"... and please switch off all electronic devices."

[DawnFalcon]

...Completely unshielded speakers.

And I was not referring to cellphones in the rest of the city, but the general EM background, especially since "up" is often considered a good way to vent EM without affecting users. (yes, I know, but still)

[jbjb]

Originally Posted by DawnFalcon

...Completely unshielded speakers.

And I was not referring to cellphones in the rest of the city, but the general EM background, especially since "up" is often considered a good way to vent EM without affecting users. (yes, I know, but still)

It's irrelevant that they are unshielded - the point is simply that the interference shows that, in that part of the spectrum at least, the interference caused by a nearby cellphone is greater than that caused by the EM background, and hence the blanket assertion you made is incorrect.

/JB

[DawnFalcon]

No, it's totally relevant. Because the entire point is that aircraft electronics /are/ shielded, and that shielding needs to be checked and fixed on a more regular basis.

And if you want to claim that city's EM background is negligible, you go right in believing that, I'll stick with the science. A cellphone affecting unshielded cables a meter or so away has no bearing on this.

[jbjb]

Originally Posted by DawnFalcon

No, it's totally relevant. Because the entire point is that aircraft electronics /are/ shielded, and that shielding needs to be checked and fixed on a more regular basis.

And if you want to claim that city's EM background is negligible, you go right in believing that, I'll stick with the science. A cellphone affecting unshielded cables a meter or so away has no bearing on this.

You really don't get it, do you? *You* made the claim - that the effect of the cellphone's emissions would be less than that of the EM background. I provided a counterexample which shows at least one situation in which it isn't. You're the one making the claim, so you're the one who needs to back it up.

Note that I'm *not* claiming that the city's EM background is negligible.

/JB

[DawnFalcon]

I do get it, I'm being trolled by someone with no conception of how EM radiation works. My bad for replying to him, everyone else.

[jbjb]

Originally Posted by DawnFalcon

I do get it, I'm being trolled by someone with no conception of how EM radiation works. My bad for replying to him, everyone else.

I give up. You're clearly not willing to discuss anything, nor back up any of your uneducated assertions with any evidence (or indeed any evidence of any understanding on your part of the science and technologies involved).

That's the last I'll say (to you) on this subject.

/JB

[DawnFalcon]

...

Yea, you go! You've made junk science claims, which show precisely how little you
understand. I'll just have to cut your claims up when you talk to anyone else, now, np.

[Lo Zeno]

I don't expect that you believe what I am going to say, since whatever source I provide you'll find another source that will tell the opposite of what I say, and I don't expect that you believe the fact that I have a degree in Telecomunications Engineering, but still I'll give you my 2 cents.

Any piece of microelectronics can become an antenna, but 1) it would works only on specific frequencies (depending on the material used, dimensions and thickness), usually not those used by a cellphone and 2) can be easily shielded with proper materials, so it's not a big deal, really. What I mean is that any sensible equipment that MAY cause problems by turning into an antenna for mobile phone's frequencies, is already shielded for good.
Antennas do not work for each and every frequency out there in the air: every antenna is built to receive a SPECIFIC set of frequencies. Is it a GPS antenna? It won't be disturbed by mobile phone frequencies. Is it a Digital TV antenna? it will receive DTV signals, not Radio FM ones. And so on.
Pilots and crews use radio signals to communicate with the ground during the lift-off and the landing, without any interference with the airplane's instruments at all. The only reason that brought nations to forbid the use of cellphones on airplanes was that back then, the knowledge of radio signals was not so deep and pilots feared that cellphones would "mess" with communications between the pilot and the ground. Specifically, the FCC commission in the USA (federal COMMUNICATION commission) wrote that "multiple radio sources might clog the communications with the ground".

Come to Europe, and you'll find dozens of flights that already allow you to use your mobile phone with no limits. And those planes didn't receive any "extensive shielding" or whatever... they simply had to undergo a series of tests which proved that using lots of mobile phones during their landing or lift-off didn't cause any problem (because government are made by people who do not have deep scientific knowledge, so they want "evidence" that it works).

