(*****) ProxLF antenna for the Proxmark3 RDV4

Pilgrimsmaster · January 19, 2021, 8:45am

ProxLF antenna for the Proxmark3 RDV4

Most of this info comes from the DT webpage, but some more info added for the review.

The ProxLF antenna is finally here! Designed exclusively for use with the Proxmark3 RDV4, this 125kHz “LF” antenna is so powerful, it can talk to our 125kHz implants like the xEM and NExT from 2cm away! In some cases it can even talk to the xEM while it is still inside the injection assembly needle!

SOURCE

Dangerous Things, KSEC, Sneak Technology, Hacker warehouse, Lab401, eBay

CAPABILITY

125kHz xSeries implants (xEM, NExT)

Dangerous Things 125kHz x-series implants like the xEM and NExT contain the T5577 chip, which is capable of emulating many different types of 125kHz ID chips including EM41xx, EM42xx, HID ProxCard, Indala, AWID, and others. However the T5577 chip does not support tear protection, so if you attempt to change the configuration of the T5577 without a good coupling (i.e. a good matching antenna on the reader), it’s possible to “brick” the chip so it will not communicate properly.

The ProxLF is specially designed with a cylindrical inductor that shapes the lines of magnetic flux to perfectly couple with the small cylindrical antennas inside the xSeries chip implants!

ONLY COMPATIBLE WITH RDV4 –

*The ProxLF antenna is specifically designed for use with the Proxmark3 RDV4.

The design of the RDV4 version of Proxmark3 allows for modular antennas, which places the tuning capacitors of the antenna network on the antenna module.

It is not possible to use the ProxLF antenna with any other version of Proxmark3

The ProxLF is made specifically for the RDV4, but there is no specific case made for it, But there are some community mods worth considering

HERE for the guide

PROs

Tuned for xSeries
Modular antenna connections
“Cheap”

CONs

Limited to RDV4 only

PRICE

$35

Summary:

Designed and made specifically for Dangerous Things LF xSeries implants, and is a modular antenna that can be swapped in and out at will.

Reduces the chances of bricking your implant.

Tuned for xSeries but still works with cards and likely LF Flexies

Well priced and a capable add on to the RDV4

Rating by the community

PLEASE ONLY VOTE IF YOU HAVE ONE OR HAVE USED ONE

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ProxLF antenna 1-5

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0 voters

neintynein · July 7, 2022, 2:09pm

Can we strip the antenna out to use with the pm3 easy?

Pilgrimsmaster · July 7, 2022, 6:06pm

Not that simple unfortunately

Here's why

Frankenstein the xEM access controller for proxmark proxlf

To further clarify why borrowing an antenna probably won’t work;

Normal radios like cell phones, wifi, etc. are all “EF” emitters… they emit waves of electrical potential across the electric field. Those types of antennas are simply unshielded conductors, and they are “tuned” to a frequency by adjusting their length to best match a harmonic of the wavelength of the radio frequency being transmitted (or received). That means if you take one 2.4ghz antenna from a wifi router and attach it to another 2.4ghz wifi router, the length of that antenna is correct and you’re good to go. This is where the idea that you could use one 125khz antenna from one reader with another comes from, but sadly it’s not correct.

With EF transceivers, length of the emitter (antenna) is what “tunes” it for a specific frequency. Some 2.4ghz antennas are longer or shorter based on the harmonic;

As you can see from the chart above, 2.5ghz has a full wavelength of 12cm, which is about the length that most “rubber ducky” antennas hanging off the backs of wifi routers are… but sometimes you see shorter “stubby” antennas, which are going to be a “harmonic” of the full wavelength… usually 1/2 or 50% wavelength, or 6cm.

Anyway, the point is, EF transmissions are all about electric field potentials. That is not how magnetically coupled devices like passive RFID transponders work at all. In fact, the only reason we use the term “antenna” to describe what are essentially two inductor coils (one used by the reader and one for the transponder) is that they happen to be moving both power and data across a shared magnetic field. Normally when you are placing two inductors near each other in order to move power alone, it’s called a transformer .

To get an inductor “tuned” to a specific frequency, you are basically building a L/C circuit that resonates at your target frequency. In an LC circuit, your inductor (L) has an inductance value which must coordinate with your capacitor ( C ) in order to resonate at a specific frequency. So, you can have basically a nearly infinite number of combinations of L values and C values that all resonate at 125khz. The lower your C value, the higher your L value must be to maintain 125khz tuning. Because it requires two values to match in a specific way, there is absolutely no guarantee that the C value used by the access controller (which dictates exactly what L value the “antenna” must have) will match the C value of your proxmark3… and if your proxmark3 has a different C value, then the L value required to resonate at 125khz will not match the L value of the antenna from the access controller

But these may be of assistance in making your own

neintynein · July 7, 2022, 7:02pm

hell yeah, thanks for the effort!

This is a pretty good community