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If folks were truly concerned about the dangers of cell phones, then their use would be banned while driving. I've read cell phone use causes more accidents than drunk driving.

I second JoAnne's statement. Just last week I saw a driver totally ignore the cop who was giving directions at an intersection while the lights were down because the driver was preoccupied with his cellphone conversation. The lack of consideration for others' safety is much more dangerous than any long-term effects from the electromagnetic fields used in mobile phones.

I agree with the previous comment on driving and cell phones. I've been nearly hit several times by oblivious idiots chatting on their phones.

The "Mythbusters" tested whether a cell phone could interfere with avionics. As I remember, their conclusion was that it was plausible. I suspect cell phones are more of a potential problem than GPS is that the transmitter is closer to the avionics and presents a stronger signal. I believe the GPS signal is also spread over a wider bandwidth.

There isn't a 111 MHz gap between cell phone frequencies and air traffic frequencies. There are other services using it. There are also other cell phone frequencies around 1900 MHz. Here's another web site that lists frequency allocations:

Another problem with mobile phones which might happen on aircraft is that if the phone can't get a response from the network, it electronically shouts louder and Louder and LOUDER until it does get a response. An aircraft full of phones none of which can hear any base stations would be a *very* noisy electromagnetic environment indeed, far more so than the piddling little signal from GPS.

Another issue with phones on planes is with how they'd interact with the base stations on the ground. They're designed so that you'll never "see" more than a tiny number at once, and not change cells particularly fast. If you're on a plane travelling at umpty hundred miles an hour at tens of thousands of feet, then if you do get a signal you'll get it from a *lot* of cells, and cells will move in and out of range very fast. The network doesn't like that at all.

And finally, remember that take-off and landing are the most dangerous parts of a flight. That's why you're asked to turn off games and computers - when you turn them off you generally put them away, so in a crash they won't go flying around the passenger cabin and injure people. Of course, the airlines don't like to tell people the real reason so spin a tale about interference.

Cellphones seem to always talk to speakers, computer or otherwise, as far as I've found. It seems to occur when the phone is first turned on, and when there's about to be an incoming call. I think it's when the phone is exchanging a 'handshake' with the nearest cell tower, acknowledging the phone's existence or seeking it out to relay a call. The system doesn't even have to be powered on, as I've intercepted the 'dup de dup de dup' buzzing pattern on a stereo that's turned off (though plugged in).

In fact, it works so well that I'm seriously considering setting up speaker circuits around my classroom in order to pinpoint the cellphone offenders who try to text unseen...

The "no cell phones on airplanes" rule wasn't (just) about interference in the spectrum. There are also FCC regulations in place because the use of cell phones that far up could confound cell towers and interfere with ground based communication (or at least they could when the rule went into place in 1999).

The other, non-scientific, explanation is that business traveler values the peace and quiet of three blissful hours away from their cell phone (and don't really want to listen to 50 other passengers screaming over each other into their own phones).

There was a nice (and humorous) article in The Economist a while back (Fear of flying, Sept 7th, 2006 (sub req.)) about lies during the safety instructions.

Also, the annoying signal from the mobile phone comes from the phone switching on and off with a ~217 Hz frequency for bandwidth sharing. This bandwith sharing causes a lot of noise in the audiable frequencies that can be picked up by the loudspeakers.

When it comes to interference phenomena, a Swedish blogger recently complained in a post that switching of his ceiling lamp changed the channel on his TV.

I once put a compact fluorescent into the ceiling fixture in my living room. It continuously simulated the "Volume Up" function of the infrared remote for my stereo. I removed the compact fluorescent from the ceiling fixture in my living room.

Hi, you can use mobile phones on Ryan Air
Of course you'll be hampered by the limits of your mobile phone - and there is always the risk that a savvy terrorist could alter his mobile to interfere with flight control (especially during take off or landing) - oh no, I shouldn't have said that, they are sure to ban mobile phones in the air (again). But the Ryan Air boss is a pretty cavallier chap, no fear of mobile phone terrorism on Ryan Air flights, more likely to get - having to queue for a pee - air-rage.

