To be specific, when I worked for defense contractors I designed several cell-phone like frequency hopping systems along with being the project design engineer and Chief Engineer of a major ground-to-air military communications system for sold to Egypt and Harris RF devision in Rochester NY. This was before I went into the government and started working on ammunition and weapons systems.
I have personally used a cellphone at 37,000 feet while flying to the across the US towards the Carribean in a Lear Jet.
Any further questions about my capabilties? Oh, I have a BSEE with a Masters.
If you are a telecommunications engineer, why do you have to refer to someone else's article?
Now that we've cleared the air on capabilities, lets discuss the article.
According to AT&T spokesperson Alexa Graf, cellphones are not designed for calls from the high altitudes at which most airliners normally operate. It was, in her opinion, a "fluke" that so many calls reached their destinations.
"Spokesperson", probably a highly qualified double E.
The first sentence is absolutely true. If they were designed for use from airplanes, then there would be no need for a tower every few miles for line-of-sight communications. This would be slight over-kill.
Very much like a 1000 pound bomb was not designed for blowing stumps, but it would probably do the job with a slight amount of overkill.
Here is the statement of an experienced airline pilot: "The idea of being able to use a cellphone while flying is completely impractical. Once through about 10,000 feet, the thing is useless, since you are too high and moving too fast (and thus changing cells too rapidly) for the phone to provide a signal." (AVWeb, 1999)
Experienced "Airline" pilot, no doubt with a night job as an electronic engineer.
Actually, in the back of the plane, the cellphones signal would most likely exit the window and not radiate downward (same as the front of the plane). It would lock onto the first receiver obtaining a useful signal (just like it does on the ground). Since an airliner is up so HIGH, then think of it as a WUNDERFUL tower for line-of-sight communications.
The phone would no-doubt remain locked onto the same cell for quite a while, unless it just happened to catch that cell as it went over the horizon.
People boarding aircraft for the last decade or so have all heard the warnings to turn off their cellphones for the duration of the flight. The reasons for this regulation are somewhat mysterious, since the usual explanation, that delicate aircraft electronics might be affected by cellphone signals, is cast somewhat in doubt by the fact that all avionics are shielded from stray electromagnetic radiation. (Spitzer 1987) On the other hand, the FCC had apparently requested that airlines make this rule, owing to the tendency for cell phone calls made from aircraft at lower altitudes to create "cascades" that may lead to breakdown of cellsite operations. (Fraizer 2002)
Bologna. Avionics are NOT shielded on an aircraft. I can give you case after case where unintentional radiation (as it is called-even from the little clock on your laptop) _---wait, let me ask you, how would it get into the avionics receivers? Oh well, I'll tell you, it will go right through the antenna.
The cellphone system would NOT go down. That is bologna from Oscar Myer. But, it would probably get into a tower a long way off and cause potential roaming problems and if everybody in planes were using them, then the channels would be mightily messed up across the country. But, the system wouldn't go down.
As I have pointed out elsewhere, cellphone calls from commercial aircraft much over 8000 feet are essentially impossible, while those below 8000 feet are highly unlikely down to about 2000, where they become merely unlikely. (Dewdney 2003) Moreover, even at the latter altitude (and below), the handoff problem appears. Any airliner at or below this altitude, flying at the normal speed of approximately 500 mph, would encounter the handoff problem (Dewdney 2003). An aircraft traveling at this speed would not be over the cellsite long enough to complete the electronic "handshake" (which takes several seconds to complete) before arriving over the next cellsite, when the call has to be handed off from the first cellsite to the next one. This also takes a few seconds, the result being, in the optimal case, a series of broken transmissions that must end, sooner or later, in failure.
Again, b-o-l-o-g-n-a. Written by a double-E no doubt. Actually, it would be within range of a cellphone for probably 15 minutes or longer. Remember, cellphones are LINE-OF-SIGHT. Whoever gets into an open tower will stay there until the tower hands them over to a stronger signal at another receiver. Towers just don't hand off when another tower gets a stronger signal. They hand-off when the signal level gets too low.
Have you ever used a cell phone and started getting a fringe signal with static? Turn you phone off and on again and it will usually lock into a closer tower. (If one is available) and from an airplane there will be plenty of cells available and open.
It must also be remarked that the alleged hijackers of the Cellphone Flight were remarkably lenient with their passengers, allowing some 13 calls. However, it would seem highly unlikely that hijackers would allow any phone calls for the simple reason that passengers could relay valuable positional and other information useful to authorities on the ground, thus putting the whole mission in jeopardy.
Obvious. The highjackers only had knives, even if the population believed they had guns. They holed themselves up and sprayed tear gas in the front. They took over the cockpit and locked it up. DUHHHH!
There is no need to discuss any more of the article because it is more expansion based on cell-phones not working at altitudes.
So, when you finish YOUR technical rebuttal, please provide me with your answer as to who, exactly family members were talking to while all of this highjacking took place? Were they someone the government was holding hostage on the ground in Washington?
Your turn........