📘 Definition
A transponder (transmitter-responder) is the core payload element of a communications satellite. It receives signals from ground stations on the uplink frequency, amplifies them, shifts them to the downlink frequency, and retransmits them. Modern satellites carry multiple transponders, each covering a specific frequency band (C, Ku, Ka, or V band) and bandwidth. Transponder capacity is leased or sold to customers (TV broadcasters, telecom operators, internet providers). A typical GEO comms satellite carries 24–72 transponders with a total throughput of 10–200+ Gbps.
Receive → amplify → retransmit
Function
C, Ku, Ka, V
Bands
24–72 per GEO sat
Typical Count
Leased capacity ($/MHz)
Revenue Model