diff --git a/src/demod/cqpsk.py b/src/demod/cqpsk.py
new file mode 100644
index 0000000..6be6ee7
--- /dev/null
+++ b/src/demod/cqpsk.py
@@ -0,0 +1,345 @@
+#
+# Copyright 2005,2006,2007 Free Software Foundation, Inc.
+#
+# cqpsk.py (C) Copyright 2009, KA1RBI
+#
+# 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 3, 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., 51 Franklin Street,
+# Boston, MA 02110-1301, USA.
+#
+
+# See gnuradio-examples/python/digital for examples
+
+"""
+differential PI/4 CQPSK modulation and demodulation.
+"""
+
+from gnuradio import gr, gru, analog, blocks, digital, filter
+from math import pi, sqrt
+import cmath
+from pprint import pprint
+
+# default values (used in __init__ and add_options)
+_def_samples_per_symbol = 10
+_def_excess_bw = 0.35
+_def_gray_code = True
+_def_verbose = False
+_def_log = False
+
+_def_costas_alpha = 0.15
+_def_gain_mu = None
+_def_mu = 0.5
+_def_omega_relative_limit = 0.005
+
+
+# /////////////////////////////////////////////////////////////////////////////
+#                           CQPSK modulator
+# /////////////////////////////////////////////////////////////////////////////
+
+class cqpsk_mod(gr.hier_block2):
+
+    def __init__(self,
+                 samples_per_symbol=_def_samples_per_symbol,
+                 excess_bw=_def_excess_bw,
+                 verbose=_def_verbose,
+                 log=_def_log):
+        """
+        Hierarchical block for RRC-filtered QPSK modulation.
+
+        The input is a byte stream (unsigned char) and the
+        output is the complex modulated signal at baseband.
+
+        @param samples_per_symbol: samples per symbol >= 2
+        @type samples_per_symbol: integer
+        @param excess_bw: Root-raised cosine filter excess bandwidth
+        @type excess_bw: float
+            @param verbose: Print information about modulator?
+            @type verbose: bool
+            @param debug: Print modualtion data to files?
+            @type debug: bool
+        """
+
+        gr.hier_block2.__init__(self, "cqpsk_mod",
+                gr.io_signature(1, 1, gr.sizeof_char),       # Input signature
+                gr.io_signature(1, 1, gr.sizeof_gr_complex)) # Output signature
+
+        self._samples_per_symbol = samples_per_symbol
+        self._excess_bw = excess_bw
+
+        if not isinstance(samples_per_symbol, int) or samples_per_symbol < 2:
+            raise TypeError, ("sbp must be an integer >= 2, is %d" % samples_per_symbol)
+
+        ntaps = 11 * samples_per_symbol
+
+        arity = 8
+
+        # turn bytes into k-bit vectors
+        self.bytes2chunks = \
+          gr.packed_to_unpacked_bb(self.bits_per_symbol(), gr.GR_MSB_FIRST)
+
+        #   0   +45 1   [+1]
+        #   1   +135    3   [+3]
+        #   2   -45 7   [-1]
+        #   3   -135    5   [-3]
+        self.pi4map = [1, 3, 7, 5]
+        self.symbol_mapper = gr.map_bb(self.pi4map)
+        self.diffenc = gr.diff_encoder_bb(arity)
+        self.chunks2symbols = gr.chunks_to_symbols_bc(psk.constellation[arity])
+
+        # pulse shaping filter
+        self.rrc_taps = filter.firdes.root_raised_cosine(
+            self._samples_per_symbol, # gain  (sps since we're interpolating by sps)
+            self._samples_per_symbol, # sampling rate
+            1.0,                      # symbol rate
+            self._excess_bw,          # excess bandwidth (roll-off factor)
+            ntaps)
+
+        self.rrc_filter = filter.interp_fir_filter_ccf(self._samples_per_symbol, self.rrc_taps)
+
+        if verbose:
+            self._print_verbage()
+
+        if log:
+            self._setup_logging()
+
+        # Connect & Initialize base class
+        self.connect(self, self.bytes2chunks, self.symbol_mapper, self.diffenc,
+                     self.chunks2symbols, self.rrc_filter, self)
+
+    def samples_per_symbol(self):
+        return self._samples_per_symbol
+
+    @staticmethod
+    def bits_per_symbol():
+        return 2
+
+    def _print_verbage(self):
+        print "\nModulator:"
+        print "bits per symbol:     %d" % self.bits_per_symbol()
+        print "Gray code:           %s" % self._gray_code
+        print "RRS roll-off factor: %f" % self._excess_bw
+
+    def _setup_logging(self):
+        print "Modulation logging turned on."
