Planes and Cell Phones

[widebody911]

http://www.nypress.com/print.cfm?content_id=10706

The cell phone bit is interesting, but the penatagon lawn abstract seems a bit cockeyed.

MIRACLES AND WONDERS Last week, USA Today reported a joint effort between Qualcomm and American Airlines' to allow passengers to make cellphone calls from aircraft in flight. According to the story, the satellite-based system employs a "Pico cell" to act as a small cellular tower.

"It worked great," gushed Monte Ford, American Airline's chief information officer. "I called the office. I called my wife. I called a friend in Paris. They all heard me great, and I could hear them loud and clear."

Before this new "Pico cell," it was nigh on impossible to make a call from a passenger aircraft in flight. Connection is impossible at altitudes over 8000 feet or speeds in excess of 230 mph.

Yet despite this, passengers Todd Beamer, Mark Bingham, Jeremy Glick and Edward Felt all managed to place calls from Flight 93 on the morning of September 11. Peter Hanson, en route to Disneyland with his wife and daughter, phoned his dad from Flight 175. Madeline Amy Sweeney, a flight attendant, made a very dramatic call from Flight 11 as it sped to the North Tower. Barbara Olson made two calls, collect, to her husband at his government office from Flight 77 as it made its way to the Pentagon.

Each call was initially reported as coming from a cellphone. Later, when skepticism reared its ugly head and the Grassy Knollers arrived, the narrative became fuzzy; it was suggested that $10-a-minute Airfones were involved. Olson was an easy candidate for Airfone (one doesn't call collect from a cell), but as the stories developed, Olson—and Felt—were said to have called from inside locked lavatories. No Airfone there.

In the very near future, numerous technological miracles and wonders will rise up out of the ashes of that terrible day, much the way the space program supposedly gave us Tang and Velcro. Satam Al-Suqami's indestructible passport, for one, is currently under the microscope in the Reverse Engineering Department at Area 51. My old passport was falling apart when I finally replaced it last year, just from spending 10 years in my pocket. His survived the destruction of the World Trade Center. I want one of those.

Likewise, professional bowlers could benefit from inquiries into whatever physical force brought about the collapse of WTC 7. And as a frequent flyer who finds long-term parking difficult and expensive, I'd like to know by what mechanism Mohammed Atta got to Portland, ME, where he was videotaped boarding a flight to Logan Airport in Boston. His rental car was found at Logan.

And last but not least, every suburban homeowner will want the miraculous PentaGrass. Whatever that lawn at the Pentagon is made out of, it sure is amazing stuff—it resists and repels fire, explosion, skid marks, aircraft debris, jet fuel, luggage and body parts. **** from your neighbor's dog won't stand a chance!

Who would've thought there'd be a silver lining even in the debris cloud made that Tuesday morning?

[VenezianBlau 87]

A.D.D. + journalism degree = this article

BTW, I enjoy your posts.

I was hoping you were addressing the cell phone/flight instruments issue. Talk show host Neil Boortz, a gen aviation pilot, surmises that lighting up hundreds of cell towers at once from a plane has more to do with the prohibition of use.

Bob

[BlueSkyJaunte]

I've seen better posts on Slashdot...doubt this guy has a journalism degree.

I'll concede the A.D.D. though.

[Dantilla]

I am a pilot, and called the FAA to get a straight answer. Can't use them because of the FCC.

So I called the FCC. Can't use them because of the FAA.

They both say it messes with the other guy's equipment.

[djmcmath]

Cell phones on airplanes sounds like a fantastic idea I'd love to get started on this idea right away I wonder if they work did you hear about -- Anybody want to go ride a bike?

[Aurel]

Wow, that`s a great explanation, Wayne. Now, how do you explain that sometimes, on my boat, only two miles from the shore, I cannot reach any tower with my cellphone, while a passenger in a plane flying 30000 feet over me would be able to place a call and reach many towers ? The cell phone is limited by its emitting power to reach the tower if it is too far, in both cases. I`d like to see some serious references backing up your explanation.

Aurel

[Dantilla]

I specifically asked the FCC guy about the multiple tower thing. He just said that it messes with the airplanes avionics, and that's why it's a no-no.

If I got somebody different on the phone, I may have gotten a different answer.

[304065]

Wow, that`s a great explanation, Wayne. Now, how do you explain that sometimes, on my boat, only two miles from the shore, I cannot reach any tower with my cellphone, while a passenger in a plane flying 30000 feet over me would be able to place a call and reach many towers ? The cell phone is limited by its emitting power to reach the tower if it is too far, in both cases. I`d like to see some serious references backing up your explanation.

