Proxmark developers community

Research, development and trades concerning the powerful Proxmark3 device.

Remember; sharing is caring. Bring something back to the community.


"Learn the tools of the trade the hard way." +Fravia

You are not logged in.

#1 2010-03-09 03:43:06

terrizzi
Member
Registered: 2010-03-05
Posts: 4

ripped antenna from HID reader

thought it could just hook it up since HID makes readers, but my vaules are all screwy.

# LF antenna:  6.18 V @   125.00 kHz
# LF antenna:  6.31 V @   134.00 kHz
# LF optimal: 40.82 V @   203.39 kHz
# HF antenna:  0.10 V @    13.56 MHz
# Your HF antenna is unusable.

any ideas,  remove some coils?

Offline

#2 2010-03-10 02:13:55

terrizzi
Member
Registered: 2010-03-05
Posts: 4

Re: ripped antenna from HID reader

well removing coils just make it worse.

Offline

#3 2010-03-10 04:46:34

d18c7db
Contributor
Registered: 2008-08-19
Posts: 292

Re: ripped antenna from HID reader

Generally removing coils from an inductor reduces its inductance making it resonate at higher frequencies. As your inductor already resonated at over 200Khz, removing coils shifts it in the wrong direction, you want to add instead.

I don't know if it's too late and if you could put those coils back on but since the software tells you the resonant frequency of the coil you could use that to calculate a new C capacitor value that would shift the resonant frequency down to 125Khz.

F=1/(2*pi*sqrt(L*C))

You know the current F (203Khz) and the C, solve for L
Once you know the L solve for C at 125Khz and find the new optimal C value....

Last edited by d18c7db (2010-03-10 04:50:31)

Offline

Board footer

Powered by FluxBB