SNR for CW contact

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SNR for CW contact


I am interested in using WSPR to determine where a band might be open to make CW contacts. I find it interesting to get real-time quantitative measurements and judge where it might be feasible to work with CW (or other modes).

My understanding is that the SNR definition used in WSPR is based on a 2500 Hz bandwidth. Somewhere on these pages or in the manual it was written that the lowest acceptable SNR for a good CW op is -18 dB. Is this assuming the same 2500 Hz noise bandwidth?

So if I use a 250 Hz filter, then can I reduce this figure by 10 dB for a minimum required SNR of -28 dB? For a standard 500 Hz filter this would be about -25 dB.

What is the rule of thumb for minimum required SNR for SSB or some other digital modes such as PSK31? For these two examples, we can assume 2500 Hz noise bandwidth, that is usually how rigs are run.

Mike N9OHW