FLDIGI Users Manual 4.0
# scans: The number of scans to perform (averaging).
db Range: The dynamic range in dB (vertical scale).
Analysis tool used to evaluate Rx/Codec signal path. Can be used to measure noise floor of the codec; view the transceiver passband characteristics, Rx signal spectrum, etc.
The scope shows the results, both final and during the scan averaging. The # of scans specifies how many scans are averaged for the display. The dB range specifies the vertical scale as seen above. "Use relative dB" removes the vertical offset so that a wider range can be displayed with more detail.
Left clicking any where on the waterfall restarts the scan. You can observe the effect on the scope display. A comma separated file is also generated; ~/.fldigi/fftscan.csv which can be opened with any spread sheet program.