Locked Fast Graph waterfall presentation #MSK144


I am puzzled by the waterfall display in MSK144.  A line is displayed that seemingly indicates a signal of constant amplitude.  When conditions are quiet I can hear an audio beat note that changes as my receiver frequency is slowly changed.

What puzzles me is that as I vary the frequency of the receiver the line displayed by the waterfall moves up and down.  If the horizontal axis of the display is time and the vertical axis is signal amplitude, the indication is that the audio response of my receiver is not at all flat.  However, the receiver response is set to be over 3 KHz and the audio amplitude from the speaker sounds pretty flat.

What am I missing?

John,  W0GN

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