I find some of the empirical testing made here a little worrying....
Some facts:
Avionics equipment is certified for radiated RF field immunity. Notice that this is 'RF field' and is in Volts/metre.
A cellphone has an RF output power of max 2Watts. The RF field generated depends on the distance from the antenna. A few feet from the antenna and the field will be around 10V/m. A few tens of feet and it will be below 1V/m.
However the cellphone is a portable device and could be placed a few inches from aircraft wiring etc and the field at that distance is MUCH higher and 'may' exceed the certified immunity level.
Also most equipment is tested for immunity in relatively small test chambers. It is not commercially viable to made radiated RF immunity testing of fully wired and integrated systems let alone complete commercial aircraft. But the overwhelming probabilty is that the total installation complies because the individual parts do. But there is no absolute guarantee.
Radiated RF susceptibility is a phenomena that requires a specific level of RF field on a discrete frequency (ie a resonance effect).
Wi-Fi is an example of spread spectrum technology. The RF power may be 100mW but that is the total RF power that is spread across many MHz. As an analogy you can think of Wi-Fi as being 100's of RF carriers of less than 1mW each. So the RF field at any discrete frequency will not represent any RF susceptibility threat.
No doubt when DO-160 version F arrives we will find that required testing and levels for RF immunity have been increased yet again.
ps: As for the comments about 25 year old TSO transceivers being immune. Quite possible, most of those I tested in the past were so insensitive that it was not suprising that they heard so little interference
