The ground station for ECOSat-II, responsible for communication between the ground and the satellite, is in its final stages of completion. The antenna being used is a large Yagi. Yagi antennas have very directional radio propagation that we can use to our advantage by pointing at the satellite.
Yagi Propogation 
That is why the ground station is equipped with an elevation and azimuth rotor that will be able to track any satellite that passes overhead. Satellites do not pass slowly though, and in a low-earth orbit (which is what ECOSat-II will be in), they travel around 7km/s. While their orbit is far enough away (~800km) that our rotor can keep up with them, another problem arises. Communication with satellites at these speeds will be heavily affected by the doppler effect. As they approach the frequencies get higher and after they pass they get lower. This can shift the incoming frequencies from 3kHz in the 2m band to 9kHz in the 70cm band .