FM Modulation

#!/usr/bin/env python
#
# Copyright 2004 Free Software Foundation, Inc.
# 
# This file is part of GNU Radio
# 
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
# 
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
# Boston, MA 02111-1307, USA.
# 

from gnuradio import gr
from gnuradio import audio
import sys
import math

def build_graph ():
	sampling_freq = 8e6

	fg = gr.flow_graph ()

        audio_src = gr.sig_source_f (sampling_freq, gr.GR_SIN_WAVE, 1e3, 1, 0)
	rf_src = gr.sig_source_c (sampling_freq, gr.GR_SIN_WAVE, 255e3, 1, 0)

	fm_mod = gr.frequency_modulator_fc(.5)
	mixer = gr.multiply_cc ()

	dst = gr.file_sink (gr.sizeof_gr_complex, "fm_out")

	fg.connect (audio_src, fm_mod)
	fg.connect (fm_mod, (mixer, 0) )
	fg.connect (rf_src, (mixer, 1) )
	fg.connect (mixer, dst)

	return fg

def main ():
	fg = build_graph()
	fg.start()
	raw_input ('Press Enter to quit')
	fg.stop()

if __name__ == '__main__':
	main ()