Mobile phones and electronics

I have always been confused by this, if a mobile with a very weak signal is considered capable of affecting instruments and controls then why are mobile masts putting out far more power allowed at Heathrow, Gatwick et al?
 
Same with hospitals. Signs say "Switch off all mobile phones" supposedly as they can affect vital electronic equipment but I know that the majority of staff carry and use their mobiles on the wards. Another urban myth?
 
I discovered that I was not allowed to use my mobile whilst putting petrol into my car, when the garage attendant would not turn on the pump and drew my attention to the sign instructing that as well as engines being turned off, mobiles were not to be used whilst filling up.
 
Probably more likely to cause problems than sunspots. /forums/images/graemlins/smile.gif

Best reason for not keeping a mobile near your helm, though, is the deviation it will induce in the compass.

Rick
 
There has been at least two petrol forecourt fires attributed to mobile phone use whilest filling with petrol. The theory is that a static spark can occure and ignite the vapour that is emitting from the filler tube. The question of interference with electrical equipment, I am not yet convinced of this.

Ex petrol pump attendant.
 
I did have a problem on our last boat when I had an incoming mobilephone call whilst I was standing at the wheel, the phone was within 3ft of the autopilot control box but a long way, maybe 15ft or more from it's compass. The boat suddenly turned 90 degs right but fortunately we were way offshore with no other boats around and only doing about 6kts. The first time I put it down to a pilot glitz but it did exactly the same when another call came in 30 minutes later!

It would be a big problem on a big mobo at speed!
 
Mythbusters experimented with mobile phones and fuel spills. As I recall they could not induce any sort of ignition, even after doctoring the phone for maximum output, etc. From a technical point of view, I cannot see transmission from a mobile phone being able to induce enough voltage into any metalwork to creat a spark - but what do I know, I'm only an electronic engineer?

Don't forget, "inverse square law" applies to the phone transmission, to the effect that more than a foot or two away the power density is too small to even measure! By the same token, I can't see it affecting even the most sensitive equipment, providing it has adequate filtering. I would think twice before using a phone near a heart monitor (or similar), but still doubt you would see any effects.

As for your compass, there should not be any polar magnetic field from a phone, or other transmitter.
 
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I have always been confused by this, if a mobile with a very weak signal is considered capable of affecting instruments and controls then why are mobile masts putting out far more power allowed at Heathrow, Gatwick et al?

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Suspect its down to the inverse square law, more power is getting to the planes electronics (if you are sitting in first class or near a remote electronic doodah) from your phone that from that mast 3/4 mile away.
Apart from which, you are INSIDE the (obviously not very good - or you wouldn't get a signal) Faraday cage, the mast is outside.

Edit Mikef2 got there before me!
 
Mobiles do interfere with electronics. Have you never heard the noise from your car radio when your phone is about to ring or the interference on a TV when you use a mobile next to it.? Also causes problems in my line of work. Never seen sparks from a mobile phone but have seen them from dodgy wiring and ignition systems on cars, far more likely that a fire would start from that.
 
I think the story is apocryphal.

I doubt you could raise a spark on the potential you could generate between a mobile and your hair.
Any spark is more likely to come from dissimilar materials i.e. between upholstery and clothing.
How many times have you got a whack of lecky from your car door while getting out?
And even then, you need a spark with sufficient ENERGY to ignite the gas, plus a mix of gas and air within fairly tight upper and lower levels - and the spark to happen in the right area.
This all adds up to a pretty unlikely combination.

The only way I can see to obviate the (percieved) problem is to only fill your car up while naked and with your hair shaved off (yes, all of it!).
 
Well, I'm supposed to be working so I didn't do much research (ie I took the first Google hit that came up) and my source is a bit "populist" (though it makes reference to some more authoritative sources so...
How about this?
 
The issue with mobile phones (and other items of electrical equipment) is not so much the RF power output but the risk of sparks from the battery if the device is dropped, plenty of current available for a juicy spark. You will not be allowed into any oil processing site with a mobile phone, even switched off.

I have come across a reported instance of the fuel filler pipe on a vehicle acting as a waveguide and arcing across in an RF field, but there was several Kw of peak power involved in that case :>)
 
maybe the hair thing would have happened with any bit of charged plastic . I seem to remember charging combs as a kid. was she wearing silk undies and a woolen jacket, I wonder.
 
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This all adds up to a pretty unlikely combination.


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OK but filling up a car with petrol is a very very frequent event. One in ten million chance multiplied by one million fill ups a day ............................. or whatever the numbers are
 
I agree with this.
But as a risk assesment - the consequences of a spark in a petrochem plant are more significant than in a forecourt.

What are the chances of:
1 dropping phone combined with:
2 creating spark combined with:
3 finding a pocket of volatiles on well ventilated ground (liquids not likely to catch from a spark)

compared to the chances of static spark at the filler cap with volatiles - that you can even see - spilling out?

At what level of risk do we draw the line? (as far as I know no-one has ever collated stats for "dropped non-intrinsically safe electrical items on a forecourt")

Maybe we should ban remote locking keyfobs too?
 
So how many real garage forecourt fires have you heard of?
The papers are just full of them! /forums/images/graemlins/wink.gif
 
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