Comment by hoistbypetard
1 year ago
Yeah!
It also makes me suspect that the device would not be super-useful in most environments today because our homes and offices have false positives littered all over the place. Such a countermeasure would be unnecessary now.
> our homes and offices have false positives littered all over the place
Sure, but location matters. Searching weird (for electronics to be), but line-of-sight places (like a bookcase) you might still have a good signal to noise ratio.
Now you've got me wondering how common embedded RFID price tags are.
As I understand it clothes from Uniqlo have RFID tags in them.[0]
https://www.morerfid.com/uniqlo-rfid-tags/
it's not just electronics cause positives-- corroded metal does too, anything that forms a semiconductor can get detected.
> useful in most environments today because our homes and offices have false positives littered all over the place
Like the structural elements in your house/apartments have something similar to diodes in them, or what are you referring to?
I had a vague recollection that rectifiers for battery chargers were once made out of stacked layers of oxidized copper disks, and then, in the article danbruc linked to, I saw this:
Note that other semi-conducting materials, such as a rusty nail or an oxidised piece of metal, also generate harmonic frequencies and may therefore cause an NLJD to generate a false positive.
https://www.cryptomuseum.com/df/tscm.htm#nljd
It turns out that the rectifiers in question were copper - cuprous oxide - lead sandwiches:
https://hackaday.com/2022/04/20/copper-rectifying-ac-a-centu...
I think a lived-in place has enough stuff in and near the walls to make this kind of scan less than useful. We have things hanging on the walls that'd distort it. Maybe an empty one would be OK now, but I think the ecobees all over the place would even distort it for those.