Alexey Feldgendler wrote: > Except GPS, I guess. Because GPS is just a receiver, it cannot add any > interference and hence doesn't need to be disabled. Actually, GPS could > provide some fun in a flight.
NO. Including GPS. Every flight I've been on recently has state that electronic devices which send *or* receive signals are not allowed (or those capabilities switched off.) Part of the process of receiving signals involves heterodyning--basically mixing a received signal with lower intermediate frequencies (IFs) to amplify the desired actual signal, while making the carrier signal something easier to work with. See http://en.wikipedia.org/wiki/Heterodyne for a very basic description. Any oscillator will radiate some electromagnetic interference. Furthermore, because the intermediate frequencies are often similar (or in the case of GPS identical) to other such devices, those stages can interfere with each other. For another example, in states where radar detectors are illegal, the police can use sensors tuned to the first stage IF (around 900MHz IIRC) of the radar receiver to find cars that have them onboard. (http://radar.757.org/VG2.htm) As the onboard electronics in aircraft are upgraded to those designed in an age of digital electronics, Bluetooth, GPS, cell phones, etc, these restrictions will probably fall by the wayside. However, today the regulatory agencies have to look at the least capable machinery flying out there when they make the rules. Most airlines also tend to over-generalize things simply because it makes it easier to communicate what is allowed and what isn't. - John
