full screen (high res) http://images.tinypic.pl/i/00765/8g7j8biccn4d.jpg [Broken] Em Wave = LIGHT Em Wave = Radio Equator Source------L---------Sensor How big L we need use to register Doppler ? I wan to measure 360/24h speed Big Question ?! single arm we have Doppler (RED ) [ more long arm ---> more deep RED ] 4 Arms and we have ZERO ???? how it works ? can You explain me this by math !? Thank You for solve above problem ( i want to build singnle arm to measure 360/24h ) can I do this in Home ?