Receivers of ANY kind generally emit RF.
I think you mean 'tunable' when you say 'generally'.
There are passive designs that don't have an oscillator so they don't create potentially harmful interference. (i.e. a crystal detector that amplifies the demodulated audio.)
http://www.edn.com/article/CA529386.htmlhttp://www.techlib.com/electronics/aircraft.htmhttp://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=ABM1Of course they're not tunable and only usable to receive strong transmissions very near to you.
BTW, has anyone tried the Ramsey unit?
Wi-fi (IEEE 802.11) currently uses the 2.4-2.5 GHz band. Radios and navigation equipment use 108-137 MHz, neither of which will conflict with each other.
I don't necessarily disagree with you, but here are a couple of points for some more depth on the topic...
1. Modern scanners/etc have super-heterodyne tuners, which by definition generate RF on multiple frequencies as part of the mixing process prior to demodulation. It's very possible that a super-heterodyne receiver will generate RF on the additional frequencies on which aeronavigation systems utilize. (see #2).
The worst case here is a receiver that is leaking 'too much' RF and causing reception issues on the navigation/communications equipment.
This problem probably doesn't surface with well-designed, properly functioning, type-accepted receivers; but what about malfunctioning or questionable consumer-grade equipment brought on board by a passenger? It's just easier for the governing body to issue a blanket restriction to prevent any possible scenario where a radio receiver could interfere with critical navigation/communications.
http://abcnews.go.com/Technology/AheadoftheCurve/story?id=6833039&page=1I haven't been on any of the new aircraft with the 802.11 capability, but I'm willing to bet that they turn off the 802.11 access points prior to final approach/landing. Any one know if this is true?
2. 108-137Mhz is only one part of the radio spectrum that the modern aircraft uses for navigation and communication. (Also regarding 802.11 in the US; 'a' and 'n' can also operate 5Ghz, and recently 'a' will be allowed to use 3.7Ghz as well)
Here's a few other parts of the radio spectrum I've identified that modern aviation uses for navigation/communication. I'm still building a list but here's what I have so far...
329.15-335.0Mhz - GlideSlope/GlidePath
960Mhz-1215Mhz - Distance Measuring Equipment (DME)/TACAN
1176.45MHz, 1379.913Mhz, 1381.06Mhz, 1227.60Mhz, 1575.42Mhz - GPS
1030-1090Mhz - ADS-B 1090ES
978Mhz - ADS-B UAT
75Mhz - ILS Outer Beacon
145-530Khz - Non Directional Beacons (NDB), DGPS