And I agree with JoAnne, car drivers on the ground holding a cell phone instead of the steering wheel pose a more serious threat - if you must talk to someone other than the person next to you, please use a no hands mobile phone in your car. Thank you!

The National Telecommunication and Information Administration (NITA) has an excellent pdf document showing just how crowded the frequency spectrum really is. I keep a large poster of it in my high school physics classroom. Go to NITA at: and click the "U.S. Frequency Allocation Chart as of October 2003 (Adobe Acrobat format)"
This poster explains why telecommunication companies are paying $billions for a slice of the UHF, SHF, and EHF pie.
This will all get very interesting as NASA is predicting a VERY active solar cycle 24, due to peak in 2010/2011.
We have a very "boring" sun right now as the 11-year sunspot cycle bottoms out in late '06/early '07, but as we ramp up in activity over the next 5 years, Mother Nature might be the one opening garage doors.

All electronic devices leak - phones at frequencies above and below the transmission frequency - they are effectively computers with clock pulses and and data buses and carrier waves and lots of other stuff. Earlier phones, I can't recall whether digital or analog, have been shown to interfere with Autopilots and other navigational equipment. Among the reported symptoms were errors in altitude and heading, both pretty serious. Of course newer phones try to save power, so if they can find a base station, they don't use as much power and there is less risk.
I do suspect that human engineering is going on as well. If you want humans to do some things, they won't do it if you give the real reason, but if you give plausible reasons which can have an impact on EVERYONE in the plane, most will go along.

If we were serious about safety, we'd outlaw cars altogether. Americans have a one percent chance of death due to an automotive accident.

I doubt that the driver with a cell phone is more dangerous than the drunk driver. But, there are many more cell phone drivers out there.

The number of drunk drivers out there is likely under reported. Not all of them have accidents.

The MIR space station is not likely to be transmitting any time soon.

The chances of one device sending another device a command code can be reduced by having more complicated command codes. My garage door remote doesn't open my neighbor's doors. But, i'd bet that if i tried other neighborhoods, i'd eventually open a door...

There's also another ominous form of sound waves afflicting parts of New York, which are being used to chase occupants out of their apartments so landlords can hike rents. It's a rather odd device - a test pattern generator/oscillator coupled with an operating system that works like audio radar that can track the movement of occupants through concrete walls and specifically target their ears with a stream of 9,000 MHz sound. Briefly, the intense sound waves are beamed through floors or ceilings by a series of small sensors strategically mounted on the wall, ceiling or floor. The stream works like motion detection equipment. Once the signal bounces off a moving object, it returns to the sensors. The PC then, gradually, via triangulation, gets a read on the location of the target and projects a steady stream of nearly invisble sound (you have to hear it to believe it!) that in turn follows the occupant throughout the apartment. The powerful stream, nearly inaudible unless it's directly aimed at the ear, can in due course cause deafness.

The system apparently originated in North or South Korea by a firm called, Yoon, inc. If you're assaulted by such a device, vacate immediately.

Personally, I'm far more concerned about the affects that all of these devices are having / will have on radio astronomy than I am with the minor inconvenience of one device talking to another (although they're caused by the same thing - normally crossover into a frequency they're not supposed to be in). See and for more info.

Concering the relative interference of GPS vs cell phones:

The big difference is that while cell phones transmit RF, GPS devices are "listen only". The transmitters in a GPS net are all in satellites, so the power levels at the receiver end is really, really low. As a matter of fact, GPS power levels are actually below the noise floor of any practical receiver and require clever signal processing for the receiver to function. Cell phones, on the other hand, transmit tens of milliwatts when you're talking, and are obviously very close to the aircraft receivers. So interference is much more of a problem for cell phones.

Thats nice to share the views every one here. Get more info about what medical physicians around the world are saying about the effects of cell phones and electromagnetic frequencies.For more information

Also, don't forget: airlines don't want you to use your cell phone for no charge when they can make you use an airfone @ several dollars a minute...

