At 06:38 AM 6/27/04 +0200, Thomas Shaddack wrote:

If the phone is shielded, it can't transmit/receive, which makes it rather useless. :(

When you don't want to use it, why should it not be useless?

There is one potential landmine as well; the inherent ability of any device containing resonators to behave like a crude RFID tag. I heard somewhere, and my memory may be failing, that it is possible to irradiate the phone with the frequency of the cellular band, and it faintly resonates and returns back its own echo, which has minute variations given by type, manufacturing tolerances, and possibly age of the phone, giving it a kind of unique signature. (This could potentially apply also to radios and transceivers. Does anybody have any idea if it is possible to do such kind of "active fingerprinting" of rf devices? This way it should be possible to detect even powered-off devices like hidden transceivers or body wires; take a transmitter, sweep the spectrum, and watch echoes on

the receiver - there could be peaks on the frequencies of the tuned circuits inside the examined device.)

Your "second order effect" physics is on target. Nonlinear devices generate harmonics when tickled. All devices vary and have characteristic RF signatures. I read something about that recently somewhere, but memory fails.

Question to RF heads here: could it work?

I'm not an Elmer but I pretend to be one on the internet.