When this tone leaves Boulder, it's so accurate that it can be digitally counted down to 60 and used as a reference to synchronize electric generators. I don't know if this particular received signal is good enough for that, but thanks to excellent band conditions it's pretty good. The amplitude at the top shows absolutely no fading, the noise has completely quieted, and there is no wavering from ionospheric flutter. I opened up the audio bandwidth to show the yellow lines down at the bottom. One pulse is sent per second.
Short pulses are binary zeroes, longer pulses are ones.
The time ticks themselves show as transient pulses centered on 1000 Hz. Everything else is distortion. All this is down something like 20 dB, and another mix producing an 1100-Hz tone was too low to see here.