Re: GPS tracking device allowed in commercial flights?

From: Alan Browne (alan.browne_at_FreeLunchVideotron.ca)
Date: 08/17/04 

Date: Tue, 17 Aug 2004 10:20:52 -0400

Meindert Sprang wrote:

> "John Miller" <me@privacy.net> wrote in message
> news:cfsun4$slf$2@n4vu.com...
>
>>kashe@sonic.net wrote:
>>If you've ever heard the sounds produced by a cell phone in an AM radio
>
> (the
>
>>aircraft comm radios are AM), then you're able to make a pretty good guess
>>as to the cause of the interference.
>
>
> There is a world of difference between a cheap broadcast AM radio and an AM
> VHF radio used in an aircraft.
> The interference caused by a cell phone exists because unscreened parts of
> the circuit of a cheap radio pick up the 200 HZ frame rate of the cell phone
> carrier and rectify it to a 200 Hz audible LF signal. The cellphone
> interference is NOT entering the radio by it's antenna.
> An aircraft radio is completely screened and the only place where RF signals
> can enter that radio is through it's antenna connection, which has a band
> pass filter that blocks anything except air band frequencies.

The risk to interference in avionics is at many places, including
antennas. Given the large variety of aircraft configurations,
wiring runs and many unknowns, it has been deemed unsafe to
operate any kind of transmitter aboard an aircraft. Commercial
aircraft antennas range from fairly low frequency (ADF receivers)
to very high (weather radar in x-band). Some antennas have
filters at the mounting area, some do not but rely on in-chassis
filtering.

When laptop computers came out, interference with navigation
equipment was noted with several cases of aircraft on autopilot
entering long period oscilations.

>
>>If you doubt that it can be heard, carry your TDMA or GMS phone into your
>
> or
>
>>a friend's airplane, turn on the comms, and make a phone call.
>
>
> And you'll be fine. As a test, I just ran my cell phone 4 inches away from
> the antenna of my VHF set, switched to AM and SSB. No interference could be
> detected, as expected.

Your test is hardly exhaustive or conclusive. See RTCA DO-160D
for guidance.

When my cell phone (on, but not in use) is under my car radio
there are occasional bursts of modulation lasting 5 seconds or so
when the cell and phone conduct some back channel communication.

Interference does not occur uniquely via an antenna. Poor
chassis shielding, poor wiring harness/connector shielding and
filtering are among the many ways that signals get into receivers
and can interfere.

The rigorous exigencies of DO-160D (sections 18 thru 20) in this
regard speak for themselves.

Cheers,
Alan 

-- 
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--

Relevant Pages

  • Re: GPS tracking device allowed in commercial flights?
    ... what does this tell you about possible interference of a cell phone? ... A cell phone is only supposed to emit signals within its band. ... Well, I think a VHF radio, beit a ham radio or an aircraft radio, are of ...
    (sci.geo.satellite-nav)
  • Re: GPS tracking device allowed in commercial flights?
    ... >>The risk to interference in avionics is at many places, ... >>operate any kind of transmitter aboard an aircraft. ... >>aircraft antennas range from fairly low frequency ... is under my car radio ...
    (sci.geo.satellite-nav)
  • Re: GPS tracking device allowed in commercial flights?
    ... >>guess was that the cell phone signal was getting into the intercom. ... > No, the intercom doesn't pick up radio signals, it's a closed circuit. ... You used it in your aircraft and you did not detect interference ...
    (sci.geo.satellite-nav)
  • Re: mobile phones
    ... not be operated while such aircraft are airborne. ... May "Cell phone use in gliders" rest in peace. ... Modern networks don't have this problem so this reason goes away. ... GA pilots the interference thing isn't too important, ...
    (rec.aviation.soaring)
  • Re: GPS tracking device allowed in commercial flights?
    ... of interference from a cell phone in any aircraft radio. ... often to get ATC clearances at remote ...
    (sci.geo.satellite-nav)