+        self.connect(self.bytes2chunks,
+                     gr.file_sink(gr.sizeof_char, "tx_bytes2chunks.dat"))
+        self.connect(self.symbol_mapper,
+                     gr.file_sink(gr.sizeof_char, "tx_graycoder.dat"))
+        self.connect(self.diffenc,
+                     gr.file_sink(gr.sizeof_char, "tx_diffenc.dat"))
+        self.connect(self.chunks2symbols,
+                     gr.file_sink(gr.sizeof_gr_complex, "tx_chunks2symbols.dat"))
+        self.connect(self.rrc_filter,
+                     gr.file_sink(gr.sizeof_gr_complex, "tx_rrc_filter.dat"))
+
+    @staticmethod
+    def add_options(parser):
+        """
+        Adds QPSK modulation-specific options to the standard parser
+        """
+        parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
+                          help="set RRC excess bandwith factor [default=%default] (PSK)")
+        parser.add_option("", "--no-gray-code", dest="gray_code",
+                          action="store_false", default=_def_gray_code,
+                          help="disable gray coding on modulated bits (PSK)")
+
+    @staticmethod
+    def extract_kwargs_from_options(options):
+        """
+        Given command line options, create dictionary suitable for passing to __init__
+        """
+        return modulation_utils.extract_kwargs_from_options(dqpsk_mod.__init__,
+                                                            ('self',), options)
+
+
+# /////////////////////////////////////////////////////////////////////////////
+#                           CQPSK demodulator
+#
+# /////////////////////////////////////////////////////////////////////////////
+
+class cqpsk_demod(gr.hier_block2):
+
+    def __init__(self,
+                 samples_per_symbol=_def_samples_per_symbol,
+                 excess_bw=_def_excess_bw,
+                 costas_alpha=_def_costas_alpha,
+                 gain_mu=_def_gain_mu,
+                 mu=_def_mu,
+                 omega_relative_limit=_def_omega_relative_limit,
+                 gray_code=_def_gray_code,
+                 verbose=_def_verbose,
+                 log=_def_log):
+        """
+        Hierarchical block for RRC-filtered CQPSK demodulation
+
+        The input is the complex modulated signal at baseband.
+        The output is a stream of floats in [ -3 / -1 / +1 / +3 ]
+
+        @param samples_per_symbol: samples per symbol >= 2
+        @type samples_per_symbol: float
+        @param excess_bw: Root-raised cosine filter excess bandwidth
+        @type excess_bw: float
+            @param costas_alpha: loop filter gain
+            @type costas_alphas: float
+            @param gain_mu: for M&M block
+            @type gain_mu: float
+            @param mu: for M&M block
+            @type mu: float
+            @param omega_relative_limit: for M&M block
+            @type omega_relative_limit: float
+            @param gray_code: Tell modulator to Gray code the bits
+            @type gray_code: bool
+            @param verbose: Print information about modulator?
+            @type verbose: bool
+            @param debug: Print modualtion data to files?
