Cell tower emissions

[Tom Johnson]

All:

AT&T is installing what will probably be a large cell phone antenna in a faux steeple on St. John's Methodist Church about 300 feet from our house.  Just for curiosity sake, I would like to measure the current status of various radiation types and then the post-operation of the tower. 

Does anyone have the equipment to do such measurements or any suggestions about how I might capture that data?

Thanks,
Tom
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[Bruce Sherwood]

You would need extremely sensitive equipment to measure this, but it's
easy to make a rough estimate.

Typical output power of cell tower is apparently about 10 watts (from
various web sources). The power output is very low because (1) a cell
tower is deliberately designed to serve a relatively small area so
that it only has to deal with a small number of conversations at any
one time and (2) cell phones, like radios, have very sensitive
receivers.

A crude approximation is to assume the power is radiated equally in
all directions, in which case the power per unit area drops like one
over the distance squared. (Actual antennas may shape the transmission
pattern to be more directed than this, but I'll ignore this
complication.)

From Google maps one sees that your home is about 120 meters (or about
300 feet, as you say) from the new cell phone tower, so the 10 watts
transmitted by the tower is spread over a sphere of area
4*pi*radius^2. Hence the power per square meter at your home is about

10 watts / (4 *pi *120^2 m^2) = 55 microwatts per square meter

For comparison, sunshine delivers to your home a few hundred watts per
square meter.

To put it another way, the power level at your home is that delivered
by a 10 watt light bulb that's placed 120 meters away.

I found this about power leakage from a microwave oven:

The US Food and Drug Administration (FDA) has a regulation on
microwave oven leakage. In Title 21 it states that the power density
limit from an operating microwave oven "shall not exceed 1 milliwatt
per square centimeter at any point 5 centimeters or more from the
external surface of the oven."

I note that 1 milliwatts per square centimeter translates to 10 watts
per square meter, to compare with the estimated 0.000055 watts per
square meter from the cell tower.

Another comparison to make is TV. I assume there's a TV transmitting
antenna above the local ski area, about 20 km from your home, and it
probably radiates about 100,000 watts. The power per square meter at
your home is about

100,000 watts / (4 * pi * 20000^2 m^2) = 20 microwatts per square meter

So the power from the TV station is roughly comparable to the power
from the cell tower.

For more on electromagnetic radiation, see the video available on my home page:

http://www4.ncsu.edu/~basherwo

Bruce

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[Tom Johnson]

Thanks for the good info, Bruce.  And your house isn't that much farther than mine -- perhaps 600 feet?

But is the power always limited to 10 watts?  It turns out that the church is on or close to one of the highest points of elevation in this part of town.  And At&T has a notoriously low signal in most of Santa Fe.  So couldn't it just boast the signal strength to get greater coverage per tower cost, something like a radio station with 500 watts has a smaller signal footprint than one with 25K watts.

I wonder where the other AT&T towers are in town?

-tom

[Stewart Dickson]

I remember radio engineers doing field surveys with field-strength meters.  In those days, however, the frequency was in kilohertz, not gigahertz, but the principle is the same.   I know that there is at least one guy still in Champaign, IL who drives around with crazy yagi antennas up on masts on top of his car.   Got to be a field-strength surveyor.   Find a radio engineer.

[Steve Ross]

The antenna array on the tower is likely to be segmented, with one 10-watt antenna aimed in your direction. The lobe-shaped radiation envelope's falloff will depend on the number of segments. So you can assume higher than .055 milliwatt/m2 (.0000055 milliwatt/cm2) flux. Say it is about 10 times more (rough estimate because segmented antennas now often have 8 to 12 lobes). Still not very much. 

Steve Ross

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[Bruce Sherwood]

From http://en.wikipedia.org/wiki/Cell_site: The U.S. government
agency, the FCC, says: "For example, measurement data obtained from
various sources have consistently indicated that "worst-case"
ground-level power densities near typical cellular towers are on the
order of 1 µW/cm2 or less (usually significantly less)".

