With CW, the carrier is turned on and off. WWVB transmissions involve reducing the carrier power by 17dB at the start of each second and then returning to full power 0.2 (0), 0.5 (1) or 0.8 (P) seconds later. The carrier is always on but just reduced in power which modulates the amplitude and produces a pulse-width modulated signal. Maybe the OP's signal does something like this.
Pete