14 Jan 2015
Comparisons were recently posted on the RSGB LF reflector. I am sorry but I cannot recall the author, although I think it was by a Dutch station. Basically it showed (using 2500Hz bandwidth) that WSPR2 (2 minute WSPR) is some 29dB better than SSB and 12wpm CW some 15dB better than SSB. Of course there are all sorts of provisos and caveats, but it goes to show why WSPR is so very good with very weak signals although only basic data is usually exchanged with WSPR.