This 1 microwatt per square centimeter is 10 microwatts per square
meter, lower than my estimate for the power density at your home.

From http://en.wikipedia.org/wiki/Mobile_phone_radiation_and_health (a
site which also has some discussion of cell phone tower regulations):
Because base stations operate at less than 100 watts, the radiation at
ground level is much weaker than a cell phone due to the power
relationship appropriate for that design of antenna.

In other words, I think it's the case that emissions from cell phone
towers are very low, by design. They are certainly vastly smaller than
what is radiated by your own cell phone held near you.

My impression of the literature on these matters is that if you do a
million studies you will by chance find quite a few studies that
demonstrate terrible effects of cell phone towers. The same would be
true if you did a million studies of anything else. I remember a
lovely question, probably in the 1980s, which asked, "Have you noticed
how badly things have gone in the world since people started saying,
'Have a nice day'?"

Bruce

[Steve Ross]

1 microwatt per cm2 is 10000 microwatts per m2 or 10 milliwatts, but that is worst case. It is also pretty low low but far higher than my calculation of .055 milliwatt/m2 (which is, of course, for 300 feet away).

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[Fabio Carrera]

We conducted a project in Venice on "Cellular Bell Towers" in the late 90's, early 2000's.

As I recall, one should worry more about the emissions from the phone than from the towers...

F

                                                                            

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On Mon, Aug 6, 2012 at 11:16 AM, Bruce Sherwood <bruce.s...@gmail.com> wrote:

[Steve Smith]

Here is my reasoning (it is probably somewhat limited and even flawed, building off of other comments here, but a good start I hope):

1. Asymmetry:  The threat of cell towers vs cell phones to the individual (using a phone) is asymmetric.  Cell phones themselves generate a watt or two of rf emission....  in you pocket  the flux to your brain is on the order of .5-1 w/m^2  and then when against your face it goes up by a factor of 100 or so.  Remember that your *phone* has to reach the tower just as much as the tower has to reach your phone, and *it* cannot afford as directional of an antenna as the tower can.
   
2. Adaptive Power Strategies:  Since phones adjust their power emission based on how good of signal the tower gets from them (this is negotiated),  having a good cell tower signal reduces the threat from your own handset.  A net gain.   What is the collective flux of an elevator filled with blackberries in hip holsters striving madly to reach their towers through the weak faraday cage that elevators seem to be?  Forget tinfoil hats, I'm going for the tinfoil jockstrap.
3. Choice:  For those who choose not to own or use cell phones (for any of many reasons), they do not have a choice about being irradiated by cell tower signals (except to live far from civilization).  But same for all environmental pollutants.
   
4. Human Health: Not all emitted electromagnetic energy is the same when it comes to human health...
   
1. Bruce's note of the radiative flux of the sun describes EM almost entirely in the visible light spectrum.  Of course, anyone who has spent an hour or two in the unprotected sun knows about radiation (sun) burns to the skin.
   
2. Microwaves are *designed* to couple with water molecules, so, leaky microwaves are going to heat your organs just like they do your kidney pie.  Apparently the biggest threat is to the cornea because it has no circulation to cool it?   Leaky microwaves lead to early cataract formation?
   
3. I'm not sure anyone has good data on the various forms of communications spectra and health... whether radio, TV, wifi, cell towers, or wireless phone handsets, or wireless thermometers or car remotes or bluetooth headsets themselves (worn by design in your ear?).
4. Those who study such things seem to be more concerned about something called "specific absorption rate" or SAR measured in W/Kg and applied (apparently) to the head only... with limits up to 2 W/Kg.  Details of how this is measured is not immediately evident, but I'm guessing it is strictly in the context of holding one's cell phone against the side of one's head, not living a few hundred meters from a tower, or even standing under it.
5. Power Distribution:   People have been worrying about high power (and even house current) as a source of EM for decades... and it is a lot closer to us (how many power cords snake behind the headboard of your bed, or in the wiring of your walls?)  OK... maybe 60 hz radiation isn't a threat?  But what is the flux of *that* radiation?  And those high Tension wires (measured in kEV s?) running over the landscape?
   
