Problems with RFID sniffing due to bad driver?

I've now started to write some code for the ICAO MRTD LDS and PKI. If you know what that is, stop reading here. If you don't know: It's the crypto and data structures that are going to be present on the new "RFID passports" that will be issued in Germany (and elsewhere) soon.

Nothing seemed to work. Then it turned out to be a driver issue with the Omnikey 5121 proprietary Linux driver. Did I tell you that I hate proprietary software, especially drivers? Well, I'm on my way to re-implement that driver (actually, a generic Philips RC632 driver), too. But I better wait until it works before I start to re-implement the broken one...

So getting back to our RFID sniffing tests, I think the card was probably not even transmitting as expected. All the responses we got from the driver were bogus. This obviously results in no sub-carrier being broadcasted, and would explain why it was impossible for us to catch it in the spectrum analysis.