+            @type debug: bool
+        """
+
+        gr.hier_block2.__init__(self, "cqpsk_demod",
+                    gr.io_signature(1, 1, gr.sizeof_gr_complex), # Input signature
+                    gr.io_signature(1, 1, gr.sizeof_float))       # Output signature
+
+        self._samples_per_symbol = samples_per_symbol
+        self._excess_bw = excess_bw
+        self._costas_alpha = costas_alpha
+        self._mm_gain_mu = gain_mu
+        self._mm_mu = mu
+        self._mm_omega_relative_limit = omega_relative_limit
+        self._gray_code = gray_code
+
+        if samples_per_symbol < 2:
+            raise TypeError, "sbp must be >= 2, is %d" % samples_per_symbol
+
+        arity = pow(2,self.bits_per_symbol())
+
+        # Automatic gain control
+        scale = (1.0/16384.0)
+        self.pre_scaler = blocks.multiply_const_cc(scale)   # scale the signal from full-range to +-1
+        #self.agc = analog.agc2_cc(0.6e-1, 1e-3, 1, 1, 100)
+        self.agc = analog.feedforward_agc_cc(16, 2.0)
+
+        # RRC data filter
+        ntaps = 11 * samples_per_symbol
+        self.rrc_taps = filter.firdes.root_raised_cosine(
+            1.0,                      # gain
+            self._samples_per_symbol, # sampling rate
+            1.0,                      # symbol rate
+            self._excess_bw,          # excess bandwidth (roll-off factor)
+            ntaps)
+        self.rrc_filter=filter.interp_fir_filter_ccf(1, self.rrc_taps)
+
+        if not self._mm_gain_mu:
+            sbs_to_mm = {2: 0.050, 3: 0.075, 4: 0.11, 5: 0.125, 6: 0.15, 7: 0.15}
+            self._mm_gain_mu = sbs_to_mm[samples_per_symbol]
+
+        self._mm_omega = self._samples_per_symbol
+        self._mm_gain_omega = .25 * self._mm_gain_mu * self._mm_gain_mu
+        self._costas_beta  = 0.25 * self._costas_alpha * self._costas_alpha
+        fmin = -0.025
+        fmax = 0.025
+
+        self.receiver=digital.mpsk_receiver_cc(
+            arity, pi/4.0,
+            2*pi/150,
+            fmin, fmax,
+            self._mm_mu, self._mm_gain_mu,
+            self._mm_omega, self._mm_gain_omega,
+            self._mm_omega_relative_limit
+        )
+
+        self.receiver.set_alpha(self._costas_alpha)
+        self.receiver.set_beta(self._costas_beta)
+
+        # Perform Differential decoding on the constellation
+        self.diffdec = digital.diff_phasor_cc()
+
+        # take angle of the difference (in radians)
+        self.to_float = blocks.complex_to_arg()
+
+        # convert from radians such that signal is in -3/-1/+1/+3
+        self.rescale = blocks.multiply_const_ff( 1 / (pi / 4) )
+
+        if verbose:
+            self._print_verbage()
+
+        if log:
+            self._setup_logging()
+
+        # Connect & Initialize base class
+        self.connect(self, self.pre_scaler, self.agc, self.rrc_filter, self.receiver,
+                     self.diffdec, self.to_float, self.rescale, self)
+
+    def samples_per_symbol(self):
+        return self._samples_per_symbol
+
+    @staticmethod
+    def bits_per_symbol():
+        return 2
+
+    def _print_verbage(self):
+        print "\nDemodulator:"
+        print "bits per symbol:     %d"   % self.bits_per_symbol()
+        print "Gray code:           %s"   % self._gray_code
+        print "RRC roll-off factor: %.2f" % self._excess_bw
+        print "Costas Loop alpha:   %.2e" % self._costas_alpha
+        print "Costas Loop beta:    %.2e" % self._costas_beta
+        print "M&M mu:              %.2f" % self._mm_mu
+        print "M&M mu gain:         %.2e" % self._mm_gain_mu
+        print "M&M omega:           %.2f" % self._mm_omega
+        print "M&M omega gain:      %.2e" % self._mm_gain_omega
+        print "M&M omega limit:     %.2f" % self._mm_omega_relative_limit
+
+    def _setup_logging(self):
+        print "Modulation logging turned on."
