Just a quick note. I have been meaning to try out the combination of the Raspberry Pi with one of the popular $20 RTL-SDR dongles, to see if the combination would work. I was wondering how well it would work, how hard it would be, how much of the available (small) CPU power it would use. The short answers: reasonably well, pretty easy, and maybe 20% for rtl_fm. That’s pretty encouraging. I’ll be experimenting with it some more, but here’s a short bit of me recording KQED, the bay area PBS FM station, using the pitiful tiny antenna that came with the dongle. It should be noted that my house is in a bit of a valley, and FM reception in general is quite poor, and I recorded this from inside my house, which is stucco and therefore is covered in a metal mesh that doesn’t help. Not too bad. I’ll work out a better antenna for it, and then try it more seriously.

Addendum: Here is a page with lots of good information on RTL-SDR/dump1090 on the Raspberry Pi.