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#!/usr/bin/env python
#
# Copyright 2013 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
#
from __future__ import division
from __future__ import unicode_literals
from gnuradio import gr
from gnuradio import blocks
from gnuradio import filter
from gnuradio import analog
from gnuradio import audio
from gnuradio.filter import firdes
import sys, math
# Create a top_block
class build_graph(gr.top_block):
def __init__(self):
gr.top_block.__init__(self)
input_rate = 200e3 # rate of a broadcast FM station
audio_rate = 44.1e3 # Rate we send the signal to the speaker
# resample from the output of the demodulator to the rate of
# the audio sink.
resamp_rate = audio_rate / input_rate
# use a file as a dummy source. Replace this with a real radio
# receiver to capture signals over-the-air.
src = blocks.file_source(gr.sizeof_gr_complex, "dummy.dat", True)
# Set the demodulator using the same deviation as the receiver.
max_dev = 75e3
fm_demod_gain = input_rate / (2*math.pi*max_dev/8.0)
fm_demod = analog.quadrature_demod_cf(fm_demod_gain)
# Create a filter for the resampler and filter the audio
# signal to 15 kHz. The nfilts is the number of filters in the
# arbitrary resampler. It logically operates at a rate of
# nfilts*input_rate, so we make those adjustments when
# building the filter.
volume = 0.20
nfilts = 32
resamp_taps = firdes.low_pass_2(volume*nfilts, # gain
nfilts*input_rate, # sampling rate
15e3, # low pass cutoff freq
1e3, # width of trans. band
60, # stop band attenuaton
firdes.WIN_KAISER)
# Build the resampler and filter
resamp_filter = filter.pfb_arb_resampler_fff(resamp_rate,
resamp_taps, nfilts)
# sound card as final sink You may have to add a specific
# device name as a second argument here, something like
# "pulse" if using pulse audio or "plughw:0,0".
audio_sink = audio.sink(int(audio_rate))
# now wire it all together
self.connect(src, fm_demod)
self.connect(fm_demod, resamp_filter)
self.connect(resamp_filter, (audio_sink,0))
def main(args):
tb = build_graph()
tb.start() # fork thread and return
input('Press Enter to quit: ')
tb.stop()
if __name__ == '__main__':
main(sys.argv[1:])
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