szczys writes "Gregory Charvat has been playing with and teaching others about entry-level radar concepts for a long time. Now he's sat down and explained how you can do it yourself inexpensively. He says, 'One enabling technology for Radar was the cathode ray tube (CRT), which facilitated a method of measuring the time delay between transmitted and received waveforms. ... Today, rather than using a CRT we can use high-speed digitizers. This offers the obvious advantage of applying signal processing to acquired data so that only moving targets are detected, tracking can be achieved, imaging, and a multitude of other modes. But for hobbyist and consumer projects we do not need this much power, range, and can not afford the cost. We need the ability to sense like a long range radar (detecting only moving targets, imaging, Doppler, signatures, etc) but at short ranges and at low costs.' Charvat then proceeds to walk through several options for the amatuer hardware hacker."