What control is typically adjusted for proper ALC setting on a single sideband transceiver?
Why ALC (automatic level control) monitors the transmitter's drive level and pulls back gain when the audio drives the final stage beyond its linear range. Since the audio chain is what sets that drive, you set ALC action by adjusting the microphone or transmit audio gain until the ALC meter just barely flicks into its indicated range on voice peaks. Too much gain produces flat-topping, splatter into adjacent frequencies, and distorted audio, while too little gives weak talk power.
Watch out RF clipping or speech processing changes the average-to-peak ratio of the audio for more punch, but it is a separate control from the gain that sets ALC; the attenuator only affects the receiver front end, and antenna tuning controls match impedance, not drive level.
ALC watches your voice: turn the mic gain up only until ALC just tickles, no more.