The QMX from QRP-Labs is a very compact radio that has been used with good results with FreeDV.

One thing to note is that the Digital mode is for FSK modes, such as WSPR, FT-8, or Olivia and is not the right mode for FreeDV. You need to choose USB or LSB according to normal band conventions.

The radio has audio and CAT control over USB and the ports conveniently come up named correctly.

I have found that it’s required to choose a serial rate, even though it’s a virtual serial port.

Note that if you just choose QMX the radio will switch to Digi mode on transmit. To get it to use sideband go to Tools->Options->Rig Control to force USB/LSB instead of DIGU/DIGL

By default, the QMX applies AGC and equalisation to transmitted audio so it may be good to turn these off but users have reported that this is not required.

The audio source for SSB needs to be set to USB rather than Mic. Menu > SSB > Input = SSB.

The TX Attenuation slider in FreeDV should work for the QMX. Adjusting that to -3 dB for example should cut the output power in half (i.e. 2.5W theoretical instead of 5W, actual output may vary).

For its 5W, the QMX seems to work very well running FreeDV.