glfer is a GTK+ application that shows the input
signal frequency spectrum in a waterfall display
and can also control a transmitter to emit slow-CW
(QRSS) signals. The signal to be analyzed can be
acquired in real-time from the sound card or can
be read from a WAV file. The signal spectrum can
be computed using four different spectral
estimators. The spectrogram display can be saved
as an image; you can choose to save the entire
window, or select a rectangular region to save
with the mouse.