Hub: A hub is a collection of communications equipment designed to receive signals from (and usually transmit signals to) satellites.  It is also called a downlink station

Today information is normally sent as digital signals from a ground station to a satellite. At the satellite, the signals are received, amplified, and as a rule converted into another frequency before they are sent back to another ground station.  The transmission of the signals takes place by means of parabolic aerials and microwaves with wavelengths from 1 - 20 cm.