[Discuss-gnuradio] Problems with the usrp_rx_cfile.py, usrp_fft.py and usrp_oscope.py and RFID signals

[Marco Bottino]

Hello,
I am a student and I am doing my thesis project on the RFID protocols.
At the present time, with the USRP, I am trying to catch the signal between a
reader and a tag RFID.
As reader I am using an OpendPCD (using the firmware for the Mifare Classic
protocol) and as card a Mifare Classic Card.

Because of I am a very beginner of USRP and all the rest, I am using the
programs usrp_fft.py and usrp_oscope.py and the usrp_rx_cfile.py program with
another program called Baudline to analyse the spectrum.

My problem is that I can easily see in the frequency domain, using usrp_fft, the
carrier at 13.561Mhz, but not the subcarrier that should be a 847KHz modulation
of the carrier (probably covered by noise) even if I try to use a baseRX
daughterboard instead of the LFRX. Moreover, in the time domain (with the
usrp_oscope), I cannot recognize anything interesting.

As it isn't enough, with the usrp_rx_cfile and the program baudline I cannot
recognize neither the carrier: my opinion is that it is caused by a wrongly
interpretation of the bit-length of the samples (and for this I should need a
confirmation that the output samples are 16 bit-length). That program supports
these formats: alaw ulaw s8 u8 le16 be16 le32f be32f. Does anybody know wich is
the format I should use?

Probably I'm using wrongly the hardware and the software I have...

Could somebody suggest me a solution? Any kind of help will be absolutely well
appreciated!

thank you,

Marco