3 ms·

Would like to know where to get those $2 magnetic probes :o

Dwolb 11y ago
Honestly, just strip coax away the outer sheath to expose the inner conductor. Make a loop with the exposed inner conductor and solder back onto the sheath. Increase the loop size or turns for lower frequencies.
- friendzis 11y ago
  Stripped probe is electric. Looped probe is magnetic. Stripped/looped probe is mixed probe. If you use coax - leave the shielding, just make sure to leave a gap. Just look at this picture [1] from this quite good article [2]. Depending on the design/equipment, you might need balancing/symmetrization. Also directivity/sensitivity. While turn count will improve overall sensitivity, loop size will increase directivity. Keep in mind that both loop size and turn count affect probe filtering characteristics (it IS a filter), so I highly recommend experimenting with several designs. Have a look at my attempt at making magnetic probe from RG174 [3]. It is fat because of two layers of thermal shrink tube, which made it stiff enough for my experiments :) It is hard to tell from a picture, but it should be that this probe uses two wires exactly for this purpose: one acts as a central conductor, other as a shield. [1]: http://www.compliance-club.com/archive/old_archive/030718b.jpg http://www.compliance-club.com/archive/old_archive/030718b.j... [2]: http://www.compliance-club.com/archive/old_archive/030718.htm http://www.compliance-club.com/archive/old_archive/030718.ht... [3]: http://imgur.com/hiRUJl6 http://imgur.com/hiRUJl6
mrswag 11y ago
An RTL-SDR (6$ on ebay, get the R820T2) could work too.
- cnvogel 11y ago
  The RTL SDR can (unmodified) only receive down to a few ten MHz. At least for some of their research they used a soundcard. As far as I know you will access different types of information. kHz range is mostly power consumption. Tens/hundreds of MHz is bus activity. Both may be correlated, and both gives you side channel information to attack cryptography.
cnvogel 11y ago
To me it looks like the coil of an wireless charger, or of an RFID reader.
- y04nn 11y ago
  Yes, this is what you can find inside a wireless charging pad or inside a wireless charging phone. You can find them on ebay for $3. Look for "usb wireless pad".
duhast 11y ago
You can find it here: https://www.digikey.com/product-search/en/inductors-coils-chokes/wireless-charging-coils/197928 https://www.digikey.com/product-search/en/inductors-coils-ch...

Dwolb 11y ago

Honestly, just strip coax away the outer sheath to expose the inner conductor. Make a loop with the exposed inner conductor and solder back onto the sheath. Increase the loop size or turns for lower frequencies.

friendzis 11y ago
Stripped probe is electric. Looped probe is magnetic. Stripped/looped probe is mixed probe. If you use coax - leave the shielding, just make sure to leave a gap. Just look at this picture [1] from this quite good article [2]. Depending on the design/equipment, you might need balancing/symmetrization. Also directivity/sensitivity. While turn count will improve overall sensitivity, loop size will increase directivity. Keep in mind that both loop size and turn count affect probe filtering characteristics (it IS a filter), so I highly recommend experimenting with several designs. Have a look at my attempt at making magnetic probe from RG174 [3]. It is fat because of two layers of thermal shrink tube, which made it stiff enough for my experiments :) It is hard to tell from a picture, but it should be that this probe uses two wires exactly for this purpose: one acts as a central conductor, other as a shield. [1]: http://www.compliance-club.com/archive/old_archive/030718b.jpg http://www.compliance-club.com/archive/old_archive/030718b.j... [2]: http://www.compliance-club.com/archive/old_archive/030718.htm http://www.compliance-club.com/archive/old_archive/030718.ht... [3]: http://imgur.com/hiRUJl6 http://imgur.com/hiRUJl6

mrswag 11y ago

An RTL-SDR (6$ on ebay, get the R820T2) could work too.

cnvogel 11y ago
The RTL SDR can (unmodified) only receive down to a few ten MHz. At least for some of their research they used a soundcard. As far as I know you will access different types of information. kHz range is mostly power consumption. Tens/hundreds of MHz is bus activity. Both may be correlated, and both gives you side channel information to attack cryptography.

cnvogel 11y ago

To me it looks like the coil of an wireless charger, or of an RFID reader.

y04nn 11y ago
Yes, this is what you can find inside a wireless charging pad or inside a wireless charging phone. You can find them on ebay for $3. Look for "usb wireless pad".

duhast 11y ago

You can find it here: https://www.digikey.com/product-search/en/inductors-coils-chokes/wireless-charging-coils/197928 https://www.digikey.com/product-search/en/inductors-coils-ch...