public SerialPortDeviceLocationSource()

var newSrc = new SerialPortDeviceLocationSource();

//Specify the COM port the device is connected to
newSrc.ComPort = "Com3";
newSrc.BaudRate = 4800;
newSrc.AntennaHeight = 3;  // meters
                           //fill in other properties as needed

var props = new DeviceLocationProperties();
props.AccuracyThreshold = 10;   // meters

// jump to the background thread
await QueuedTask.Run(() =>
{
  //open the device
  DeviceLocationService.Instance.Open(newSrc, props);
});