For about $250, you can make your very own space-age spy tech, following an MIT professor's instructions.
It can capture high-resolution images of small objects -- like a message written in push pins that had been hidden behind a foam plate.
Using a garage-door opener, microwave parts and a cordless drill, Gregory Charvat made a working synthetic aperture radar (SAR) system, the same kind of technology the military and NASA use. Charvat used algorithms to combine the back-scattered radar images into a high-res photos of things in his garage, like a Cannondale bike and a model F-14.
SAR is useful because it combines multiple radar images to create higher-resolution images than would otherwise be possible. There are a couple ways to do it -- by using a single antenna on a moving object, like an airplane or spacecraft, or by using multiple small antennae scattered over a large area. NASA uses SAR to create detailed maps of other planets, and it can be used to map the spread of oil in the Gulf of Mexico, for instance.
Charvat notes that developing new SAR algorithms is difficult because the technology is so expensive. But his system is cheap: It's a frequency-modulated continuous wave radar with a homodyne radar architecture, made from a discarded Genie garage-door opener and an old microwave.
"This system could easily image objects as small as pushpins and 4.37 mm diameter steel spheres," he notes on his Web site.
Granted, his $250 price tag doesn't include the computer you'll need to drive the device. But ingenuity is priceless.
Great idea but I think that messing around with an old micro wave oven is very dangerous. In fact in the UK it is probably illegal.
Okay...how about how to build the surface to air missile I'll need to defend my backyard? Come on, how can you only give instructions for making a radar but not the anti-aircraft missile that's supposed to go with it?
Actually, an old magnetron is useful for all kinds of neat stuff, and most of them are simply a matter of loading up your Open Source free software so you can tell what your wavelength is doing and affect it accurately. It's all radio, people, even the drill and the door opener. Thanks, MIT, for this, and the KERBEROS project.