Using AO40rcv as an audio analyser
AO40rcv is a program written by AE4JY commonly used for telemetry decoding from AO40. It is also quite a useful audio spectrum analyser and waterfall display, and can be used to measure audio signal to noise ratio and to display weak signals.
The program has been tested with G3RUH's audio test signals, as shown in the following screen captures (click each to enlarge)
10dB 20dB 30dB 40dB
It can be seen from these captures that:
1. The scale of the spectrum analyser display is approximately 10dB/div
2. The apparent S/N on the display is 10dB lower than G3RUH's quoted signal to noise ratios. His numbers are specified as S/N in 1Hz bandwidth, so AO40rcv seems to have an effective bandwidth of ~10Hz. Most stations receiving signals from space probes are quoting S/N ratios in 1Hz bandwidth, so 10dB needs to be added to numbers measured off AO40rcv.
3. AO40RCV's waterfall can detect signals down to approximately 10dB S/N in 1Hz bandwidth.