Paul Saccani wrote:
> On Tue, 16 Sep 2008 08:38:45 +1000, B J Foster
yahoo.com>
> wrote:
> >> Mobile phones use UHF frequencies and do *not* interfere with aircraft
>> navigation systems. The issue is that whilst the interference is
>> infinitesmally small it cannot be entirely dismissed - so the rule
>> remains. In practice it is ridiculous.
>
> I've actually seen mobile phones interfere with VOR, the needle
> swinging from side to side until they are turned off.
I find this very hard to believe.
The VOR band is 108MHz to 118Mhz (VHF). The lowest mobile band (UHF) is
900Mhz. If the VOR system has such a poor filter then it is going to be
affected by *every* *other* system between VOR and GSM.
For example:
118ق137 MHz: air traffic control
137-138 MHz: meteorological satellites
144ق148 MHz: Amateur radio
156ق158 MHz: VHF Marine Radio
175-216 MHz: television channels 7 - 13
174ق216 MHz: wireless microphones
...and so on...
NASA and U Okalahoma tested GSM and CDMA extensively and concluded as
follows:
"None of the 4 CDMA and 4 GSM wireless handsets tested would
individually be likely to interfere with aircraft VOR, LOC, GLS,
or GPS navigation radios".
(the safety margin for GSM was calculated as 47dB)
http://www.humanitarianinfo.org/sumatra/mediacentre/press/doc/article/Electromag...
They also found that "Interestingly, repeatedly turning the handset
power on-and-off caused the most significant changes in the spurious
radiated spectrum".
This seems to dovetail with my earlier speculation:
"I have a feeling that the CPUs within the devices actually cause more
interference"
> Thus, "do *not*
> interfere with aircraft navigation systems" would seem to be somewhat
> of an overstatement. Interference with VOR has been reported quite a
> few times.
Do you have a reference?
> Aircraft should be designed to cope with such issues -
> but it might surprise you to learn that quite a lot of aircraft were
> made before mobile phones were invented. Australia doesn't have a
> blanket ban on mobile phones being used in the air, but it is
> certainly within the rights of operators and air crew to prohibit
> their use at any phase of flight. In practice, this isn't ridiculous
> - aircraft systems can develop faults, just like any other systems and
> be more vulnerable than they should be to interference.
>
> The US FCC does prohibit the airborne use of a number of types of
> mobile phone in the air for spectrum management reasons, rather than
> air safety..
GPS?