6. Other devices:  our own wireless routers, cordless handsets/base stations, wireless remote thermometers, vehicle remotes, etc.  We have *bathed* ourselves in synthetic EM across a wide range of frequencies and power levels... so it doesn't surprise me that some folks are very worried... but my feeling is we should be worried about *all* of it, not the more evident or obvious things.  Remember when lots of people believed the government was "beaming messages into their heads"?
7. Dowsing for Spectra:  With Santa Fe's propensity for worrying about and/or believing all kinds of things, I think a fancy van with a bunch of antennae sprouting from it driven by a guy in robes with a wizard's peaked hat made of tinfoil waving a Yagi antennae around like a dowsing rod could probably make a pretty good living doing "surveys".   Similarly, a real radio engineer could do the same with a real power analyzer.... but I assume no self-respecting radio engineer is going to give over to the presumption that any of our communications systems are a real threat to anyone.  Hindsight may inform us that some of this IS dangerous but I think the negligence leading to that will be more subtle than gross.
   

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[Nicholas Thompson]

Bruce wrote:

 

I remember a lovely question, probably in the 1980s, which asked, "Have you noticed how badly things have gone in the world since people started saying, 'Have a nice day'?"

 

Now wait a minute!  That IS a causal relation.  That and “No problem!” presumably responsible for everything that has happened in the last 20 years, including terrorism and Global Warming.

 

Nick

--

[Bruce Sherwood]

Thanks for catching my error. Right -- 10 milliwatts per square meter
right next to the tower.

Bruce

[Bruce Sherwood]

The visible part of the sun's spectrum doesn't burn the skin; it's
only the ultraviolet component (mostly blocked by the ozone layer,
fortunately). Note that in the photon picture, UV photons are higher
energy than the visible-light photons, and all radio/TV/microwave etc.
photons are very low energy.

Bruce

[Steve Smith]

 
<$300 via Amazon
Add Tinfoil Hat and Yagi antennae
on your Subaru covered in bumper stickers
and you have an instant business
"dowsing" for EM in Santa Fe.

Retraction: My reasoning below had at least one glaring flaw...

2.   Cell phone transmit strength would not be correlated with cell tower power, but rather it's receiving antennae configuration and tuning as well as environmental (obstructions, etc) conditions.

[Steve Smith]

Bruce -

The visible part of the sun's spectrum doesn't burn the skin; it's
only the ultraviolet component (mostly blocked by the ozone layer,
fortunately). Note that in the photon picture, UV photons are higher
energy than the visible-light photons, and all radio/TV/microwave etc.
photons are very low energy.

Good point, I could have added that to my retraction as well.. Though
the offending UV (that gets through the atmosphere) isn't *that* far
from visible light. It is a question of coupling as much as energy,
right? My point (I suppose) was that we accept a very known risk from
radiative energy *all the time* that is more immediate (if not more
dire?) than cell phone and wifi signals.

In 2000 I spent 10 minutes at sea level in New Zealand getting a sunburn
against *all my intuition* having lived at 7000 feet most of my life and
knowing to cover up for 30-60 minute exposures as a matter of course.
The daily news there gave a report on the disposition of the rotating
ozone hole at the time, and despite my background in physics, it was
just too hard for me to take in, until I fried myself in 10 minutes in
the sun! Makes one feel very vulnerable.

