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#1 2011-12-19 10:25:06

vivat
Contributor
Registered: 2010-10-26
Posts: 332

Need help building long range LF antenna!

I'm trying to build long range antenna for proxmark. The dimensions are 30*30 cm, enamelled cable is 0.13 mm. What's wrong?
longlf1.th.jpg

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longlf2.th.jpg

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hw tune
#db# Measuring antenna characteristics, please wait.       


# LF antenna:  2.42 V @   125.00 kHz
# LF antenna:  2.42 V @   134.00 kHz
# LF optimal:  2.82 V @   400.00 kHz
# HF antenna: 13.44 V @    13.56 MHz
# Your LF antenna is marginal.
#db# Measuring antenna characteristics, please wait.       


# LF antenna:  2.42 V @   125.00 kHz
# LF antenna:  2.42 V @   134.00 kHz
# LF optimal:  2.69 V @   375.00 kHz
# HF antenna: 14.37 V @    13.56 MHz
# Your LF antenna is marginal.
#db# Measuring antenna characteristics, please wait.       


# LF antenna:  2.42 V @   125.00 kHz
# LF antenna:  2.42 V @   134.00 kHz
# LF optimal:  2.82 V @   387.10 kHz
# HF antenna: 14.37 V @    13.56 MHz
# Your LF antenna is marginal.
#db# Measuring antenna characteristics, please wait.       


# LF antenna:  2.42 V @   125.00 kHz
# LF antenna:  2.42 V @   134.00 kHz
# LF optimal:  2.82 V @   387.10 kHz
# HF antenna: 13.05 V @    13.56 MHz
# Your LF antenna is marginal.

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#2 2011-12-19 10:44:24

rule
Administrator
Registered: 2008-05-21
Posts: 416

Re: Need help building long range LF antenna!

Pretty impressive for a high frequency antenna I would say wink

Did you connect the correct wires?
Green/Black for HF
Red/White for LF

Cheers,

  Roel

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#3 2011-12-19 10:52:59

vivat
Contributor
Registered: 2010-10-26
Posts: 332

Re: Need help building long range LF antenna!

roel
I use hirose mq172 connector, not the cable.
Yes, my home-built HF antenna works good. It helps me hack many tags. But I have trouble with building long-range LF antenna.
The resistance of this antenna is 181 ohms, mine home first close-range LF antenna have 49 ohms:
http://www.proxmark.org/forum/viewtopic.php?id=756

Last edited by vivat (2011-12-19 11:01:37)

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#4 2011-12-20 13:51:02

Cex
Contributor
Registered: 2009-12-14
Posts: 104

Re: Need help building long range LF antenna!

Hello,

0.13mm for an antenna reader looks too thin.
I'd try with at least 0.2mm to reduce ohms.

On the other hand, did you use the correct number of turns to get the proper L value?
It looks like your antenna is detuned.
Try adding/removing some turns, or put a capacitor in parallel with the antenna to check if your results get better or worse.

Regards.

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#5 2011-12-20 18:41:34

vivat
Contributor
Registered: 2010-10-26
Posts: 332

Re: Need help building long range LF antenna!

Hi there
OK, I'll try another cable.

On the other hand, did you use the correct number of turns to get the proper L value

Nearly 90-100 turns. I have tryed to add/remove few turns, this didn't helped. What do you mean "proper L value"? Inductance or what? What cap should I solder?
BTW I have downloaded a nice RFID design guide from Microchip:
http://ww1.microchip.com/downloads/en/d … 51115f.pdf
I have found that HID's 5375 long-range LF reader eats lot of energy:
Current Requirements:
DC Current at 12V: Avg. 200mA, Peak 700mA
DC Current at 24V: Avg. 260mA, Peak 1.2A
Some chinese reader from:
http://store.infotronicx.com/Products/3 … india.aspx
Power Requirements       18V to 19.2 V DC
So I have another question-do I need amplifier or something for long-range antenna?

Last edited by vivat (2011-12-20 18:50:32)

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#6 2011-12-21 08:26:54

Cex
Contributor
Registered: 2009-12-14
Posts: 104

Re: Need help building long range LF antenna!

Yes L is inductance.

To calculate the inductance of your antenna use the EQUATION 26 on page 59 of the Microchip document you are referencing.
For the antenna to be properly tuned it shall conform to the equation  f=1/(2*PI*sqrt(L*C)), taking into account that f=125000, and C is the value of C43 of your Proxmark (usually 1nF).
For 1nF -> L=1.62mH

Regarding the high power on antenna, you should take into account that having a big antenna will enable you to capture card response more easily, but the main constraint on low frequency tags is that you need to generate a field strong enough to power up the tag, and the generated field decreases proportionally to the square of the distance (Check pages 49 to 56 of the Microchip doc, it is explained there).
As the generated field is proportional to the current on the reader antenna the comercial readers usually use quite a thick wire and high current drivers for the coil.

If you don't use an amplifier for proxmark3 you'll surely won't get a high reading distance, but surely better than smaller antennas.

Regards.

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#7 2011-12-21 15:24:05

Bugman1400
Contributor
Registered: 2010-12-20
Posts: 132

Re: Need help building long range LF antenna!

Whoa.......I just had a flashback to my college days in Physics class. I never want to do that again.

Good post.

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#8 2012-03-02 19:56:24

Raymond
Contributor
Registered: 2011-09-14
Posts: 30

Re: Need help building long range LF antenna!

Hi Vivat,

Did you purchase the INF LRRFID 125Khz Long-Range RFID Reader and connect it to PM3?
From http://store.infotronicx.com/Products/3 … india.aspx

If yes, Does it work?

Looking for long range antenna for LF & HF tags.

Regards

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#9 2013-04-23 10:06:34

Leif
Member
Registered: 2012-11-21
Posts: 1

Re: Need help building long range LF antenna!

Maybe anybody done long range antenna and had circuitry of amplifire for it?
I have done big antenna, but range of read is about 5 cm for HID

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#10 2013-04-23 14:41:34

vivat
Contributor
Registered: 2010-10-26
Posts: 332

Re: Need help building long range LF antenna!

Hi
Unfortunately pm3 wasn't designed to use long range powerful antennas because of it's buffers(IC9, IC10).

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#11 2013-04-23 22:00:46

0xFFFF
Administrator
From: Vic - Australia
Registered: 2011-05-31
Posts: 505

Re: Need help building long range LF antenna!

NXP application note AN103510 and Maxim application note 2768 cover RF amplifiers. But I do not know if the referenced designs are in any way suitable for the Proxmark.


modhex(ecijhhhhhhhhfchdhbidhniihghdduhehvhtduhbig)

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