This waterfall is with the following code.
if(channels == 2) { /* for my Soft66LC4 only */
for(int i =0; i < NFFT; i+=2) {
double i1 = samples[i ] + (-246.618); /* DC offset */
double q1 = samples[i+1] + (-222.262);
double i2 = i1;
double q2 = -0.32258 * i1 + 1.1443 * q1; /* gain and phase correction */
double i3 = q2; /* swap IQ */
double q3 = i2;
audio_signal[i] = i3;
audio_signal[i+1] = q3;
}
}
Note that IQ signals are swapped now, so the signals higher than the LO, which is in this case 7020kHz, appear on the right half of the display.