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Jay,
one more remark on the interpretation of your
observation: In your image, there is clearly
a 1.66 Hz envelope structure. Given the 11.905 kHz sequence [ N . K E . . ], this must be a
superposition of K (Krasnodar, presumably across the Atlantic)
and E (Khabarovsk, more likely across
the Pacific). Apparently the Krasnodar signal is experiencing a phase
advance during the observation period, caused by sunrise over Europe and
the Atlantic lowering the D-layer.
73, Markus
The
mechanism is similar to selective fading, but the delay
involved is not from propagation but from the (much longer) transmitter
delay. If you were for example getting only N and K, the two dashes 1.2
seconds apart would result in a 0.83 Hz periodic ripple in the spectral
envelope.
As the transmitters are laid out on a ~ 6000 km
baseline, the components will have different diurnal phase variations,
resulting in a slow movement of the minima in the spectrogram. If the
later component is lagging more, the ripple pattern moves down in frequency
(ie. contracts towards zero).
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