have been face and ear-related problems in some people exposed to RF - at
least for the case of cell phones.
My wife and I took our old Motorolla Micro TAC (a Flip Phone, which I
gave her before I knew anything about radiation hazards of cell phones)
and we made several fairly precise measurements of radiation power
level that may be of interest. First, note that the manufacturer states
that the phone uses frequency modulation and its signal occupies the
frequency range 824 MHz to 894 MHz. Second, note that Motorolla says the
power level varies from 0.006 watt to 0.6 watt, depending on the
conditions of service determined by the cellular phone system itself.
This disagrees slightly with some of my measurements - but that is less
important than my other conclusions.
We first measured the frequency, by dialing our regular phone
from the cell phone. The radiation probe was 3.5 inches away from the
cell phone (which was held by a C-clamp in a firm vertical position).
Because there was no audio input to cause frequency modulation (which I
have observed at other times when the phone was being used nmormally), the
phone emitted a rock steady carrier wave frequency of 830 MHz. I moved
the radiation monitoring probe vertically to sample several interesting
emission regions. First, looking only at the antenna region with the
probe 4.5 inches away (horizontally) from the phone and situated
perpendicular to the antenna axis, I found that the radiation density was
570 microwatts per square centimeter.
[Note that while this was the standard FCC limit above which phones are
not supposed to emit, that standard is enforced only in the far-field and
all my measurements were made in the near-field (since the wavelength at
the phone frequency is 36.1 centimeters = 14.2 inches, and all the
measurements were made at distances considerably shorter than this
value).]
The FCC requires the manufacturers to test in the far-field only,
because they are concerned only with interference with other electronic
devices - not with health effects, and the manufacturers must use a
standard mask that assures that their measurements will be made
only in the far-field. If we assume that the radiation density falls off
as the inverse square of the distance from the radiating element to the
measuring probe, we can invert the radiation density equation and
determine the radiated power at the source.
Doing so gives 0.835 watt radiated by the antenna, which
is slightly higher than Motorolla's stated maximum value. The absolute
number is not as important here as the relative comparison with radiation
by other parts of the phone - which I will discuss shortly. Before doing
so, however, I want to point out that some frequency components of
near-field radiation fall off with distance faster than the inverse square
law, even though the component corresponding to the primary frequency -
the carrier wave - will obey the inverse square law. My instrument is not
a complete spectrum analyzer. The instrument has a flat frequency
response between 2 MHz and 2 GHz, so all components included in that range
(and some signals outside that range as well) are included in the overall
radiation measurements, but are not identified by frequency.
The frequency counter on my instrument registers a signal that is 20
decibels stronger than any other signal, so it would probably miss
harmonics and subharmonics of the carrier frequency, though these other
frequency components (which have different inverse power fall-off
with distance) would be included in the instrument's overall field
strength and power density measurements.
Thus, I will repeat this experiment later and take measurements at several
distances, in order to determine the precise inverse power law that
applies to the whole-spectrum radiation density's dependence on distance
in the near field. Using this, I should get a more accurate power
emission value, and that may well be more in agreement with the
manufacturer's stated value of maximum power level.
The main point I want to make here is the observation that the
radiation out the earpiece and the keyboard of the phone both exceed the
radiation emitted by the antenna. [!!!! guru]
At 3.5 inches away from the earpiece,
the probe measured 3,000 microwatts per square centimeter out the ear
piece without any shielding material over the earpiece. Recall that this
value does not violate FCC guidelines, because it is measured in the
near-field, instead of the far-field of the phone. Inverting the
radiation density equation gives 2.98 watts power leaking out the ear
piece - probably because the connections of the transmitter/receiver to
the antenna are in this region and the RF field strengh is accordingly
high, unless an attempt is made to better match the impedance of the
transmitter circuits to the antenna impedance. (This is one thing the
manufacturers can do to reduce the emissions from regions other than
the antenna. When there is an impedance mismatch, signals sent out along a
transmission line to an antenna reflect back along the transmission line.
Apparently costs and, perhaps manufacturing difficulties, have kept the
manufacturers from using matched transmission lines and antennas.)
I had previously found that we got a large signl out the region of
the phone near the mouthpiece, and repeated those measurements more
carefully. This time, I centered the probe on the center of the keyboard
region of the phone, on the expectation that the cutouts around the phone
keys leak radiation. The results were surprising, to say the least. With
the probe located 4.25 inces away from the phone, the radiation density
was 240 microwatts per square centimeter. Again inverting the radiation
density equation gave an emitted power level of 0.351 watts at the
keyboard. Thus, almost half as much power as is radiated by the antenna
comes through the keyboard. Similar measurements made near the bottom of
the keyboard region - thus close to the mouthpiece - gave almost 0.8 watt,
whic is almost as much as the radiation emitted by the antenna. Further,
the radiation power emitted through the bare ear-piece is 3.6 times the
power emitted by the antenna! [!!!!!!! guru]
Some time ago, I bought a shield for the ear-piece because of my
having read on the internet that more radiation leaked through the
earpiece than was emitted by the antenna of most - if not all - cell
phones. I made tests with this shield in place, not because of any intent
to endorse any particular brand, but beacuse I had one available. My
results with the shield exceed the manufacturer's promise of 50% reduction
in emitted power. With the ear-piece shielded and the probe centered on
the ear-piece and located 5 inches away from the phone, the radiation
power density was 37 microwatts per square centimeter.
