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[Discuss-gnuradio] Re: RFID Capture

From: Michael Buettner
Subject: [Discuss-gnuradio] Re: RFID Capture
Date: Tue, 24 Feb 2009 10:41:44 -0800

Gen 2 (915 MHz) has read ranges measured in meters, while HF (13.56 MHz) range is measured in cm. Check out "How to Build a Low-Cost, Extended Range RFID Skimmer" for how to increase read range for HF devices; they got about 35 cm. But to answer your question, I just use a vanilla circular antenna which is pretty standard for Gen 2 applications. 


> Hello All,
> I'm trying to do more or less the same thing as Kevin but with two other
> readers (a RFIdeas Playback and an OpenPCD) and other kind of cards (HID
> IClass 2K and Mifare Classic 1K: both working at 13.56MHz).
> I got an interesting signal just putting my loop antenna attached both
> to the card and the reader: even if it is a bit weak, I can recognize
> the tag reply.
> (USRP 1, BaseRX with the usrp_rx_cfile.py -f 13560833 -r B -d 16)
> One of the problems I have is that I have to stay as much close as I can
> to the card to be able to read its response (from more than 3 inches I
> get an unreadable signal...), so I would like to ask Michael which kind
> of antenna (and any external things) you used to be able to read the
> signal from few feet away. Any suggestions will be very well appreciated.

> Thank you very much,
> Marco

> > Michael Buettner wrote:
> > Are you using the ThingMagic in monostatic mode (one antenna that does RX and
> > TX)? If so, you probably won't be able to see the tag reply. Further down the
> > receive path the ThingMagic has circuitry that removes the strong TX signal
> > leaving only the tag reply, but I assume you are tapped in before that. You
> > MIGHT have better luck if you use the reader in bistatic mode and tap in at the
> > receive antenna, particularly if you don't use the full 1W output power. Another
> > option would be to just put the USRP antenna near the tag, and receive both
> > reader and tag commands there. I have had pretty good luck with that, and can
> > decode tag responses from a few feet away.
> >
> >
> > michael

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