As for EM background, x-ray, cosmic rays, and so on... we are blasted, everyday, by a HUGE amount of radio signals, you do not even have the idea. Yet, your television set works, your refrigerator does too, your car doesn't go "boom" and your train brakes safely when it reaches the station.

Also, if in my office we can let our largely unshielded PCs and servers work, while we keep our mobile phones nearby (and we even receive calls!) without noticing the slightest problem... you know, I think it's safe to say that mobile phone's radio signal do not interfer with electronics. We are 34 people, each one of us has a PC and a mobile phone.
Oh, and by "largely unshielded" I mean that the electronics are open, many of our oldest servers do not even have a case because they risk to overheat otherwise.

My 2 cent.
Everyone is free to disagree

[jbjb]

Originally Posted by DawnFalcon

...

Yea, you go! You've made junk science claims, which show precisely how little you
understand. I'll just have to cut your claims up when you talk to anyone else, now, np.

Sorry folks - can't resist.

Please name one junk claim I've made.

(Hint - I am professionally qualified in this area.)

/JB

[DawnFalcon]

Originally Posted by jbjb

That's the last I'll say (to you) on this subject.

Well, that establishes you're a liar...

(Hint - I am professionally qualified in this area.)

...Aaand I don't believe you.

So sorry.


Lo Zeno - Right.

[Toxaris]

Lo Zeno, you're absolutely correct. The equipment does *not* interfere with the electronics of the aircraft. They where afraid it might way back then, but a lot of tests have shown zero impact. Even in a lot of hospitals it is no longer prohibited to have a cell phone switched on (sound off though...), including the IC.

However, unfortunately regulations always are behind the real world. So, although I know it cannot do any harm, I do switch off my telephone. My e-book reader only when asked and that happens only 1 in 10 cases. I do not want to piss of a bunch of people keeping me in the air...

[jbjb]

Lo Zeno,

A very sensible post - I agree with almost all you say.

My only issue with any of this (which at least one other seems to have completely misunderstood, yet feels unable actually to *discuss* the issues) is that actually proving that some equipment is immune to a particular frequency is very hard. I'm not saying that there *is* a problem, simply that just because some unqualified passenger doesn't think there is is no reason to ignore a rule set by people who at least had some understanding of the issues.

I've provided many counterexamples to DawnFalcons unfounded claims, yet he feels unable to provide any answer to any of the questions I've asked him.

Incidentally my background in this comes from degrees in electronics and electronic engineering, and 30 years of working in the field.

(I know DawnFalcon won't believe this, but, frankly I'm past caring. I'm just replying to you because you seem willing to discuss it intelligently).

/JB

[Lo Zeno]

Originally Posted by jbjb

My only issue with any of this [snip] is that actually proving that some equipment is immune to a particular frequency is very hard. I'm not saying that there *is* a problem, simply that just because some unqualified passenger doesn't think there is is no reason to ignore a rule set by people who at least had some understanding of the issues.

I'll stick to my academic studies:
What they knew back then, was that radio signals were a largely unexplored fields. Now it isn't, and the increased knowledge has shown that many things we believed were partially exaggerated.
If I have to give you a scientific answer, I'll tell you that every single item in the world is actually affected by every single frequency of the spectrum. It's energy, after all :P you are blasted with energy, you are surely affected by it.
So, every piece of electronics inside an airplane is surely affected by mobile phones' signals. The point is that whatever the effect is, it can be ignored because it's too small.

At this very moment, my body is blasted and repeatedly hit by a million different radio signals, infrareds, x-rays from deep space, GPS signals, mobile phones all around me... yet I am fine so is my PC.

It's not that hard to determine how an item is affected by the energy provided by the radio signal: you can measure the change in temperature, magnetic changes, increase/decrease of electricity, increase/decrease of frequency... once you determine that its effects can be ignored (technically speaking, the interference becomes simple "noise" which can be easily filtered by a band-pass filter if necessary), you're safe. If they can't be ignored, wrap it in gum cables or add a thinner-band-pass filter. If they still can't be ignored, use a thicker cable.
(I'm over-simplifying, of course)
And that's just the kind of tests that airplanes are undergoing in UK right now, for example. Nothing more, nothing less.

