Build your own Synthetic Aperture Radar
An inspiring story, about someone who build his own radar from scrath.
In this movie Michael Scarito describes the different forms of radar, his own prototypes, and shows that you can build a radar with simple components like cofffeecans, mini-curcuit modules. His first prototype worked with a soundkaart and PC, but he found it to be too limiting because you only see the objects when they are 7 km away.
He is working on radar at MIT: http://www.ll.mit.edu/mission/space/imagingradar.html and works together with another radar builder, Gregory Charvat. Gregory build several radar systems, like the 240 dollar radar and a doppler radar.
You can find his radar building course a MIT.