Report from Simon M0XLZ:

Using a 991a here with the NinoTNC. My settings on the radio are:

• mode: data-usb
• dial setting of 7.04575 (for GB7IOW)

On the F button:

• DT Gain 60
• Shift +200hz
• Width 500hz

On the Menu button:

• item 073 Data Out Level at 80

The received signal needs to be at least 3 S points over the noise floor.