FFTDSP in Time Integration Mode  

The FFTDSP Integration mode allows signal detection well below the noise level.  The above screen shows a three hour period of the WWV 15 Mhz signal with "integration" mode set to 99.  At this setting, a carrier can be detected 10 dB below the noise.  During this period, the receiver was in SSB mode with an offset of 1 Khz.