Ah, somebody throwing his teddy out of his cot.....
Back to serious matters.
I'm amazed nobody picked up on
matt_hooks post.
Well, I can definitely say, without a shadow of a doubt, that a mobile phone left switched on CAN have an effect on navigational equipment, namely the NDB. This is in a light piston twin, but it proves that they can cause emissions in a wave band that might interfere with navigational equipment.
He obviously did not make this up, and the link between "cause and effect" looks reasonably well established.
At first sight, there's something very wrong with this picture... an NDB transmits somewhere in the 190 - 1750
kiloHertz band, a cellphone somewhere around 800 or 1800
MegaHertz.
But.... most digital devices emit radiation on other frequencies as well, such as harmonics of the processor clock.
And if the cellphone ringer is driven with a nice squarewave, harmonics of that can very well get into the NDB band as well.
I feel this "spurious" radiation, totally unrelated to the nominal frequency the device works on, be it a cellphone or WiFi, is being neglected too much.
I remember very well doing EMC testing on a DAFS computer prototype (both conducted and radiated EMI)... we were disagreeably surprised by some of the unexpected frequencies and levels where we had problems.
The difference was of course, that we had to fix it to get certified.
Unlike your cellphone.