O P T I M I Z I N G T H E A G C
A P P E N D I X C
(S6). If the preamp is turned on then that raises the input signal level into the AGC by 14dB. To keep
the Threshold at -91dBm, we therefore need to reduce the Max Gain by the same 14dB to 64dB.
To obtain the most optimal Max Gain setting it is important to know where the Threshold is in relation
to the desired input signal.
If the Threshold is placed far to the right of the desired signal's input level (Max Gain is too low)
then you may not be able to copy a weak signal. Also a suddenly appearing strong signal may
blow your ears off.
If the Threshold is placed far to the left of the desired signal's input level (Max Gain is too high)
then the desired signal will sound as loud as the noise, because you have amplified everything
up to the -13dBm level. In other words, you have destroyed your signal to noise ratio.
If the Threshold is placed at or just above the desired signal's input level you will have amplified
it to the maximum attainable without destroying the signal to noise level. A (suddenly
appearing) much stronger signal will be kept at about the same output level as that of the
desired signal and your ears will be thankful. If the desired signal is a very strong signal, the
benefit will be that its output level can be reduced, thus also reducing the noise level.
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