In the K3/K3S/KX2/KX3, "RF Gain" adjusts receive path gain ahead of the AGC detector while "AF Gain" adjusts the receive path gain AFTER the AGC, if any, is applied. 73, Lyle KK7P > ... "RF Gain" in modern receivers really just sets the maximum gain > the AGC will allow, so reducing it only attenuates weaker signals.