The following GNU radio application adds a waterfall spectrogram to the previous CW filter program. The plot show 4 CW signals in the audio band (lower sideband) at 7023 kHz. The 700Hz signal is filtered and output to the laptop headphones by the CW bandpass filter. The frequency display is shown after the script which is as follows: #!/usr/bin/env python from gnuradio import gr from gnuradio import audio from lpf_bpf_class import Bandpass from gnuradio.qtgui import qtgui from PyQt4 import QtGui import sys, sip class cw_filter(gr.top_block): def __init__(self): gr.top_block.__init__(self) sample_rate = 44100 out_rate = 8000 kaiser = Bandpass() cw_flr = gr.fir_filter_fff(1, kaiser.bpftaps) decimate = int...