+        self.connect(self.pre_scaler,
+                     gr.file_sink(gr.sizeof_gr_complex, "rx_prescaler.dat"))
+        self.connect(self.agc,
+                     gr.file_sink(gr.sizeof_gr_complex, "rx_agc.dat"))
+        self.connect(self.rrc_filter,
+                     gr.file_sink(gr.sizeof_gr_complex, "rx_rrc_filter.dat"))
+        self.connect(self.receiver,
+                     gr.file_sink(gr.sizeof_gr_complex, "rx_receiver.dat"))
+        self.connect(self.diffdec,
+                     gr.file_sink(gr.sizeof_gr_complex, "rx_diffdec.dat"))
+        self.connect(self.to_float,
+                     gr.file_sink(gr.sizeof_float, "rx_to_float.dat"))
+        self.connect(self.rescale,
+                     gr.file_sink(gr.sizeof_float, "rx_rescale.dat"))
+
+    @staticmethod
+    def add_options(parser):
+        """
+        Adds modulation-specific options to the standard parser
+        """
+        parser.add_option("", "--excess-bw", type="float", default=_def_excess_bw,
+                          help="set RRC excess bandwith factor [default=%default] (PSK)")
+        parser.add_option("", "--no-gray-code", dest="gray_code",
+                          action="store_false", default=_def_gray_code,
+                          help="disable gray coding on modulated bits (PSK)")
+        parser.add_option("", "--costas-alpha", type="float", default=_def_costas_alpha,
+                          help="set Costas loop alpha value [default=%default] (PSK)")
+        parser.add_option("", "--gain-mu", type="float", default=_def_gain_mu,
+                          help="set M&M symbol sync loop gain mu value [default=%default] (PSK)")
+        parser.add_option("", "--mu", type="float", default=_def_mu,
+                          help="set M&M symbol sync loop mu value [default=%default] (PSK)")
+
+    @staticmethod
+    def extract_kwargs_from_options(options):
+        """
+        Given command line options, create dictionary suitable for passing to __init__
+        """
+        return modulation_utils.extract_kwargs_from_options(
+            cqpsk_demod.__init__, ('self',), options)
diff --git a/src/demod/osmosdr-tetra_demod_fft.py b/src/demod/osmosdr-tetra_demod_fft.py
new file mode 100755
index 0000000..81fbe9d
--- /dev/null
+++ b/src/demod/osmosdr-tetra_demod_fft.py
@@ -0,0 +1,255 @@
+#!/usr/bin/env python
+
+# Copyright 2012 Dimitri Stolnikov <horiz0n@gmx.net>
+
+# Usage:
+# src$ ./demod/python/osmosdr-tetra_demod_fft.py -o /dev/stdout | ./float_to_bits /dev/stdin /dev/stdout | ./tetra-rx /dev/stdin
+#
+# Adjust the center frequency (-f) and gain (-g) according to your needs.
+# Use left click in Wideband Spectrum window to roughly select a TETRA carrier.
+# In Wideband Spectrum you can also tune by 1/4 of the bandwidth by clicking on the rightmost/leftmost spectrum side.
+# Use left click in Channel Spectrum windows to fine tune the carrier by clicking on the left or right side of the spectrum.
