Airlines ban cell phones -- but why?

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cell phones on aircraft...

I ahve been in the industry (cell pohnes) working as an engineer for over 15 years.

This is a response (by me) of an email i recieved about the possibilty of using cell pohnes in aircraft.

the original email referenced this article...
http://www.physics911.net/projectachilles.htm
a test conduted showed that cell phones have a VERY low precentage rate of connection above 5 to 7,000 ft.

I concur

Here is my reply...

========================================

my analysis on cell phones and 9-11
http://911review.org/brad.com/sept11_cell-phones/engineer_tech.html

engineering and technical discussion about the use of cell phones on planes.
http://911review.org/brad.com/sept11_cell-phones/physics911_discussion.html
http://911review.org/brad.com/sept11_cell-phones/physics911_discussion2.html


One call was supposedly recieved in Illinois ?!
http://911review.org/brad.com/sept11_cell-phones/illinois_flight-93.html
http://physics911.ca/org/modules/weblog/details.php?blog_id=65


other links...
http://911review.org/Wiki/CellPhoneCalls.shtml
http://911review.org/Wiki/CellPhoneCallsFlight77.shtml


> As this is your advertised area of expertise, I'd like your
> comments regarding this aspect of the 9/11 investigation. The
> official story of Flight 93 was that someone was able to make a
> call on his cell from a bathroom from six miles in the air whilst
> flying at ~500 knots, which never made a lot of sense on the face
> of it -- I know how persnickety my new cell is! The author, a
> professor of mathematics at the University of Waterloo in Ontario,
> extrapolating from empirical evidence, calculated that the
> probability of making a cellphone call to the ground from a jet
> plane flying at that speed and altitude using circa 2000 cell
> technology was essentially zero.
>
> http://www.physics911.net/projectachilles.htm
>
> On that page, an apparent expert in cellphone engineering weighed in:
>
> Hi,
>
> I am an RF design engineer, having built out Sprint, Verizon and
> another network in New Orleans. You are absolutely correct. We
> have trouble making these things work for cars going 55 mph on the
> ground. If you need another engineer's testimony for any reason,
> let me know I will corroborate.
>
> my engineering site: http://www.geocities.com/rf_man_cdma/
>
> Brad Mayeux
>
> (I am taking the liberty of e-mailing Mr. Mayeux, in the hope
> that if you disagree with the professor's findings, that he would
> be kind enough to share his expertise, and debate you on the topic
> if need be.)
>
> Another comment from an engineer:
>
> Prof. Dewdney:
>
> I do not pretend to be any sort of expert of cellular communications,
> but I am an electronics engineer and hold both amateur and commercial
> FCC licenses, so I do have some understanding of the relevant
> principles of radio communication systems.
>
> I read with interest your analysis of terrestrial contact
> probabilities via cellphones from aircraft. I believe your conclusions
> are sound, but would like to comment on an element which you pondered
> regarding the sort of apparent discontinuity in what seems otherwise
> to be an inverse-square relation beyond a certain altitude.
>
> Cellphones operate by Frequency Modulation, and as such the (apparent)
> signal strength is not discernible to the listener because the
> intelligence is contained only in the frequency and phase information
> of the signal before demodulation. Hence, the system works pretty well
> until it is so weak that it is abruptly lost. That is, the system can
> no longer "capture" the signal. It does not get louder and softer with
> signal strength -until the signal is below the detection level of the
> receiver, at which point it is essentially disappears.


Most cell phones today (and most, but not all in 2001)
used CDMA technology.
In CDMA, all calls are on the same frequency.
(per carrier)
they are coded and decoded individually.
each call has a unique PN number
Each of these are "time delayed" offset by a certian amount.

it is like being in a room with 10 conversations going on in different languages.
if they were all in english, then it would be confusing, but not so with different languages.


> The cellphone
> also adjusts the transmit power according to the signal level received
> at the tower end of the link. Once it is at maximum output, if the
> signal diminishes beyond some minimum threshold depending on the
> receiver design, it is lost altogether and not simply degraded in
> quality. Analogous behavior is experienced with FM broadcast stations;
> as you travel away from the transmitter the station is received with
> good fidelity until at some distance it rather suddenly cannot even be
> received any longer at all.


