Q.What is a transponder?

A communication satellite must both receive a signal from Earth and send one back down, and the single unit inside it that does both has a specific name. …

[!TLDR]

A transponder is the receiver-transmitter unit in a satellite that amplifies the received signal and re-sends it on a different frequency.

The transmitter-receiver combination carried in a communication satellite is called a transponder. Its two functions are amplification and frequency translation. Frequency translation is necessary because the satellite cannot receive and transmit on the same frequency without interference. A transponder has a wide bandwidth but is normally used for only one uplink and one downlink signal to minimise interference and improve reliability, which is why a communication sa …