What are the Main Parts of a Communications Satellite?
Most communications satellites have the same basic components, pointed out in this diagram:
Solar cells and batteries to power the satellite systems
Antennas to receive and transmit signals
Transponder to alter the frequency of incoming signals (avoiding interference with outgoing signals) and to amplify signals before transmitting them back to Earth
Orientation and propulsion systems to keep the antennas pointed at Earth, and the satellite in the right orbit.