Crazy Simple 40m Transciever: MOSQUITO Minimalist Transceiver
This 40m transceiver only has around 16 parts, and only a single active device: the ubiquitous IRF510 power transistor which you can even get at Radio Shack. Okay, it’s not exactly a complete receiver: they wired it to a PC sound card, and run an SDR application to get receive audio, but still, impressive!