| Re: Mobile phone interference |
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Group: aus.aviation · Group Profile
Author: David LesherDavid Lesher Date: Sep 17, 2008 10:21
B J Foster yahoo.com> writes:
>> 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.
You don't seem to understand RF very well. Lots of weird things happen,
when you mix multiple emitters and Murphy.
First of all, GSM phones emit subcarriers, specifically the harmonics
of its switching speed. They tends to get into LOTS of things such as
hospital telemetry.
Second, the front end of a the VOR is 100 Mhz; but the IF's are often
poorly shielded; put an emitter near by them and....
Years back, a friend was in a FAA test aircraft, ISTM it was the old
727 they had, and while testing a new Mode-S transponder, all was
well...until they came in to land, the gear cycled and the GPWS went off
when the radar altimeter went bonkers. It had been tested BUT oops when
the gear doors were open in transit, it reflected enough RF back that...
There's another gotchas out there in aviation, like O2 bottles.
Let's not add move variables.
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