For all your leftist beliefs, certain aspects of PURE science are immutable (despite the perversion of "Social Sciences."

It's called "Line-of-sight," and based on simple geometry.

Mobile phones operate in the UHF frequency range. As such, UHF radio waves are "line of sight" and do not bounce off the upper atmosphere, they cannot reflect over the horizon like shortwave or AM radio.

As such, you can only expect a connection within the "line of sight" of the cell tower. Anything in the way (buildings, or terrain features) will block reception, also.

Consider the attached diagram. Standing on the earth (small red line) you can only transmit to the visible horizon which can be thought of as a circle drawn on the sphere of the earth at a point tangent to the line beween the position of the transmitter and the surface of the earth. The higher up you go, the larger that circle becomes-- you have "line of sight" to many more towers because you aren't blocked by the curvature of the earth.

Consider also that the max radiated power from most digital cellphones is only like .8 watts or less. Propogation conditions in the atmosphere vary widely but you aren't shooting that far with low power-- becomes hard to distinguish the signal from the noise.

[jm951]

Cell phones are an outgrowth of amateur radio technology of repeaters, UHF, VHF and offset freq use. The line of sight in the last post is correct. From high up, you can "see" repeaters (cell towers) from much farther than from a boat (0 ft above sea level). In the past, I've taken a 5 watt 2m rig, supposedly only good for about 20 miles, depending on line of sight, and keyed up repeaters from as far way as 350+ miles. The way I did it was a combination of altitude and atmospheric conditions. The VHF stuff can propagate a long way under a condition called a troposhperic duct. It acts like a pipe in the sky for radio signals and add in being on top of a mountain, and presto, your dinky 5 watts goes a very long way. In my case, I was talking with other hams in Atlanta from the NC mountains near Virginia using a 5 watt 2m "walkie talkie" that should have only reached about 15 miles. So, the crap spewed by some of the conspiracy fans about cell phones and coverage is just that- crap.

[Porsche-O-Phile]

Thanks Wayne! That's absolutely true. I'm a pilot and my father-in-law is a wireless radio engineer (well, a V.P. now). When I posed this very same question to him a couple of years ago, the answer I got was virtually word-for-word what you said.

And is it just me, or does that original article deserve an award for "most third-grade-attention-span-written-article" by the Pulitzer society or something?

[motion]

So the FCC is worried about a few people in the air making cell calls, when there are a million on the ground doing the same thing? Doesn't seem like if even everyone in the air was on the phone and their calls were lighting 10 towers each that it would even make a dent, compared to the ground use.

[LeeH]

My wife says she can hear the "tick, tick, tick" of cell phone interference over her headset if someone has a phone on in flight. Last time she asked the flight attendant to make an announcement that "The captain has requested that you check your cell phones..." Three people turned them off.

[TerryBPP]

My girlfriend called me from her cell just before taking off. I could hear everything the pilot was say to the tower and could only hear a whisper from her. So there must be some interference.

[304065]

Lee, that is a VERY interesting anecdote.

Another reason cell phones should not be used on aircraft is the principle of the "local oscillator."

Maybe some of the radio engineers here can comment, but basically the local oscillator is a mini-transmitter in the radio, that mixes with the received frequencies, and then all other frequencies are stripped out, leaving the signal you want to tune in.

Depending on the spectrum and the location of the intermediate frequency, you could generate enough RF intereference to mess with the avionics.

Try it sometime-- tune in an AM radio to a strong signal near the bottom of the band. Then tune in another radio in close proximity to the first, exactly 455 KHz higher than the first radio. All hell should break loose.

[jm951]

Motion-
A cell phone in the air is going to light up way more than 10 towers. It's that line of sight thing since a ground based phone can see maybe 3 towers max. From 30k feet the line of sight is huge. We used to chat with a guy in the ANG who would take up a 2 watt radio on training missions. From southern GA, he could peg our local repeater 5x5 from an altitude of about 12k feet. IIRC the transmitters on Voyager and some of the other space missions aren't very powerful and yet we can still hear them way out into the solar system.

As for avionics interference, all radio antennae have a degree of what can best be described as a "dirty" signal. In other words, there is some RF transmitted off freq. It occurs on wavelengths that occur at a harmonic point to the antenna and wavelength in question. Depending on what freq your cell is operating at, you could well be interfering with the avionics to some degree something that might be undesirable from a pilot's pov.