Kenwood TS-590SG Manual page 28

04 DSP
AGC loops are placed before and after the interference elimination process using the IF filter or manual notch filter, for
example. The AGC loop at the earlier stage is known as the out-band AGC, which mainly ensures that signals beyond the
reference level are not input with respect to the ADC of the input. Meanwhile, the AGC loop at the later stage operates in
the same way as conventional ones, and are referred to as in-band AGC. The target signals will stand out by operating the
in-band AGC after the bandwidth limiting or interference elimination process.
Figure 4-4 Out-band AGC Control
The basic concept of the AGC response characteristics is to control the gain of the AGC amplifier through ultra-high speed
attack in the same way as conventional models, followed by managing the gain without causing unintended fluctuations.
This helps to reduce fatigue from listening during prolonged operation.
One of the factors causing fatigue from listening is the momentary signal level overshoot due to high-speed attack. This
phenomenon is an essential characteristic to help the weak signals stand out and to minimize distortions as a receiver.
However, detection in this state results in a "clicking" sound, which may prevent the high-speed release setting from being
utilized at its fullest.
The attack sound quality is determined collectively by the characteristics including those of the AGC loop and IF filter at the
earlier and later stages respectively, as well as those of the AGC amplifier at the analog stage. The TS-590SG attempts
to resolve this issue by adopting a method that manages the gain of the out-band AGC and in-band AGC to adjust the
response characteristics of the out-band AGC dynamically and establishing the ideal attack characteristics with the two
types of AGC loops in the dual loop in-band AGC (single loop AGC in the AM mode), which possess different characteristics.
Figure 4-5 Comparison of CW Receive Waveforms between Conventional Models and TS-590SG
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