Bob Motyl KK6KMU
That is your receive side. I normally set my FLDIGI waterfall receive gain to about -22 and then adjust you computer soundcard mic level to where you just see red than back off on the level a little.
I always get this messed up so here goes.
Receive level is controlled by your soundcard mic level
Transmit audio level is controlled you your soundcard speaker level.
AGC Automatic Gain Control I set to fast for digital modes AGC Protects your front end I believe. Receive side
ALC Automictic Level Control attempts to control the audio input to you transmitter. If ALC levels are too high you stand the chance to put your transmitter amplifier into the non linear region to cause noise ( harmonic noise) being transmitted.