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EMP
Have you tried to use Google? The first find is a very good instruction.
http://www.instructables.com/id/How-to-make-an-EMP/?comments=all
Greetz NoPax
An EMP… for what? If you want one (relativity) free, just throw a rope over the power lines and pull. If you have an RFID in you, that thing will be toast.
If it's cheap, like $4, then that means it's probably made with household items. Meaning the materials will also be basic (like a Polaroid camera, or old microwave, etc). Meaning, you have to understand the concept first.