[arm-allstar] Linear vs. Log audio plots

[Doug Crompton]

​Dave did some plotting of the TX audio level changes using the linear and
log methods. As expected they are quite different. The linear has better
spread in the high and low extremes and the log in the center. I might
point out that many of us are using the newer URI which by default would
use the log method and would have little adjustment at the ends of the
1-999 range. The linear may be preferred but since this hack has been in
the code for so long we are leaving it in as default but giving you the
ability to select linear or log manually. ​Here are his comments and graphs
.

Here are GNUplot graphs showing the linear and log modes of TX audio level
adjustment. The log mode seems whacky to me, but, I verified that is the
correct formula used in the channel driver!

NOTE that the CM1xy mixer range is 0 to 152.

Linear calculation (old URI cards and tx_audio_level_method == 1):

https://hamvoip.org/photos/Gnuplot-TX-method-1-linear.png


Log calculation (any non-cm108 adapter):

https://hamvoip.org/photos/Gnuplot-TX-method-2-log.png

73, David KB4FXC