[catliNZ]

Well in that case
Edit the tx software file Process_IDx.ino about line 187
 

Code:

// calc the current wind direction
    wind_dir = ((vane_reading - Min_vane_reading) *  360L) / (Max_vane_reading - Min_vane_reading);
    wind_dir += WDir_offs;

//addition to turn compass 180 degrees
    wind_dir += 180;
    if (wind_dir > 360)    wind_dir -= 360;
//end of addition
  
    // Precaution in case the calib values are wrong or slightly off
    if (wind_dir > 360)    wind_dir = 360;
    else if (wind_dir < 0) wind_dir = 0;
  
    wind_dir = wind_dir * 10;
    return wind_dir;
  }
#endif

#endif  // End ID2

the 180 of course can be changed to get your angle correct.
cheers, Ian