ProxLF coil question

I installed the ProxLF onto my Proxmark3 earlier, and I tried to read a credit-card-sized tag with it to see if it worked. It seemed to couple rather poorly with the card, but I guess it’s because it’s meant to couple well with another coil rather than with a flat spiral antenna. Is my assumption correct?

That would make sense - I have the same observation. Been using my old Elechouse PM3 for cards/fobs and new RDV4 exclusively for implants.


Well, I suppose I answered my own question: I cloned a LF card into my yet-to-implant xEM chip through the needle, needle cap, syringe bag and DT’s plastic bag packaging without any issue whatsoever.

I get a solid read 1 cm away from the outer plastic bag provided the needle is parallel to the ProxLF coil and the needle’s bevel faces the coil. If the bevel faces away, I have to stick the coil right against the bag. So interestingly, that particular variable matters a lot more than I would’ve expected.

As for the oversize (13 x 3 mm) EM4200 chip that’s already in my right hand, I can read it from a good 3 cm away.

The ProxLF is quite a performer, that’s for damn sure! I just wish a 1.3-mm hex wrench was included in the package to undo the Proxmark’s screws. Or maybe it should be included in the Proxmark’s package… At any rate, I had to dig for that tool in my pile of junk.

My RDV4 kit came with the wrench and it promptly broke trying to unscrew original antenna :joy:

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Ah yes, I rechecked the box my Proxmark came in and found the tool at the bottom, under the foam pad thingy, in a baggy containing spare screws and a guitar pick also. Nevermind then :slight_smile:

My screws were only finger-tight.


Lucky, my screws felt like someone put locktite on them.

@amal: here’s a suggestion: a 13.56 MHz antenna you can run alongside the ProxLF coil. Or even better, a combo ProxLF / NFC antenna. And while we’re at it, a nice 2-piece plastic cover for it - although I realize that’s pretty unlikely :slight_smile:

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Discussions have already been had :slight_smile: no eta of course.


Still relatively new here, more lurking than anything :wink:

The products page says that the Proxlf is exclusively for the rdv4. I have the rdv2 and the easy. It it no at all possible to use with the rdv2? Or, just a pita to make work? Just curious…

Added question, any idea when it might be back in stock? Silly me didn’t think to order one and now, of course, there are none to order!

First off, your username is fucking great. Secondly, you can’t make the ProxLF antenna work with the rvd2 or the easy unless the Inductance of the LF coil is exactly the same as the rvd4 because of tuning for the resonant frequency (125kHz). The capacitors on the board are different, ergo different Inductance


13.56? :thinking: the HF caps affect the LF circuits? Or, just an uh oh on the typing? haha
But, I’m tracking what (I THINK) you’re saying. Antenna’s being plug and play for each respective revision not necessarily holding true between diff revisions. Well fuck…
Thanks for the username :blush: I get all kinds of shit on xbox live for it!

Yeah, that was a fumble with the frequency. You could measure the inductance of your proxmark antennas with a $40 LCR meter, and if they happen to be 203μH (the inductance of the ProxLF) then you could just drop it in. I highly doubt they’ll match though. Every little bit off of the target inductance value will dramatically affect tuning of the resonant circuit created. You can check out more about it here, if you’re interested.


Kudos for that! I’m more of a “how does it do what it does” kind of guy. I suppose that’s why we’re all here, anyways!
Looks like I have a bit of homework to do. Thanks again

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There’s one more wrinkle though… the RDV4 modular system puts the tuning caps on the antenna not the main board… this allows for different performing antennas to be made and easily swapped out, while the rdv2 has it’s tuning caps on the main PCB… so if your rdv2 antenna did have an inductance of 203μH you would still not be able to drop the ProxLF on the rdv2 because the caps on the proxLF antenna itself would change the total capacitance involved and skew the required inductance to match up at 125kHz.