Wes and Ed,
It's important to realize that in the K3 and later Elecraft rigs, all of
this is happening in the digital domain. One thing we learned about DSP
in pro audio is that dynamics processing burns a LOT processor cycles.
DSP SIMULATES the behavior of analog circuitry, but depending on the
code and the processor, the quality of the emulation can be varying
degrees of ideal.
ALSO -- those of us who have worked in broadcast audio know that
dynamics processing can be a VERY complex business, especially when
you're trying to do a lot of it, and even with a budget far larger than
in a ham rig. Even in analog, it's tricky to do a LOT of gain change and
still sound good. A handful of designers were good at it, and made a lot
of money for themselves, or their employer, or both.
And I'll repeat my previous observation that a signal path with gain
that varies with time or with the signal amplitude is NOT a linear
device, and non-linearity => distortion.
73, Jim K9YC
On Tue,3/7/2017 1:53 PM, Wes Stewart wrote:
AGC adjusts the receiver gain, compared to the audio bits, rather
slowly and DOES NOT change the "dynamic range."
If you're listening to a signal and it's too loud for your ears and
you turn the audio gain down 10 dB, does that change the amplitude
ratio of any signal you're listening to? No, it lowers everything by
10 dB. AGC is no different, it just operates at another location in
the radio.
IMHO, this thinking is the result of looking at too many ACG slope,
threshold, and phase of the moon charts and assuming that bigger
signals have their gain reduced more that smaller ones at the same
instant in time.
Wes N7WS
On 3/7/2017 2:19 PM, Ed Muns wrote:
Decoders operate on the audio stream presented to them from the
receiver.
The decoding algorithms use the difference in audio level at each
instant in
time to make bit decisions. AGC reduces those differences and thus
increases the bit error rate.
Of course, it is important to adjust the absolute audio levels so
that the
dynamic range of the signal(s) is placed within the dynamic range of the
decoder. But, compressing the dynamic range, i.e., AGC, increases
the error
rate of the decoder.
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