Mark Dain @eric: What would you recommend if I wanted to buy two cheap SDR's (Mac compatible would be ideal, otherwise Linux support). I'm interested in sending some packets between two computers on a makeshift radio. Just for fun, so I don't need a ton of bandwidth but I basically need raw I/O or very close to that if possible

Eric For receiving any RTL SDR will do (little USBs, just Amazon the phrase, should be PS15~), transmitting might be a little more costly. You could use one of those in-car FM transmitters, they're legal to use whereever since their range is all of 2 metres. Any more than that and transmitting is a legal and costly effort. By in car transmitters I mean something designed to take an aux input and put it on whatever FM frequency, so you can aux with an old car radio. Those are about PS10 from Argos. If you need links drop me another mention and I'll get onto the desktop and put together something more coherent.