mobile phones

[Walsingham]

I was on the plane back to the UK yesterday and this woman next to me is chatting on her phone right through the announcements on safety and saying to her more conscientious friend on the other end that is wasn't really a problem and that it was some conspiracy with the phone companies.

 

Once she had finished this conversation at takeoff I leaned over and told her what I'm going to tell you. That is that the regulations are there for a bloody good reason. I happened to be travelling with a friend of mine who is a professor and world recognised expert in electronics and particularly wireless communications. He said precisely the same thing as me, with a good deal of technical explanation which I shan't repeat here.

 

I am raising this here in case you hear some bloke in a pub telling you it's OK. It's not. Turn your phone off, and if you see anyone trying to use theirs then stop them. They could be about to get you killed.

[thepixiesrock]

It really pisses me off when someone is on the phone when they tell you not to be on a plane, but can you give a little bit of technical explanation though? I've always wondered exactly why.

[kirottu]

I have understood that the risk isn

[Krookie]

They tested this on that show Mythbusters on Discovery Channel.

[Pope]

It's OK.

[mkreku]

There is no risk. It's a myth that somehow keeps surviving. The pilots use their phones all the time in the ****pit.

[metadigital]

Reminds me of an aeroplane engineer who was asked about flying; he stated that the only 'plane he would travel in was one with five engines. When asked why, he replied "Because they don't make a plane with six engines." :D

 

 

(Yes, they do.)

[Walsingham]

Listen, guys, and especially you mkreku. I don't care what you've heard about pilots, stewardesses or even God. This is nuts. I'm telling you the specialist word of a man who has spent his entire life in precisely this field ( my colleague). It's NOT OK. I happened to bring this up with a friend this evening and he informed me that we've lost chinook helicopters because of this issue. People were killed. Fact.

[tripleRRR]

Proof please!

[Walsingham]

I'll have to check what I should and shouldn't say about the technical side.

[Krookie]

Listen, guys, and especially you mkreku. I don't care what you've heard about pilots, stewardesses or even God. This is nuts. I'm telling you the specialist word of a man who has spent his entire life in precisely this field ( my colleague). It's NOT OK. I happened to bring this up with a friend this evening and he informed me that we've lost chinook helicopters because of this issue. People were killed. Fact.

 

Yeah, well my best friend is an expert in this same field, and HE says that it doesn't do anything to the plane. Actually, he told me that cell phones have been proven to SAVE lives on airplanes. People were saved. Fact.

[tarna]

I was on the plane back to the UK yesterday and this woman next to me is chatting on her phone right through the announcements on safety and saying to her more conscientious friend on the other end that is wasn't really a problem and that it was some conspiracy with the phone companies.

 

Once she had finished this conversation at takeoff I leaned over and told her what I'm going to tell you. That is that the regulations are there for a bloody good reason. I happened to be travelling with a friend of mine who is a professor and world recognised expert in electronics and particularly wireless communications. He said precisely the same thing as me, with a good deal of technical explanation which I shan't repeat here.

 

I am raising this here in case you hear some bloke in a pub telling you it's OK. It's not. Turn your phone off, and if you see anyone trying to use theirs then stop them. They could be about to get you killed.

Before I say that your friend is full of feces, I'd like to hear his ideas on this. I've worked with solid state and digital electronics and disagree with the 'premise' as stated. Digital signals are 'far!!!' different from the old analog technology and don't present the same threats to signal technology that the old crap did. My 'feel' to this is along the same line as the urban myth of cell phone causing fires at the gas pumps and causing brain cancer.

 

Show me the proof ( or a least give me a good hypothosis ). I'm open to a good arguement.

I'd like to hear the tech explaination that he offered to you. I do work with Denver International Airport as well as Centennial ( a little pissant airport ) and can probably get tower control to talk to me about this.

 

The old analog type of wireless communication relied on frequency and signal strength ( brute strength ) to get the job done as opposed to 'finese' that the digital communications do now. That was the whole point of digital signals. What became limited by frequency bandwidth became an open market due to the availability of sub-bit encoding that digital signals offered. Hell... even air conditioners ( commercial ) using addressable communicaions these days. It used to be that someone 'keying' a radio or cell phone around me would drastically affect my metering instruments. Now, I don't even notice it in my work. Check out the trunk signals that law enforcement uses to prevent police scanners from picking up their communications. Denver uses this and you have to have a special scanner to listen in on their communications. I'm fairly sure that the budget available to United Airlines is a bit more than that of the Denver Police Dept. ( Denver has used a digital truncated system for about 15 years now. I know this because I used to listen in on them ). Besides the obvious benefits in having less morons listening in on their chatter, it also adds the the availability to bandwidth options. Multiple users on the same frequency but using different 'addresses' . Most every communication system these days use similar technology and have for many years. An airplane that has not has such an upgrade should raise a red flag to anyone considering flying on said craft as it says something about the airlines using old-ass technology when an upgrade would be fairly inexpensive.

 

I happened to be travelling with a friend of mine who is a professor and world recognised expert in electronics and particularly wireless communications.