True,
but noise levels work a bit differently in CDMA.
since everyone is on the same frequency, noise is a problem.
the more users, the more noise, (the higher the noise floor)
the phone and the base station both send each other information
as to when to power up, and how much to power up (or down)
according o the ammount of noise.

>
> Additionally, cellphone towers are certainly not optimally designed
> for skyward radiation patterns. Since almost all subscribers are
> terrestrial that is where the energy is directed, at low angles.
>


Very true.
often we point the antenna downward a few degrees (downtilt)
additionaly, the base stations antennas are usually 33 to 65 degrees.,
and the power drops considerably on the edges, the farther away you are
(rolloff)

ALso,, i have tried making calls from airplanes during travell
(shhh...)
my experience was similar to Kee's results,
even when there was a connection, and when i had service (signal)
the call would not last more than 2-3 seconds (over about 7,000 ft)


> In summary, if your observed discontinuous behavior is real, and I
> believe there is technical reasoning for such, the probability of
> making calls beyond some threshold altitude is not simply predictably
> less, but truly impossible with conventional cellphones under any
> condition of aircraft etc. because of the theoretical limits of noise
> floor in the receiving systems. I think the plausibility of completing
> the calls from 30,000+ ft. is even much lower than might be expected
> from extrapolations of behavior at lower altitudes which you
> investigated.


Where flight 93 supposed calls came from was above 35,000ft or
more the most part according to the maps.
http://airgames.bravehost.com/Flight93.html


part of what i have found, is that the maps may not be accurate.
I noticed many 9-11 researchers take for granted the maps
of the planes flight paths on 9-11
There are several reasons i dont believe these are accurate.
One curiosity is that the transponders were turned off, then back on again
(supposedly)
on most of the flights, if not all.

Now, this makes NO SENSE for a hijacker to do,
all it would do is tell the world "here i am"
sending signals that there is a problem as well.

But, my take is that the air traffic controller may have either been mistaken,
or "duped".
the air traffic controller sees 2 types of signals to identify the plane.
Primary and Secondary radar.
http://www.airwaysmuseum.com/Surveillance.htm
Primary radar is just the reflection of a signal
Secondary radar is a signal sent by the plane from a "transponder"
the transponder is used to identify the plane.

From what i understand, the transponder signal can be changed.
ARINC is one company that has the ability to do that,
i have been researching material that sems to tell me
that there is a "superdatabase", central computer
that can be accessed (or hacked)
PTECH had the ability to do that (i think)
and was also under investigation by the FBI
recomended link...
http://911review.org/companies/MITRE/MITRE_Bollyn.html
other links...
http://911review.org/Sept11Wiki/Ptech.shtml
http://911review.org/Sept11Wiki/PrinceTurkiAlFaisalAlSaud.shtml
http://911review.org/Sept11Wiki/MitreCorporation.shtml

additionally, the guy who was responsible for telling us where the planes went on 9-11
(flight maps)
had deep ties with the DOD and also worked with war gaming software !
http://physics911.ca/org/modules/weblog/details.php?blog_id=58


In summary, the calls MAY have been real, but either were not made
at the altitude suggested, or, were from a different plane,
or, some, may have been faked altogether.

since there was war gaming going on...

http://911review.org/brad.com/batcave/WarGames.html
http://angie.911review.org/id8.html
http://911review.org/brad.com/wargames/computer_war-games2001-1.html

there is also the possibility of a "drill" phone call.

PILOT: Hi, this is your pilot speaking, please bear with us,
you will be part of a DRILL we are conducting !
(they pick 2-3 people)
please dial 911 on your cell phone,
dont worry, we have contacted the appropriate authorities
and let them know this is a drill.
they are working closely with us.

And the FAT OSAMA video is a total fake , i agree !
ive done some closeups myself.


Well, i certianly believe somethings up,
i very seriously doubt that these calls could have been made.
feel free to include me in any correspondence on this subject,

Brad Mayeux
http://www.911review.org

Posted by: 911review   Posted on: 07/14/06 You are currently: a Guest | Members login | Terms of Use

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