Inverting the radiation density equation then gave power at the
surface of the shield of 0.075 watt. Thus, for this measurement, the shield
reduced the power emitted through the ear-piece to only 2.5% of the power
emitted by the unshielded ear-piece. This is remarkable and proves that the
manufacturers could make much safer phones than they do now!
I have had correspondence with the CEO of a company that supplies
parts for the wireless industry, and he has protested (to no avail) to the
FCC about how unrealistic the FCC requirements to test cell phones only in
the far-field are. He recognizes that the radiation environment in the
near field is far more complex than the FCC is concerned about, and he is
greatly concerned about the health implication of the near-field radiation
and believes that testing must be done in the near-field. Although I
won't mention his name or his company without permission, I can say that
he has been rebuffed by standard beaurocratic brush-offs by the FCC all
the way to the top. Even with the support of a letter from Senator John
McCain supporting his concerns, he has gotten no serious consideration of
his concern by the FCC.
Further, he has also been rebuffed by some people on the standards
setting commissions of IEEE and ANSI. He told me that he has sent out
many inquiry to the electrical engineering and bioelectromagnetics
communities, and my response to him - in the name of the EMR Network - was
the first time anyone had agreed to have a serious discussion with him.
Here is a qualified man (Ph.D. in, I suppose, electrical engineering and
head of a company that supplies components to the wireless industry) who
cannot get a serious response about testing from the people make and
enforce standards and test procedures that are based on those
test procedures and are supposed to guarantee public safety!
[!!!!!!...guru....]
In my conversation with this CEO I mentioned the work that the
Swiss Federal Institute of Technology has done in measureing the specific
absorbed dose of radiation (SAR) in simulated human heads and the fact
that their computer simulations also indicate that a large fraction of teh
overall radiated poer of a cell phone is absorbed in a user's head. He
told me that there are several ways that the industry could improve their
antennas to minimize the radiation emitted into the user's head. Cost is
the primary reason they haven't yet done this.
Bear with me in regard to the length of this letter. There is one
more point I would like to make. When my wife and I were waiting in the
AMTRAK station in New York City, a number of people near us used their
cell phones during the course of our wait. One of these people was a
young business man who sat about 10 feet away from us - almost opposite
us. He had one of the new, streamlined phones that have short antennas.
In this case, the antenna almost buried itself in his rather thick hair.
Whether because of this factor or because of the complex radiation
environment in the waiting room, my measured radiation density at 10 feet
away gave an extrapolated value at 6 inches from the phone that was
considerably more than what I had previously measured (crudely) on my
wife's phone at 6 inches in our motel rrom. (Unfortuantely, I didn't write
down either value and have forgotten them now.) Don't take this crude
result too literally, but I think the the new phones probably have to
put out more power than the older versions, because they have shorter
antennas. Of course antennas that operate at nearly 2 GHz would have to be
half as long as those that operate near 1 GHz, but this makes them more likely
to waste their energy in the user's head.
Roy L. Beavers wrote:
>
> ......A fellow physician provides support to Marj Lundquist,,,,,,,,,,
> "Science" amy call it an "anecdote," but it is fair to ask: why is
> "science" not pursuing (even if only to "disprove") the many anecdotes
> that are now known about the association of cancers or tumors in the
> vicinity of the ear that is used with the cell-phone???........
> (.....In memory of former Congressman Mike Synar.........)
>
> 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: Sat, 27 Mar 1999 02:00:11 EST
> From: Schillcj@aol.com
> To: rbeavers@llion.org
> Subject: Re: (Lundquist) An update on what I've been doing (fwd)
>
> This is interesting. I saw a man who had been acutely exposed to RF at 785 MHz
> with an area of erythema on his left chest, an arc eye type syndrome plus
> tenderness of the left temple, cheek bone, eyelid and ear. Four months after
> the exposure he developed a single solar keratosis on the left ear lobe about
> 5 mm in diameter. This was likely to have been in the area of maximum RF
> exposure. See my paper "Journal of Occupational and Environmental Medicine,
> April 1997, Vol54,No 4, p281 -284 Effects of acute exposure to UHF RF on three
> antenna engineers".
>
> Chris Schilling Occupational Physician
--
----
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 |
----------------------------------------------------
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