High-Pitched Polytone Station (XPH)

This very strange station is a "numbers" broadcast from Russia. It translates number digits into 14 semi-musical tones, spaced 16 Hz apart. A slow callup is broadcast, then the message changes to a tone rate of 7-8 per second.

The above plot is logarithmic, taken just as the fast portion begins. The same tone is sent 10 times, not by interruption as much as by something which looks a lot like phase-shift keying, almost a PSK idler. Sync? I don't know. Also note how clipped the signal is, especially on the positive side, making it extremely rich in harmonics. This is not the recording, as the basic waveform stays the same in ionospheric fades.

The wideband, linear plot below further dramatizes these striking characteristics. We see the extremely clicky, phase-noisy keying, and harmonics out to the 15th. Awesome.