[FoRK] Disruptions: Fliers Must Turn Off Devices, but It's Not Clear Why

Stephen Williams sdw at lig.net
Tue Dec 6 01:13:23 PST 2011


Aircraft avionics are far different.  And they are far away behind 
metal bulkheads.  Your speakers are totally unshielded with the 
cheapest amp that would work.  Good speaker systems (I've had a super 
multi-input (including optical) Logitech for a few years) are totally 
immune to this.  Cheap speakers are essentially near-field receivers 
that will amplify a certain range of frequencies.

If you can actually hear the words you are speaking over the speaker, 
then either you are not hearing it from the traffic between the phone 
and the tower, or you are using analog cellular which has been unlikely 
for over 10 years.  GSM phones have a characteristic repeating pattern 
that is called "galloping horses".  This is probably what you are 
hearing.

Aircraft avionics have to operate perfectly when there are AM aircraft 
radios blasting transmissions at several watts, plus many other 
electronic devices, plus engine ignition noise.  Plus they have to 
survive lightning hits to the aircraft, and very dry and therefore 
high-static situations.

A cell phone maxes out at 800mw.  Bluetooth is a few mw: class 1 is 
100mW, 2 is 2.5 mW, and 3 is 1mW.  I've never found a class 1 device 
outside of embedded industrial units.  Wifi is limited to 1W but things 
like laptops are 36mW max.[1]  Something like a Kindle, without radio 
on, is micro watts or something similar.  Static in people's sweaters 
is probably a worse radio threat.

Any study of this shows there are no problem.  Further, as soon as the 
airline finds a way to make money on it, suddenly it isn't a safety 
problem anymore.  Nearly every cross-country flight, I now use Wifi 
service which technically could transmit at power greater than modern 
cell phones.  And cell phones have been allowed on some flights.  They 
are only going to be disallowed because of social irritation.

There are only two types of radio that I'd be worried about: GPS 
jamming and using an aviation radio to interfere with voice or VORTAC 
transmissions.  I'm sure with most aircraft, even if you had those 
you'd have to rig them to transmit impossibly strongly to interfere 
with an optimized skin antenna from inside a metal tube.

[1] http://wiki.robotz.com/index.php/FCC_Regulations_on_WiFi

sdw

On Mon Dec  5 23:33:12 2011, Damien Morton wrote:
> My cellphone sits on my desk. Right near my other USB connections.
> keyboard, mouse, disk drive, etc. When my phone rings, I can hear the
> conversation between phone and tower on my speakers, and invariably,
> that conversation disables my usb connection such that I need to reboot it.
>
> Maybe aircraft are different and special when in comes to induced RF
> interference. I dont know really, but my basic position on this is "fuck
> all y'all ipads and shit"
>
> On Tue, Dec 6, 2011 at 2:38 AM, Stephen Williams<sdw at lig.net>  wrote:
>
>> Fake security&  false risk aversion, not to mention outright institutional
>> lying, bugs me.
>>
>> Disruptions: Fliers Must Turn Off Devices, but It's Not Clear Why.<
>> http://www.wirelessdesignmag.**com/showpr.aspx?PUBCODE=055&**
>> ACCT=0000100&ISSUE=1111&**RELTYPE=IN&PRODLETT=OM.html?**
>> et_cid=2354456&PRODCODE=000000<http://www.wirelessdesignmag.com/showpr.aspx?PUBCODE=055&ACCT=0000100&ISSUE=1111&RELTYPE=IN&PRODLETT=OM.html?et_cid=2354456&PRODCODE=000000>
>> **>
>> http://www.wirelessdesignmag.**com/showpr.aspx?PUBCODE=055&**
>> ACCT=0000100&ISSUE=1111&**RELTYPE=IN&PRODLETT=OM.html?**
>> et_cid=2354456&PRODCODE=000000<http://www.wirelessdesignmag.com/showpr.aspx?PUBCODE=055&ACCT=0000100&ISSUE=1111&RELTYPE=IN&PRODLETT=OM.html?et_cid=2354456&PRODCODE=000000>
>>
>> sdw
>>
>> 


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