I understand that we (the industrialized peoples of the world) actually
turned *that* anthropogenic disaster waiting to happen around with only
a modest amount of effort. I use this anecdote with my
"climate-change-denier" friends. If we could *actually* mess up the
ozone layer with 50 years of CFCs and other ozone eaters and then *undo*
it in another 20 or so, then ignoring/denying our greenhouse gas problem
is ridiculous (insane?). We clearly have more reach than we think,
both to unbalance nature and to undo/stop (some of?) our unbalancing.

On that note, I'm sympathetic with the EM emission worriers, even if I
think their facts are wrong or wildly exaggerated.

- Steve

>
> Bruce
>
> On Mon, Aug 6, 2012 at 10:50 AM, Steve Smith <s...@lava3d.com> wrote:
>> Bruce's note of the radiative flux of the sun describes EM almost entirely
>> in the visible light spectrum. Of course, anyone who has spent an hour or
>> two in the unprotected sun knows about radiation (sun) burns to the skin.

[Steve Ross]

At Tom's suggestion, I wrote a piece on this for the Journal back in 2008. It is still on line at

http://www.abqjournal.com/north/opinion/310409northoped06-08-08.htm 

While I see absolutely no measurable risk from the cell tower close to his home (or from the antennas close to my home), I'm a bit surprised that AT&T, as part of its application to build the tower, is not required to calculate and provide a flux density contour map. 

There is a real but unlikely danger -- some medical monitoring equipment, especially older equipment often used in small medical practices or at home, can be addled by cellular signals, both at the normal frequency (about 1.9 GHz), from the new cellular band at 700 MHz, and from harmonics.

BTW, it is likely that the new cell tower will be served by a fiber trunk. That means Tom would not be very far from some bigtime bandwidth, if he could take advantage of it. Would have been nice to be able to negotiate a good connect rate from AT&T for the neighborhood BEFORE they got permission to build.

Steve

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[Bruce Sherwood]

Nice article, Steve.

Bruce

[Chuck Baldwin]

"fiber trunk",

If you mean optical fiber, there is not a flux field present.

-C

[Steve Smith]

Good article Steve...  and good point about the implied issues with Cell Tower locations/franchises/bandwidth access.

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LAVA-Synergy
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505-920-0252

[Steve Ross]

I don't want him to fear the fiber, I want him and his neighbors to be able to take advantage of it for their landlines. Usual thing is for at&t to lease dark fiber as far as they can and create a PoP (hub) to tap into for the spur to the tower. The tower base has another PoP. Either one could be place to base a little network.

(sent from mobile phone)
Steve Ross
+1 201-456-5933 mobile
+1 781-284-8810 landline
"editorsteve" on Facebook & LinkedIn

[Tom Johnson]

I guess, then, I shall have to throw myself in front of the AT&T trucks until the company agrees to give the neighborhood a direct link to its trunk-line fiber. 

Damn, and to think I was going to have a relatively quiet week.

-tj

[Nicholas Thompson]

Would anybody be willing to take a few sentences to explain to me why photons DON’T have flux? 

 

Thanks,

 

 

Nick

 

From: Steve Ross [mailto:edito...@gmail.com]
Sent: Monday, August 06, 2012 3:05 PM
To: dis...@sfcomplex.org
Subject: Re: [sfx: Discuss] Cell tower emissions

 

I don't want him to fear the fiber, I want him and his neighbors to be able to take advantage of it for their landlines. Usual thing is for at&t to lease dark fiber as far as they can and create a PoP (hub) to tap into for the spur to the tower. The tower base has another PoP. Either one could be place to base a little network.

[Chuck Baldwin]

I might be stating it incorrectly. An arc welder or any copper pair with electricity passing through it has an electromagnetic flux field around it.

You aren't going to find that around an optical fiber.

-C

[Nicholas Thompson]

Right.  Got that part.  But why?  It’s all electromagnetic energy, right?  Or is that EXACTLY where I am screwed up.   It’s possible the question is just too inane to be worthy of an answer.  Nick

[Steve Ross]

The short answer is that a variable electric current produces a magnetic field and vice versa, but the photon is the "field" and in a nonconducting medium doesn't induce the current. The typical EE however would say that the math is different.... Radio waves are Faraday thingies and photons are quantum thingies.

