C
Optimizing the AGC
To gain an understanding of how to set the AGC-T or Max Gain control it is helpful to think in terms of
signal levels instead of gains. Figure 176 shows the input and output signal levels (pre and post AGC)
at various settings of the Max Gain control with the Slope set to zero.
For example (assuming the RX Gain is off) the violet line (with a Max Gain setting of 60dB) shows that
as the level of the input signal into the AGC increases from -121dBm (S1) to -73dBm (S9) the level of
the output signal out of the AGC increases from -61dBm (- 60dB) to -13dBm. For input
signal levels higher than -73dBm, the output level remains constant at -13dBm because we have set
the Slope to zero. The input signal level at which the output just reaches the maximum of -13dBm is
known as the AGC Threshold (this is different from the Hang Threshold).
If the Max Gain setting is increased, say from 60dB to 78dB (the blue line), the output signal level
reaches its maximum at a lower signal level. For a Max Gain of 78dB, the AGC Threshold is at -91 dBm
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2003-2009 FlexRadio Systems
Figure 176: Input and Output Signal Levels at Various Max Gain Settings
Appendix
C
