[Jeri Ellsworth] is at it again, this time*she takes apart a hot*wheels*speed gun and in the process she does a good job of *explaining*how radar can be used to measure speed. *She also demonstrates a way to determine if an object is*approaching*or*receding*from the radar gun.
The*Doppler shift is one way to remotely measure the speed of an object. It works by*measuring*the change in frequency of a wave after it strikes an object. Rather than measuring the*Doppler*shift of the returning wave most radar guns use the phase shift. The reason is that the frequency shift of a relativly slow object (60mph), to a relitivly high frequency signal(10GHz) is small (about 0.893Hz), where the phase shift*varies*based on the distance of the object. *This is all just a stepping stone in her quest to build a crude TSA body scanner.
Filed under: radio hacks, teardown, toy hacks
