>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

Hi John,

The vertical axis is audio frequency. Basically it is waterfall as in FT8, but turned 90 degrees. What you see is a carrier frequency you are receiving. If you change frequency to an FT8 frequency you should see multiple horizontal lines. on a busy band.

73, Reino OH3mA