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Snooping Through Walls with Microwaves
denis-The-menace writes "According to an article from newscientist, scientists have devised a system to use microwave energy for surveillance. If people are speaking inside the room, any flimsy surface, such as clothing, will be vibrating. This modulates the radio beam reflected from the surface. Although the radio reflection that passes back through the wall is extremely faint, the kind of electronic extraction and signal cleaning tricks used by NASA to decode signals in space can be used to extract speech. Although, I doubt it would work in this room"
The Soviet KGB have been doing exactly this since before 1960. Windowpanes make good microwave reflectors. All it takes is a simple microwave source and mixer. Nothing new to see here.
Wouldn't the sound in the room vibrate the foil on the wall? Said foil would reflect microwaves very nicely, I suspect...
Max.
Funny thing is, with this kind of device tinfoil hats will actually improve "the black suits" reception, since tinfoil easily vibrates and reflects radiowaves really well.
*Sigh* what now?
J.
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When that happens, NO ONE can get to the page, not just those with lame firewalls.
[ObNerd]
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Even at 100GHz, the wavelength of microwaves is 3 mm. But sound waves inside a room would cause a surface to vibrate perhaps 0.001 mm. You cant modulate a 3mm wave to record 0.001 mm changes.
Interference detectors, more commonly known as interferometers, can detect distances far below the wavelength used to make the measurements. For example, 800 nm infrared laser light can readily be used to resolve 5 nm differences (I've worked on the development of such a system). Further, the distances being considered for measuring the movement of things like clothing or the throat and chest of the speaker are far above one micron (0.001 mm): put your finger on your throat and speak; think that's one micron you're feeling?
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