Communications satellites: what is the term used for the multiple repeater units onboard a communications satellite that receive, shift frequency, amplify, and retransmit signals?

Introduction / Context:
Communications satellites carry several repeating units that listen to uplink frequencies, convert them to downlink bands, amplify, and retransmit toward Earth. Knowing the proper name for these onboard repeaters is basic to satellite communications, link budgeting, and transponder-leasing business models.

Given Data / Assumptions:

• The device receives an RF uplink and retransmits on a downlink band.
• It performs frequency conversion and amplification.
• Multiple such units exist per satellite to form distinct channels/beams.

Concept / Approach:
Each onboard repeating unit is called a transponder. Ground “stations” are on Earth, not onboard. A “modulator” is a subsystem that imposes information on a carrier, not the entire repeater chain. “Detector” refers to demodulation components in receivers, not satellite repeaters. Therefore, “transponders” is the correct term.

Step-by-Step Solution:

Verification / Alternative check:
Satellite specifications list the number and bandwidth of transponders (e.g., 36 MHz C-band transponders), which define the satellite’s capacity.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing Earth stations with onboard equipment; equating modulation with the entire repeat-and-forward path.

Final Answer:
transponders.