[arm-allstar] Telemetry Volume -- TX DSP level

[David McGough]

The TX DSP level is a high-precision software level adjustment. The 
default setting is 999, which means no change in level at the software 
layer.

Simpleusb-tune-menu options 3 and 4 adjust the hardware mixer volume level 
in the CM1xy chip itself. The original CM108 chips had 152 mixer steps 
from no output to max.  Some newer chips have very few mixer level 
steps---less than 40!  This may be too course to get the level fine-tuned, 
hence why the TX DSP level feature got added.

The best adjustment approach is to first leave TX DSP set to 999 and try 
adjusting options 3 and/or 4 to get the level optimal. If you reach a 
point where can't get the perfect "sweet spot" with options 3/4, the best 
plan is to set the 3/4 level slightly high and then adjust TX DSP down 
from 999 to reach the exact setting needed.


73, David KB4FXC



This setting was fairly recently added to fine-tune levels where the hardware 

On Wed, 16 Dec 2020, "Rob Seaman via ARM-allstar" wrote:

> I've had this distortion issue as well and found in the 
> simpleusb-tune-menu, changing option 7 (Set Transmit DSP Level) from 999 
> down to something around 700 or 800 fixed it.
> 
> Cheers,
> 
> Rob...
> VK6LD
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