Sayeth the physicist: No flux outside the fiber until the photon flow is enough to quantum-couple with electrons in the glass. You need millions of visible-light photon energy levels (wavelengths)  all in the glass at the same time to do that or you need much more energetic photons than the visible light range (or any existing pulse lasers) provide. Or you need a glass "doped" with something that has electrons easy to excite away... but that wouldn't make a good transmission medium, would it?

(sent from mobile phone)
Steve Ross
+1 201-456-5933 mobile
+1 781-284-8810 landline
"editorsteve" on Facebook & LinkedIn

[Chuck Baldwin]

I leave this to the real physicists. But I think the answer is where "light" resides in wavelength in the EMR spectrum. Which dictates it's interactivity with atoms and molecules, or lack thereof. Thus creating or not creating an electron flux field.

-C

[Chuck Baldwin]

This is an interesting idea. If you had a fiber whose cross section was a tube within a tube within a tube, and each layer alternated between clear and doped, there might be some kind of resulting application out of that configuration. The partial interaction at the interface between layers could have some kind of function, and the doped layer as well, and act to siphon off or in some other way mollify or modify the photons in the clear layers. Or any variation on that theme.

-C

[Chuck Baldwin]

maybe I'm caught in a loop here and not going anywhere...

-C

[Steve Smith]

Nick -

Good question as usual.   One way of looking at is that an optical fiber is an ideal waveguide for Electromagnetic Energy (within a limited spectral range, usually visible light or nearby). 

If it is, in fact, Ideal, there will be no emanations or escaping energy (electromagnetic flux being a measure of power per area or energy over time per area).  

Aside from this making fiber optics a good communication medium because it is lossless it is also hard to "listen in".  A few tricky folks have done things like given a fiber a real tight bend to *cause* the fiber to become less ideal and leak a few photons to "read".  There are also "optical taps" which are essentially beam splitters that can be put inline with optical fibers to passively pull out a signal without being (too) obvious... of course the signal split out is energy (and information) not going on through the fiber... so the other end can know that something is missing, and of course, you have to cut the fiber to insert it... and there are some reflections that are returned with every end/element... if/when not ideal.

As indicated, when electric currents are flowing (in wires), the wires themselves emit electromagnetic radiation.  When this is done on purpose, we call them antennae, when it is unintentional we call it line loss (along with resistive losses).

The discussion at hand is mostly about the *intentional* EM radiation coming out of antennae... and the point being made is that Fiber Optic (waveguides) are losing virtually nothing and therefore radiating virtually nothing... and even if they did it would be in or close to the visible spectrum, not one of the "nasty" spectra that people might be worried about.

Clear as (more) mud?

- Steve

[Nicholas Thompson]

Thanks, steve.  That is very helpful.  Nick

--

[Chuck Baldwin]

ow.

http://www.woohome.com/electronics/nokia-gun-mobile-phone 

-C

On Sunday, August 5, 2012 7:20:46 PM UTC-4, Tom Johnson wrote:

All:

AT&T is installing what will probably be a large cell phone antenna in a faux steeple on St. John's Methodist Church about 300 feet from our house.  Just for curiosity sake, I would like to measure the current status of various radiation types and then the post-operation of the tower. 

Does anyone have the equipment to do such measurements or any suggestions about how I might capture that data?

Thanks,
Tom

[Steve Ross]

Definitely not a smart phone...

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[Arlo Barnes]

When mentioning this discussion with my mother, she pointed out that, as a kind of counterpoint to the name of the organisation WhyFry Santa Fe, it is too bad this thread was not on the FriAm (Fry 'em) list.
-Arlo James Barnes

[Chuck Baldwin]

http://phys.org/news/2012-11-fundamental-electromagnetism.html

-C