[I've made a dozen or so edits to improve its readability... my English is getting rusty lately]
[And BTW, I'm not trying to tell that you should all go and use your mobile phones on airplanes. As Toxaris pointed out, it's not wise to piss off those who are keeping you in the air. I write this just so that if you happen to take an airplane and your neighbour doesn't turn off its phone, you don't die because of anxiety ]

[DawnFalcon]

Originally Posted by jbjb

Lo Zeno,

A very sensible post - I agree with almost all you say.

Then you were lying before, because it strongly contradicts your previous statements.

there is is no reason to ignore a rule set by people who at least had some understanding of the issues.

Right, which means people who have actually studied this, not you. And certainly not the American airlines, who have stuck their head in the sand over mobile phones.

I've provided many counterexamples to DawnFalcons unfounded claims, yet he feels unable to provide any answer to any of the questions I've asked him.

I did, you've just ignored them. And you are the one making grandiose claims about how your mobile is a magic interference machine.

I know DawnFalcon won't believe this

Nope, because you've admitted you're a liar. Go figure!

[pricecw]

Originally Posted by kovidgoyal

@pricew: Actually, you don't have to shield planes from all devices or even test each plane with every device. What you need is to establish a set of standards about the electromagnetic radiation permissible from electronic devices. In the US, the FCC already does this. The problem is that the FCC standards are incompatible with similar (though more rigorous) standards setup by the FAA.

Basically, what's really needed is for the FCC and FAA to co-operate.

And you really don't need to worry about random circuit boards becoming antennae. It's very simple to shield circuitry from EM radiation. Just put it behind metal. The problem is antennae, which cannot be put behind metal for the obvious reason that they need to receive EM radiation to work.

And if I understand the problem, as described in the reports with the GPS systems correctly, the problem isn't that a cell phone signal can cause a momentary loss in GPS tracking. This would be harmless, since software can easily compensate for it. The problem is that the cell phone signals have been shown to actually cause the GPS system to lose satellite lock, which then takes a significant amount of time to re-establish. I've never seen that happen with car/hand held GPS systems.

And finally, you don't need to upgrade the whole fleet all at once. You need to upgrade it a few planes at a time and remove the restrictions only on the upgraded planes.

@HarryT: Actually if you read the reports TimS linked to, even a single cell phone can cause problems. Undoubtedly more phones will make it more likely that a problem occurs.

The problem, the FCC regulates and has tests for Class A and Class B devices. What they are concerned with is if you are leaking a signal powerful enough to interrupt critical systems outside of your home or business. They are not concerned if you interfere with your TV, as long as you don't interfere with the neighbors TV.

I could probably dig up the testing (have been peripherally involved in the past) for consumer devices, but the whole thing is a very complex set of government docs I don't want to fully understand.

What is true though, I have seen the EM reports on products, one connector (say USB for arguments sake) from manufacturer A will leak EM horribly, a connector that looks to the naked eye as identical from manufacturer B will not leak.

Other issues, say you have SPI eeprom on your board, your main system chip supports 2 chip selects, so the vendor routes to 2 spots. Early production loaded both of the pads (ie the traces are terminated with a part), later the manufacturer went to one part. Now, the board has stubs on the circuit board that depending on length, routing, etc can be an antenna.

Now, the vendor has been say using a 10MHz clock on the SPI device, everything works well, but boot is slower than they like, so they do a firmware update that fixes a few things, and boosts the SPI clock to say 50Mhz, boot gets faster, but you have just introduced a faster clock to your potential antenna, no telling if that causes a problem. How do you test, generally, that is only accessed at boot, but if you change a permanent setting, it will access it.

It is easy to go on and on about theoretical problems, the issue is, none of us know unless we are actively working on it. Some places may have ruled that the risk of issues is low enough to allow use, others have not.

In the US it is currently a felony to refuse to follow the instructions of a flight crew, are you willing to risk arrest to read your kindle? Please lobby the industry/government if you don't like the rule, but don't risk others because you think you understand the art of EM interference.

--Carl