How to save your ears when AGC is OFF (K3/K3S/KX3/KX2)

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How to save your ears when AGC is OFF (K3/K3S/KX3/KX2)

wayne burdick
Here's another feature available on all of our newer radios: the AF limiter.


AGC (automatic gain control) keeps the AF output level of a receiver relatively constant over a wide range of RF input levels. Most operators keep their receiver's AGC on at all times, so there's no need to "ride" the RF gain control.

However, some operators prefer to turn AGC off. When AGC is off, you experience the full dynamic range of received signals, which can help separate signals from each other, or just provide a more "lively" receiver sound completely free of gain adjustments. But in this case you *do* need to manually adjust RF GAIN to keep signals in a comfortable range.

The problem with this operating style is that extra-large signals can pop up unexpectedly. You might not be able to manually react fast enough to keep them in a comfortable range. This is the reason for the AF limiter.

Setting Up the AF Limiter

The AF limiter is set using CONFIG:AF LIM (K3/K3S) or MENU:AF LIM (KX3/KX2). The default value is "NOR" (normal), which puts the limit threshold very high -- around the point where the AF amplifier chain itself would cause limiting (extremely loud). So if you plan to turn AGC off, you'll need to set AF LIM lower.

A good approach is to start with AF LIM = 23. Then turn off AGC (see below), and see if you feel that the limiter needs to come on at a weaker signal level (lower number), or stronger (higher number). The manual recommends a range of 17 to 23.

Turning AGC Off

- On the K3 or K3S, hold the AGC switch (the yellow label is "OFF").

- On the KX3 or KX2, set MENU:AGC MD to OFF.

In both cases, this will change the AGC icon from "AGC-S" or "AGC-F" (AGC on, Slow or Fast) to "AGC-" (AGC off).

With AGC off, be prepared to adjust the RF GAIN control, and don't forget to adjust the AF LIM value as described above.


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