3 ms·

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

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.

diggan 2y ago
> 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?
- hoistbypetard 2y ago
  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.
- mannykannot 2y ago
  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 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-century-ago/ https://hackaday.com/2022/04/20/copper-rectifying-ac-a-centu...
gorjusborg 2y ago
> 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.
- Teever 2y ago
  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/ https://www.morerfid.com/uniqlo-rfid-tags/
- nullc 2y ago
  it's not just electronics cause positives-- corroded metal does too, anything that forms a semiconductor can get detected.

diggan 2y ago

> 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?

hoistbypetard 2y ago
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.
mannykannot 2y ago
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 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-century-ago/ https://hackaday.com/2022/04/20/copper-rectifying-ac-a-centu...

gorjusborg 2y ago

> 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.

Teever 2y ago
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/ https://www.morerfid.com/uniqlo-rfid-tags/
nullc 2y ago
it's not just electronics cause positives-- corroded metal does too, anything that forms a semiconductor can get detected.