The IC-7700 and IC-7800 have two AG

The IC-7700 and IC-7800 have two AGC loops, which we will term primary and secondary. (See Fig.2.) The primary AGC loop derives its AGC voltage within the DSP unit, at the input of the gain-controlled amplifier preceding the BPF (IF filter process). It adjusts the input level to the BPF, and also feeds a dedicated DAC which drives the analogue AGC line controlling the gain of the receiver's 1st IF amplifier following the 1st IF roofing filter. This AGC loop prevents strong signals outside the BPF passband from saturating the 1st IF amplifier and 2nd mixer, and improves the dynamic range in regard to adjacent signals.Here is a concise description of the IC-7800's AGC subsystem.The secondary AGC loop derives its AGC voltage at the digital IF filter (BPF) output which has only passed the desired signal, thus exploiting the digital IF filter to the full. As the primary AGC loop will already have adjusted the gain distribution in the analogue RF/IF chain preceding the ADC, there is a high degree of confidence that only the desired signal will enter the secondary AGC loop. This loop will maintain the digital signal level at the DAC input within the optimum range for decoding.In addition to the menu-configurable AGC time constants (slow, medium and fast), the manual AGC control offers fine adjustment of AGC hang/decay time.