NB. When starting to use the Fldigi suite, (assuming you have already done steps 1–5 above) do the following in order:
Links:
[1] https://gblakesl.net/N1GB/N1GB_ARES.html
[2] http://gmares.org/?page_id=25
[3] https://www.jeffreykopcak.com/2015/10/19/nbemsfldigi-sound-card-calibration/
[4] http://gblakesl.net/ARES/FLDIGI-Soundcard-Calibration-Presentation.ppt