Radio whiz Greg Charvat just published this video showing off a very cool experiment with the low-cost coffee can radar system he and co-workers developed, in the fall of 2010, for MIT’s open courseware initiative.
In the video, Greg describes and demonstrates a simple circuit that causes a red/green LED on the receiving antenna to glow one color when the amplitude of the received wave is positive, and another when it is negative. Moving the LED back and forth in front of the transmitter, while taking a long-exposure photograph, gives a visual map of the wavefront in space. Impressive! [Thanks, Greg!]