About what Alan was saying in the above post...
Even the older garage door remotes that use dip switches are relatively secure against random guessing as 2^8 is a very large number.

"Tools for Healing" ... A long time ago a friend and I were thinking of selling "Radioactive Electron Filters" that you could plug into the wall socket. The idea was that it would filter out those "radioactive electrons" produced by nuclear power plants.

I guess we just weren't in the same league as these other guys.

"... the strange voices being emitted from my computer speakers ..." I'm waiting for the late-night talk shows to pick up on the "space aliens are taking over my computer" thread.

Not only that, but "carbon dioxide is a dangerous substance" that will have be be regulated.

"... specifically target their ears with a stream of 9,000 MHz sound." That sounds a lot like the system invented by Woody Norris:

Woody Norris, HyperSound

Norris is better known among the industrial community as Elwood Norris - at least, that's what it says on his Lemelson-MIT Prize. His system (one of his many inventions) lets you send out an essentially coherent beam of sound, over long distances (a few hundred meters). One of the applications has been used to repel pirate boarders from a Navy ship. The system doesn't just send noise, it sends voice and music.

The downside of the system is that "they" will be able to direct targeted commercials to individual people (or groups) is places like Times Square. And the voices will be coming from inside your ears, not a remote speaker.

"Isn't the GPS a far greater interference risk, or am I missing some crucial point?"

As Jim pointed out, GPS are receive-only, so they don't emit anything. However, some countries do ban them, on the assumption that anyone who wants to know where he is in the air must be planning on taking the plane to somewhere other than its scheduled destination.

Thanks for the re-post! Like Quasar9 I use the poster of the U.S. Frequency Allocation chart when I teach high school physics. I also have my overhead fluorescent light occasionally turn on my TV/DVD player to DVD mode. I may point my students to this blog post when that topic comes around again this year.

I came across this while working on my thesis in robotics. I have a wireless camera installed on the robot, than when being used interferes with the wireless network. Which was a pain since I couldn't look up anything on the internet, send emails, etc. while the robot and camera were in operation. Occasionally it also seemed to interfere with the bluetooth that I was using to communicate with the robot from the PC. Though fortunately this was infrequent, possibly due to the "hopping" bluetooth uses.

On another note, you mention the web site How Stuff Works. The founder of How Stuff Works, Marshall Brain, was an undergraduate teacher of mine, many moons ago. He was fantastic in explaining things such as doubly linked lists and binary search in an early programming class. He is also giving a talk entitled "The accidental entrepreneur" at NCSU (, which I am planning on attending.

Thanks for the great blog, keep it up!


P.S. - I bought "Physics of the Buffyverse" for my fiance. So far she's enjoying it.

I do remember a study reported by someone - I can't remember any details, so it's hearsay to you ... :-)
It showed that the leakage from Cell Phones could interfere with the altimeter and other guidance systems. If this happened in an airliner, then an incident like on Qantas 737 in Aus a few weeks ago could happen - it appears the altimeter told the Autopilot that the plane was several hundred meters too high, so the plane dived suddenly and many people were injured because they weren't in their seat belts ...
If it happened at night in the Rockies ... the plane might hit a mountain !

Any Radio transmitter leaks other frequencies and lots of receivers use Phased Locked loops which means the receiver generates some of the frequency that it is trying to receive and actually leaks other frequencies too !
This is how Radar Detector Detectors work ... by detecting the leakage from the PLL in the receiver.

I certainly have to agree with the Quietness reason on planes - I DO NOT want to listen to any business man's whinges for a constant three hours on a plane !

I wish phones were totally banned while driving - my kids would rather I make it home on my motorcycle or bicycle than have someone wipe me out while discussing what colour shoes they're going to wear tonight !

Two slogans I have thought of ...

Hands Free or Hands Off

If it's important enough to answer, it's important enough to pull over !

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