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GNU Radio Waterfall and CW Filter

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(sample_rate/out_rate)
        Bandpass.cutoff1 = 3000       
        pre_decim = Bandpass()
        dec_flr = gr.fir_filter_fff(1, pre_decim.lpftaps)
        dec = gr.keep_one_in_n(gr.sizeof_float, decimate)

        # Make a local QtApp
        self.qapp = QtGui.QApplication(sys.argv)
        fftsize = 2048

        audio_mic = audio.source(sample_rate, "plughw:0,0")
        amp1 = gr.multiply_const_ff(2.0)
        amp2 = gr.multiply_const_ff(1.0)
        dst = audio.sink (sample_rate, "")

        self.connect (audio_mic, cw_flr, amp1, dst)

        self.thr = gr.throttle(gr.sizeof_float, 100*fftsize)
        self.snk = qtgui.sink_f(fftsize, gr.firdes.WIN_BLACKMAN_hARRIS,
                         0,
                         4000,
                        "CW Kaiser BPF Filter")
                        #True, True, False, True, False)

        self.connect(audio_mic, amp2, self.thr, dec, self.snk)

        self.pyobj = sip.wrapinstance(self.snk.pyqwidget(), QtGui.QWidget)
        self.pyobj.show()

def main():
    tb = cw_filter()
    tb.start()
    tb.qapp.exec_()


if __name__ == '__main__':
    try:
        main()
    except [[KeyboardInterrupt]]:
        pass

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