The YAESU FT-991A has two submodes for SSB: one for voice (USB, LSB), one for data (DataU, DataL). Main difference is the default source of signal for TX modulator. In USB, LSB it is the front mic, in Data it is the back panel connector. I use the radio with a Windows 10 computer, using default SiliconLabs driver and two virtual COM: ports. This requires the DataU setting. The VarAC program stubbornly sets my radio to USB, instead of DataU. Manual states that in Settings tab I should be able to switch these modes. I can not find any way to effect this. Is there anything I can change to get the radio being set to DataU, instead of USB?