ALC is a circuit in transmitters that governs the signal strength going into the power amplifier, preventing overloading. ALC keeps the amplifier input in the designed range for linear operation.
FT8 and splatter and the ugliness of ALC, A Sneaky Look at the Yaesu FTdx101D Transceiver, 70cm Slim Jim antenna, A 3.5MHz Receiver for SSB and CW, PSK: How to Assure a Clean Signal, Learn Morse Code by GW6ITJ, Transforming the Elecraft K3 into a SDR with K3, AUDIO590 - Audio Setup for TS-590, BPQ32 the AX25 Networking Package for Windows, Maidenhead square Calculator