Buying the xEM Access Controller Antenna

Hey is it possible to just buy the antenna by itself so i can buy about 3 to attach to a reader / cloner. wouldnt that solve the problem of the corruption?


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Sorry no… the access controller was originally made for a vehicle by an automotive manufacturer. Since the access controller is no longer made, I can only get units from a vendor who has access to a stockpile of these units, and cannot get just the antenna.

@TomHarkness and I are working on a possible new antenna design for the proxmark3 which will couple well with the xEM, though there is no ETA at the moment.


Amal can you still get the v1 access controller???
I’d love to have a second or third if possible

As far as I am aware, Amal only holds stock for replacement if required.
I believe he had problems with his supplier and the and the quality of product toward the end.

I think that’s why Amal sourced the V2 as an alternative.

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Thanks @Pilgrimsmaster for the update.
I am looking for a second antenna so that I can locate one on the handlebars of my motorcycle and then use either hand to start my bike.
I already have v1 installed in my bike near my left leg and am thinking that a handlebar mount would be a good second location. With my bike I’m sure that both antennas wont be inputting at the same time so that wouldn’t be an issue for installation

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If you mean having multiple antennas connected to the one xAC, it would still be a problem. Putting 2 coils in parallel would mess with the inductance and de tune the circuit. You’d have to go two entire xACs with diodes on their outputs.


Yeah that’s right putting two antennas on the reader would be a problem. However, a simple multiplexing solution like an SP ST manual switch could work very easily. Switch the center core of the antennas and leave the grounds connected together and you should be good. If you put that switch in the center of your handlebars for example, you could switch sides easily and it should work okay.

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I have one…
I can’t use it on my car - too new and if it were possible, I will loose my insurance.
So i can trade him.

You might look on ebay too. For awhile they were all over it. They had the same issue that Amal had. They were old stock being repurposed, and the stockpile dwindled down until the last ones were kinda crappy. Still, you might be able to score one, and scavenge the antenna.

Or you could have two coils with half the inductance in series. You’d half the signal but there’s a good chance the chip would remain readable. Some experimenting might be required to find the ideal coil size though.

Not unless you also add a capacitor to balance out the inductance of the second coil. Since the resonant frequency is based on an inverse square root relationship, a small change makes a big difference.

Specifically, for formula for calculating the resonant frequency of a LC circuit is:
f = 1 / (2π √L C)
Where: f is the resonant frequency in hertz (Hz), L is the inductance in henries (H), C is the capacitance in farads (F), π is Pi.

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Sorry maybe I wasn’t clear: I meant two coils in series, each with half the inductance of the one single coil they replace.

1 / (2π.√(Loriginal.C)) = 1 / (2π.√[(L1 + L2).C]

What are we talking about here?

I think I must be speaking Chinese or something :slight_smile:

Rajaramjet said he wanted 2 antennae on his motorcycle, Amal said no-go, that he needs to install a switch to use one or the other, and I say use two coils in series with a total inductance equivalent to the original coil (or half the inductance per coil, assuming they’re identical) with shite performances per coil, but perhaps good enough to work anyway.

Hmmm. That’s interesting. I don’t think it will work, but I’ll try it out and get back to you.

Well, if it doesn’t work, all it costs is a few feet of enamel copper wire and an hour of experimenting :slight_smile:


Ugh. I can’t pursue this. LF coils are really high inductance. Sorry.

Suffice it to say, dividing an inductor will not work at HF and maybe possibly might work at LF but probably not. 1 inductor =/= 2 half inductors in series when there’s a length of wire in between.

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That was just the general idea. Of course the final thing should have the right inductance, extra wires included.

I’ll have a play with it tomorrow at the office if I have some time.

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