[Problems with rational resampler]

gnuradio and vm sound like a bad combo, probably should just run it live and save files to disk. you'll run into USB trouble, I guarantee it. All the os calls on both host and virtual machine are going to slow down any communication you have between devices and you're going to get larger delays on something that's trying to run realtime.

[Problems with rational resampler]

I feel your pain. I've gotten into SDR quite a bit lately and ran into filter issues also.

http://greatscottgadgets.com/sdr/4/

Helped a lot for gnuradio specifics.

If I remember right, basically in a filter in gnuradio, the ratio between sample rate and frequency is what really matters.

[frequencies for keyfob or rfid cards?]

I haven't done much from 2009 on RFID but this is where I started http://www.openpcd.org/OpenPCD_Passive_RFID_Project

[frequencies for keyfob or rfid cards?]

defaultzero, fasttrack uses a mifare based system for RFID, it's actually really broken and easy to duplicate but I'd recommend not doing it.

snubs, thank you!!!! I've been using nothing but gnuradio for everything and that site opened up a whole new set of ideas.

[frequencies for keyfob or rfid cards?]

315 Mhz for American Automobiles is the communicating freq. It was fun to watch the fft bounce around.

[frequencies for keyfob or rfid cards?]

I too, am interested, I'll let you know if I have any luck with my car =D.

[New hackrf... getting phantom broadcasts.... help....]

Try going to greatscottgadgets.com and follow his hackrf tutorial in the education section. Many devices did not ship with the latest firmware and yours probably needs to be updated.