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Mayor / Maire

Re: Cell phone won’t connect to network - NS

@LurganIeUk 

 

Airplane mode turns off the radio hardware. (Or at least it's supposed to.)

 

When Airplane mode is ON the phone won't transmit any signals so it can't connect to cellular, WiFi, or Bluetooth (because they all use two-way signal handshake protocols). It might or might not still be able to receive radio (FM broadcast, passive GPS, etc) but that depends on how the hardware and software were implemented.

 

When Airplane mode is turned OFF the phone will immediately attempt to (re)establish wireless connections across radio. It can even authenticate a connection stronger (more signal bars because it's reasserted itself with the network) than it had before.

 

Airplane mode ON is also useful when charging the phone. Batteries can charge *much* faster (and stay cooler) when not simultaneously discharging power (across radio).

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Mayor / Maire

Re: Cell phone won’t connect to network - NS

 @Korth 

I have a few models of phones and I can individually turn on radios on them while airplane mode is on. I would have to imagine that's true for many phones. Airplane mode does shut everything off...but ...

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Mayor / Maire

Re: Cell phone won’t connect to network - NS

The whole reason it's called "Airplane mode" is because it was initially conceived to let people bring their phones (and laptops and stuff) onto airplanes.

 

Passive radio reception is fine. Listening to radio is fine. You can even buy passively-tuned non-oscillating radio sets which eavesdrop on air traffic communications, though these days they probably won't let anyone bring such things onboard commercial flights.

 

But active radio transmission causes problems with the instrumentation onboard commercial aircraft. Lonely phones desperately searching for a friendly network will ping constantly at maximum allowable power (150mW) when they're out of range - a few kilometres above - the nearest cell towers. A lot of radio noise when every passenger carries a phone. Especially since they're all confined within a big electrically-grounded metal tube which leads right towards the cockpit avionics.

 

I've seen phones go both ways on this. Some will still allow radio reception. Some will completely shut down whatever circuit blocks control the radio hardware. Some (many) are just equipped with bad software which ends up (intentionally or unintentionally) limiting what users can do. (I often Airplane mode at remote job sites to save battery. And I've used a good variety of devices, though I admittedly don't buy into flagship $$$$ phones which probably offer better engineering.)

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Mayor / Maire

Re: Cell phone won’t connect to network - NS

With all due respect to airport personnel, there is no risk in having cell phones transmit on a plane.

 

Cell phones use different frequencies and if there was a real risk, serious efforts would be made to prevent people from bringing them onto planes.

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Mayor / Maire

Re: Cell phone won’t connect to network - NS


@sheytoon wrote:

With all due respect to airport personnel, there is no risk in having cell phones transmit on a plane.

 

Cell phones use different frequencies and if there was a real risk, serious efforts would be made to prevent people from bringing them onto planes.


I've heard arguments both ways. An aircraft pilot explained to me how phones and laptops don't cause any problems at all. A ham radio nerd explained to me how phones and laptops cause all sorts of radio havoc.

 

It's even been argued that active phones moving too rapidly across or between the ranges of cellular base stations also cause some problems with ground-based networks. Though I honestly don't know how plausible this is, cellular network engineers could probably clarify the (in)validity of this claim.

 

But the fact is that, regardless of the technical specifics, airplane mode is (or was) a legal requirement for some airlines. Even if it's not strictly necessary, even if it's not consistently enforced, it's still a feature built into every phone. A feature useful in other ways.

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