Spectrum Replay Function

The Spectrum "Replay" Function (in Spectrum Lab)

The 'spectrum replay' function converts data from SL's spectrum buffer back into "audio" so you can hear it in the speaker.

More technically, it uses an inverse FFT to transform chunks of data from the frequency domain back into the time domain.

This only works if ...

the data in the spectrum buffer are complex FFTs (because we need amplitude and phase to restore the original signals),
the FFT windowing function must be one of the "raised-cosine"-like types (preferably the "Hann"-window)
there must be an overlap of exactly 50 percent between two consecutive FFTs.
(which means, the option "automatic scroll interval" must be set in the display settings).

The program will check if the settings of the main spectrum analyser are "ok" for this function, and automatically adjust them if necessary.

To activate the spectrum playback function, first let the spectrum analyser run in "waterfall" mode for some time (until the buffer contains enough data). Then, on the waterfall display, select the region of interest with the mouse:

move the mouse pointer to the upper left corner of the area you want to replay;
press and hold the left mouse button;
move the mouse pointer to the lower right corner. A red frame will mark the selected area on the screen.
Finally, release the mouse button. A popup menu like this will appear :

In that menu, select "Replay from Spectrum Buffer" to open this control panel:

<ToDo>: A lot.. describe the controls on the Spectrum Replay Panel ...