[RFI] cellphones on airplanes

Jim P jvpoll at dallas.net
Thu Mar 2 21:40:02 EST 2006

> My first inclination is to say, "horse-hockey".
> But the reality is that the GPS bands and cdma/tdma phone bands
> aren't all that far apart...there could be a question of
> fundamental overload, if enough cellphones were transmitting at
> high power.

Can you say "transmitter intermodulation"?

  Background: Multiple phones in close proximity can ceate 
  some not so insignificant levels of 3rd and 5th order Imod
  products; now imagine every fifth person on board that 
  aircraft with anactive call at max PL (power level).  

Can you say "creating new mixing product in the presence of 
other digital devices"?

   Background: I witnessed this phenomonon while on two fronts a 
   few years back at a lower frequency:

  a)  Electronic ballast fluorescent lamp 'mixing' with a six meter
   repeater carrier and generating an on-receive channel signal.

  b) While doing development of a wire-wrap embedded micro-
   processor based box I again experienced the same phenom 
   with that same six meter box. (Part of the cure involved an 
   RF choke 'plane' below the 6M antenna)

Now imagine the RF environ in a 'reflective' tube with a few life 
forms occupying the lower three feet (when seated) with lap
tops and iPods and handheld video games all active at the
same time ...

There's your beginning scenario.

Jim P  //  WB5WPA  //

More information about the RFI mailing list