As some of you may know, I've recently started to get more into electronics (again). It's been more than seven year since I finished my training as radio communications technician :)
Anyway, I wanted to do some research with regard to passive RFID sniffing, DECT (in)security and other subjects. You can build digital receivers the old-fashioned way: RF, Oscillator, Amplifier, Mixer, IF and Demodulator in hardware. This is what we all know and love ;)
However, recently so-called "software defined radios", a technology that was only available for government services and military (aka big money), are becoming cheaper and cheaper. Software defined radios take the complex IF signal and digitize it with high-speed A/D converters. All demodulation or other further processing can be done by signal processing software on the PC.
To my very big surprise, the Gnuradio project is already providing a very flexible python-scriptable software for doing such processing. Available code for demodulation is still quite limited (e.g. no FM stereo decoding, and only very preliminary NTSC b/w decoding). But well, this is just a matter of time.
What's even more interesting is the USRP (Universal Software Radio Peripheral), basically a USB2-connected FPGA-board with high-speed ADC and DAC's. It's available for less than 500EUR, so I immediately had to buy one. It hasn't yet arrived (shipping from the US), but maybe that's actually better... since experimenting with it will definitely occupy a lot of time that I don't really have :(