Understanding orbits can be called the key to understanding satellites. These videos by Nanosatisfi cover many facts about orbits.
Watch Coding For Space – Orbits 1
This second video about orbits covers the math involved in calculating a pure circular orbit.
Watch Coding For Space – Orbits 2
Physics Classroom: Mathematics of Satellite Motion http://www.physicsclassroom.com/class/circles/u6l4c.cfm
PLAN-13 Satellite Position Calculation Program by James Miller G3RUH