+
+
+import sys
+import math
+from gnuradio import gr, gru, eng_notation, blocks, filter
+from gnuradio.filter import pfb
+from gnuradio.eng_option import eng_option
+from gnuradio.wxgui import fftsink2, scopesink2, forms, TRIG_MODE_AUTO
+from grc_gnuradio import wxgui as grc_wxgui
+from optparse import OptionParser
+import osmosdr
+import wx
+
+try:
+    import cqpsk
+except:
+    from tetra_demod import cqpsk
+
+# applies frequency translation, resampling and demodulation
+
+class top_block(grc_wxgui.top_block_gui):
+  def __init__(self):
+    grc_wxgui.top_block_gui.__init__(self, title="Top Block")
+
+    options = get_options()
+
+    self.ifreq = options.frequency
+    self.rfgain = options.gain
+
+    self.src = osmosdr.source(options.args)
+    self.src.set_center_freq(self.ifreq)
+    self.src.set_sample_rate(int(options.sample_rate))
+
+    if self.rfgain is None:
+        self.src.set_gain_mode(1)
+        self.iagc = 1
+        self.rfgain = 0
+    else:
+        self.iagc = 0
+        self.src.set_gain_mode(0)
+        self.src.set_gain(self.rfgain)
+
+    # may differ from the requested rate
+    sample_rate = self.src.get_sample_rate()
+    sys.stderr.write("sample rate: %d\n" % (sample_rate))
+
+    symbol_rate = 18000
+    sps = 2 # output rate will be 36,000
+    out_sample_rate = symbol_rate * sps
+
+    options.low_pass = options.low_pass / 2.0
+
+    if sample_rate == 96000: # FunCube Dongle
+        first_decim = 2
+    else:
+        first_decim = 10
+
+    self.offset = 0
+
+    taps = filter.firdes.low_pass(1.0, sample_rate, options.low_pass, options.low_pass * 0.2, filter.firdes.WIN_HANN)
+    self.tuner = filter.freq_xlating_fir_filter_ccf(first_decim, taps, self.offset, sample_rate)
+
+    self.demod = cqpsk.cqpsk_demod(
+        samples_per_symbol = sps,
+        excess_bw=0.35,
+        costas_alpha=0.03,
+        gain_mu=0.05,
+        mu=0.05,
+        omega_relative_limit=0.05,
+        log=options.log,
+        verbose=options.verbose)
+
+    self.output = blocks.file_sink(gr.sizeof_float, options.output_file)
+
+    rerate = float(sample_rate / float(first_decim)) / float(out_sample_rate)
+    sys.stderr.write("resampling factor: %f\n" % rerate)
+
+    if rerate.is_integer():
+        sys.stderr.write("using pfb decimator\n")
+        self.resamp = pfb.decimator_ccf(int(rerate))
+    else:
+        sys.stderr.write("using pfb resampler\n")
+        self.resamp = pfb.arb_resampler_ccf(1 / rerate)
+
+    self.connect(self.src, self.tuner, self.resamp, self.demod, self.output)
+
+    self.Main = wx.Notebook(self.GetWin(), style=wx.NB_TOP)
+    self.Main.AddPage(grc_wxgui.Panel(self.Main), "Wideband Spectrum")
+    self.Main.AddPage(grc_wxgui.Panel(self.Main), "Channel Spectrum")
+    self.Main.AddPage(grc_wxgui.Panel(self.Main), "Soft Bits")
+
+    def set_ifreq(ifreq):
+        self.ifreq = ifreq
+        self._ifreq_text_box.set_value(self.ifreq)
+        self.src.set_center_freq(self.ifreq)
+
+    self._ifreq_text_box = forms.text_box(
+        parent=self.GetWin(),
+        value=self.ifreq,
+        callback=set_ifreq,
+        label="Center Frequency",
+        converter=forms.float_converter(),
+    )
+    self.Add(self._ifreq_text_box)
+
+    def set_iagc(iagc):
+        self.iagc = iagc
+        self._agc_check_box.set_value(self.iagc)
+        self.src.set_gain_mode(self.iagc, 0)
+        self.src.set_gain(0 if self.iagc == 1 else self.rfgain, 0)
+
+    self._agc_check_box = forms.check_box(
+        parent=self.GetWin(),
+        value=self.iagc,
+        callback=set_iagc,
+        label="Automatic Gain",
+        true=1,
+        false=0,
+    )
+
+    self.Add(self._agc_check_box)
+
+    def set_rfgain(rfgain):
+        self.rfgain = rfgain
+        self._rfgain_slider.set_value(self.rfgain)
+        self._rfgain_text_box.set_value(self.rfgain)
