How this works: wsprd reports SNR normalised to a 2500 Hz reference bandwidth — this is the real channel SNR, not a coding-adjusted figure. WSPR's remarkable sensitivity (decoding at −29 dB SNR) comes from its coding gain, but the reported SNR value is the actual signal-to-noise ratio on the channel in that 2500 Hz window (see PA3FWM's analysis of amateur mode SNRs).

To predict the SNR your SSB transmitter would produce on the same path, two corrections are applied:
1. Power scaling: the path loss is constant, so SNR scales linearly with TX power — power_gain = your_power_dBm − wspr_tx_dBm.
2. Bandwidth penalty: SSB occupies ~2700 Hz; the wsprd reference is 2500 Hz. A wider noise bandwidth admits more noise, reducing SNR by 10 × log₁₀(2700 ÷ 2500) ≈ −0.33 dB.

Predicted SSB SNR (in 2700 Hz BW) = mean WSPR SNR + power_gain − 0.33 dB

The mean WSPR SNR and mean TX power are averaged across all spots for a country/band, making the prediction robust against outliers. Signal quality thresholds follow the amateur RS report system: Excellent ≥ +15 dB (RS 5), Good ≥ +10 dB (RS 4), Workable ≥ +6 dB (RS 3), Marginal ≥ +3 dB (RS 2), Very Poor ≥ 0 dB (RS 1), Not Viable < 0 dB. Assumes reciprocal propagation and does not account for antenna gain differences.