I'd like to avoid these sort of mentions since George W Bush is also 'world recognised' as a representantive of the US and we all know what a slug of crap he is. Let's stick with the arguement/theory and the discussion can stay a little less 'personal' and a bit more open to attack and less to personal insult that way.

 

I realise that I'm just a dumb mechanic but I don't take 'anyone's' talk as anything more that bullsh*t unless that 'talk' can be backed up with a good arguement. I don't require 'proof' to back up the position, just a good working hypothosis. Besides...argueing theory can be fun as the possibilities can be endless! :wink:

[theslug]

slug

Don't use the slugs name in vain plz.

[tarna]

slug

Don't use the slugs name in vain plz.

Oops! Would puss filled pocket of pestulence be a better term to describe our esteemed presidente ( 'Baby Doc' Bush )?

[Walsingham]

I _am_ sorry, but I will have to check which bits of what he said are fair game, and what is the result of any confidential work. This could take a week or so.

 

Out of interest, if you chaps decide it is significant then will you do anything about phone use?

[metadigital]

I don't usually use my mobile phone on an aircraft. Kinda hard to get coverage at 30000 feet.

[Walsingham]

I do know that that is part of the problem. Some phones ramp up their power output in order to try to get a signal.

[Guard Dog]

Now here is a topic I can answer somewhat intelligently on. I am an RF Engineer for a major US based cellular company (hint: the biggest one) so this is a little up my alley. First of all, most US based cellular networks operate in the 800 MHz range. These phones/networks pose no danger to aviation systems, air traffic control systems or navigational systems.

 

However, some networks in the US and many in Europe and other places operate in the 1900 MHz range. These devices may interfere with the TCAS (anti collision) systems in some types of air craft. Most TCAS systems operate around 1095 MHz but there are some that operate at 2085 MHz and there is a slight possibility of momentary interference from a 1900 phone. That said I have never heard of a single instance where that has happened.

 

I agree with Meta, it always surprises me you can even get coverage in an airborne airplane. First of all, the cell sites generally do not have a high power output. In an urban area ERP is usually between 1 to 10 Watts max (30-40 dBm). Because there are usually a lot of cell sites you don't want any one handling traffic in the coverage area of another one. To further shrink the footprint of the cell we downtilt the antennas a few degrees so they are angled slightly towards the ground. This means that a handset in an airplane is receiving off the back lobe (reflection from the antenna rear) which in most antennas is less than 30% of the main lobe power. So if a cell has an ERP of 10 watts the back lobe will be at best 3 watts. Its no small feat for a 3 watt transmission to travel through 4 miles of air (which has clouds, several thermocline's, and other interference) to the airborne handset. Further, most handsets have a max power of 0.3 watts so it is even LESS likely the handset can get back to the cell.

 

Because of the physics of radio wave propagation (I'll give a more detailed explanation if needed) an 850 MHz signal will travel farther than an 1900 MHz signal with the same ERP. So if your phone even works in a plane, it's probably an 800 MHz anyway so there is no need to worry.

Edited June 11, 2007 by Guard Dog

[thepixiesrock]

I still believe in you Wals. I still believe in you.

[theslug]

I still think cell phones should be restricted during flights becuase I hate obnoxious people who talk on their cell phones.

[metadigital]

Carried unanimously.

[taks]

guard dog is pretty much dead on with his analysis. really it depends upon which systems are in place on the plane. also, the biggest problem is NOT the ground cells, since their signals are present regardless of whether you have your phone on or not. the phones are actually the bigger problem as they're putting out a few hundred milliwatts, and they're doing it from less than 100 feet from the systems that are at risk. since a phone at altitude is going to be nominally well beyond the typical cell range, it will have to boost its power to the maximum level to operate.

 

taks

[Guard Dog]

guard dog is pretty much dead on with his analysis. really it depends upon which systems are in place on the plane. also, the biggest problem is NOT the ground cells, since their signals are present regardless of whether you have your phone on or not. the phones are actually the bigger problem as they're putting out a few hundred milliwatts, and they're doing it from less than 100 feet from the systems that are at risk. since a phone at altitude is going to be nominally well beyond the typical cell range, it will have to boost its power to the maximum level to operate.

 

taks

 

One other note. A GSM, TDMA, or AMPS phone sends a signal to it's controlling cell every 3 seconds while it is powered on. So you do not need to use the phone for it to be a potential interference. CDMA does not. But again, it is pretty unlikely it will be a problem.

[Walsingham]

I still believe in you Wals. I still believe in you.

 

Thanks, buddy!

 

I can confirm that interference between transmission frequencies is part of the problem. Particularly the anti-collison radar as GD says. However it is not the only issue.

 

I think that, to be perfectly honest, it also annoys me that someone would ignore the safety advice at all. It's not supposed to be open to personal tastes!

[LadyCrimson]

I still think cell phones should be restricted during flights becuase I hate obnoxious people who talk on their cell phones.

So agree.

Not only on planes, either.