Also known as: AFC, automatic frequency control

Automatic frequency control (AFC) continuously measures a residual carrier-frequency offset and nudges the receiver to cancel it, keeping the demodulator centred on the signal as oscillators drift.¹ Where PPM correction fixes a static error, AFC tracks a changing one.

AFC continuously corrects carrier-frequency offset, keeping the demodulator locked as the signal drifts.

Overview

AFC often works alongside a Costas loop (for phase) and appears in GopherTrunk’s receiver telemetry as a carrier-error reading; a steadily rotating constellation is the symptom AFC is there to remove.

Sources

1. Automatic frequency control — Wikipedia, on tracking and cancelling carrier-frequency offset. ↩

See also

• PPM frequency correction
• Costas loop
• Demodulation
• Constellation diagram

Learn it step by step

• Tuning for a clean lock