ProxMark3 low voltage on lf and hf antenna ( < 23 mV ) No implant read

Hello guys !

I got implanted with a NExT about 3 weeks ago, swelling is not noticeable.
I just received my Proxmark3, and followed the tutorial from Amal, everything works correctly.

I started by cloning a HID card to a blank 125khz card and it worked perfectly.
Now i wanted to detect the 125khz chip of my NExT to clone this specific card to the chip.

I used the lf tune to get try and position myself correctly and saw that my max voltage was 10 mV below the average ( got max 24 mV )

I first isolated the Proxmark from my desk, then tried all my usb ports, checked with another cable and the voltage is still low.

I used the implant in epoxy to see if it shines and it does but the drop in voltage is unnoticeable ( < 0.100 mV )

I haven’t been able to scan my NExT 125khz chip ( only got 1 false positive with an Indala card )

I tried to scan my Spark2 and my 13.56MHZ chip on my NExT and also got no read from the ProxMark

I know for a fact that these 2 chip works since i can scan them very easily and at a good distance with both my phone and my keyboard wedge reader and use them pretty much daily.

It’s my first time tinkering with the Proxmark3 and 125khz chips, so i’m by no mean an expert and was wondering if maybe there is something wrong with my Proxmark or my NExT ?

It can be tricky positioning the proxmark3 over a NExT, especially when it’s implanted and hard to pin down exactly where it is under the skin.

First off, if you’ve not found this gem, I would make use of the delay command;

Now you have a fighting chance to properly position the LF antenna coil directly over the NExT.

When it comes to HF, it’s important to note that the actual HF antenna coil is on the bottom PCB, not the middle PCB which is what you see looking down at the top. If you look closely at the bottom PCB you can see the traces of the HF antenna coil running on the top side of the bottom PCB… basically sitting between the bottom PCB and the middle PCB. Because of this, you get much better reads of x-series implants if you actually just place the proxmark3 down on your NExT so the bottom PCB is resting with the antenna traces running perpendicular across your NExT.

Finally, the voltage levels do vary a considerable amount with every proxmark3. If your hw tune indicates both antennas are ok, then they should work just fine with the NExT when ideally positioned.