The uplink frequencies (5.9-6.4 GHZ) are used for transmission from the earth station to the satellite and down link frequencies (3.7-4.2GHZ) are used for transmission from the satellite to the earth station. The uplink frequencies are converted to lower frequencies by the mixer and local oscillator. The satellite acts as a repeater station; it receives the signal, amplifies it and then transmits over the next frequencies to avoid interference between the uplink signal and down link with the help of transponder. Satellites with   multi transponders have increased over the year.