If I leave my cell phone near my computer speakers I will hear occasional buzzing, clicking, etc. Before the phone begins to ring, I hear a dah..dah.daahhhhh. I know this is RF interference being picked up by the amplifier in the speaker. If one were to record this sound with a microphone at 11 or 22Khz, would it be possible to obtain any information (usable signal) from the recorded audio? Thanks, snipped-for-privacy@muderick.com
If you could then clean up the audio into a reasonable digital waveform, in the right format, and somehow then get it into a cellphone provider's software package, then I guess that you could, but I'm not sure that it would tell you anything useful. AFAIK, it's just a response from the phone, to the question " OI !! Are you still there ? Yes ? OK, let's set up a channel 'cause I'm about to ring you " or something along those lines, sent by the last cell that the phone had become registered on. Perhaps others on here know a lot more about it, but I think that's something like I remember reading it.
Of course, what you're hearing may not be a data stream as such, at all. It may just be as a result of the phone's RF output frequency hopping about all over the place on some kind of spread spectrum scheme. Again, others here might be able to give a better answer on that.
Arfa
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