+        self.src.set_gain(0 if self.iagc == 1 else self.rfgain, 0)
+
+    _rfgain_sizer = wx.BoxSizer(wx.VERTICAL)
+    self._rfgain_text_box = forms.text_box(
+        parent=self.GetWin(),
+        sizer=_rfgain_sizer,
+        value=self.rfgain,
+        callback=set_rfgain,
+        label="RF Gain",
+        converter=forms.float_converter(),
+        proportion=0,
+    )
+    self._rfgain_slider = forms.slider(
+        parent=self.GetWin(),
+        sizer=_rfgain_sizer,
+        value=self.rfgain,
+        callback=set_rfgain,
+        minimum=0,
+        maximum=50,
+        num_steps=200,
+        style=wx.SL_HORIZONTAL,
+        cast=float,
+        proportion=1,
+    )
+
+    self.Add(_rfgain_sizer)
+
+    self.Add(self.Main)
+
+    def fftsink2_callback(x, y):
+        if abs(x / (sample_rate / 2)) > 0.9:
+            set_ifreq(self.ifreq + x / 2)
+        else:
+            sys.stderr.write("coarse tuned to: %d Hz\n" % x)
+            self.offset = x
+            self.tuner.set_center_freq(self.offset)
+
+    self.scope = fftsink2.fft_sink_c(self.Main.GetPage(0).GetWin(),
+        title="Wideband Spectrum (click to coarse tune)",
+        fft_size=1024,
+        sample_rate=sample_rate,
+        ref_scale=2.0,
+        ref_level=0,
+        y_divs=10,
+        fft_rate=10,
+        average=False,
+        avg_alpha=0.6)
+
+    self.Main.GetPage(0).Add(self.scope.win)
+    self.scope.set_callback(fftsink2_callback)
+
+    self.connect(self.src, self.scope)
+
+    def fftsink2_callback2(x, y):
+        self.offset = self.offset - (x / 10)
+        sys.stderr.write("fine tuned to: %d Hz\n" % self.offset)
+        self.tuner.set_center_freq(self.offset)
+
+    self.scope2 = fftsink2.fft_sink_c(self.Main.GetPage(1).GetWin(),
+        title="Channel Spectrum (click to fine tune)",
+        fft_size=1024,
+        sample_rate=out_sample_rate,
+        ref_scale=2.0,
+        ref_level=-20,
+        y_divs=10,
+        fft_rate=10,
+        average=False,
+        avg_alpha=0.6)
+
+    self.Main.GetPage(1).Add(self.scope2.win)
+    self.scope2.set_callback(fftsink2_callback2)
+
+    self.connect(self.resamp, self.scope2)
+
+    self.scope3 = scopesink2.scope_sink_f(
+        self.Main.GetPage(2).GetWin(),
+        title="Soft Bits",
+        sample_rate=out_sample_rate,
+        v_scale=0,
+        v_offset=0,
+        t_scale=0.001,
+        ac_couple=False,
+        xy_mode=False,
+        num_inputs=1,
+        trig_mode=TRIG_MODE_AUTO,
+        y_axis_label="Counts",
+    )
+    self.Main.GetPage(2).Add(self.scope3.win)
+
+    self.connect(self.demod, self.scope3)
+
+def get_options():
+    parser = OptionParser(option_class=eng_option)
+
+    parser.add_option("-a", "--args", type="string", default="",
+        help="gr-osmosdr device arguments")
+    parser.add_option("-s", "--sample-rate", type="eng_float", default=1800000,
+        help="set receiver sample rate (default 1800000)")
+    parser.add_option("-f", "--frequency", type="eng_float", default=394.4e6,
+        help="set receiver center frequency")
+    parser.add_option("-g", "--gain", type="eng_float", default=None,
+        help="set receiver gain")
+
+    # demodulator related settings
+    parser.add_option("-l", "--log", action="store_true", default=False, help="dump debug .dat files")
+    parser.add_option("-L", "--low-pass", type="eng_float", default=25e3, help="low pass cut-off", metavar="Hz")
+    parser.add_option("-o", "--output-file", type="string", default="out.float", help="specify the bit output file")
+    parser.add_option("-v", "--verbose", action="store_true", default=False, help="dump demodulation data")
+    (options, args) = parser.parse_args()
+    if len(args) != 0:
+        parser.print_help()
+        raise SystemExit, 1
+
+    return (options)
+
+if __name__ == '__main__':
+        tb = top_block()
+        tb.Run(True)