Ron
The advantage that SSB and CW have over other modes accrues as a result of the detection bandwidth used and much less the result of the modulation method. AM is typically detected in a 5-10 kHz bandwidth, SSB in a 2.4 - 3 kHz BW, and CW in a 100 - 400 Hz BW. The advantage each of those modes has is inversely proportional to the detection bandwidth. The exception to that rule is AM where a significant amount of the power is "thrown away" in the carrier and does not contribute to the modulation.
Digital modes like WSPR and FT8 use the SSB bandwidth for reception but then use a much more narrow bandwidth for detection inside the computer software. So the reception bandwidth is whatever your receiver uses for a filter, typically in the 2.4 - 3.0 kHz range. But the detection bandwidth for FT8 is only 50 Hz and for WSPR about 6 Hz. When you get reception reports on these modes showing a negative signal to noise ratio, -17 dB for example, that number is generated by comparing the received signal level to the full bandwidth noise of SSB. Reception at negative signal to noise levels is nonsense but this number is easy to generate and makes for eye-popping stats.
Probably a lot more than you ever wanted to know....... sometimes I can't stop myself.
WA8TOD
