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I finally told my buddy his 'phone detector' idea was pointless

He kept going on about this circuit he saw online that supposedly detects active cell phones hidden in a room. I asked him how it's different from just listening for a buzz or watching for the screen light up, and he got quiet. Has anyone actually built one of those things that works better than plain common sense?
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4 Comments
aaron_perry
The "detects active cell phones" thing is a little misleading since most of those circuits just pick up radio interference from any transmitting device, not specifically a phone. Your buddy's idea would probably work fine for finding a phone that's actively sending data, but it's gonna give false positives from wifi routers, bluetooth speakers, and even some microwaves. Honestly, listening for a buzz or watching for the screen glow is way more reliable for spotting a phone someone's trying to hide.
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the_leo
the_leo19d ago
Three microwaves and a toaster say hello.
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christopherh79
See it a little different myself. @the_leo, that approach can be useful in a pinch, but the false positives get annoying fast when you're in a room full of electronics. A simple RF detector is cheap and does a better job of filtering out all the random noise from standard appliances.
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alicecraig
alicecraig20d ago
False positives from microwaves" - classic.
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