Hi, I am currently trying to implement a modulator/demodulator for TETRA using pi/4 DQPSK. I tried to use cqpsk.py which was provided with this package, but apparently some functions such as psk.constellation[] are not available in the new version of gnuradio. I created a list of constellation points to be used by chunks_to_symbols_bc() function, and I think this has solved this issue. I have another issue: when I modulate a string of bits in a file, and then demodulate it, the output contains 10 zeros and then a few numbers between 0 to 255 which does not seem to be related to the input bit stream at all. Could anyone please advise me on the matter? I am using GNURadio3.6.0, and main bits of code are attached: Regards,   Vahid CQPSK.py cqpsk_mod() modification: ... self.pi4map = [1, 3, 7, 5]     self.constel = [1+0j,0.7+0.7j,0+1j,-0.7+07j,-1+0j,-0.7-0.7j,0-1j,0.7-0.7j]         self.symbol_mapper = gr.map_bb(self.pi4map)         self.diffenc = gr.diff_encoder_bb(arity)         self.chunks2symbols = gr.chunks_to_symbols_bc(self.constel) ... ------------------------------------------------------------------- Modulator:         sample_rate = options.sample_rate         symbol_rate = 18000         sps = 2            IN = gr.file_source(gr.sizeof_char, options.input_file, repeat = False)     #IN = (1,0,0,0,1,1,0,0)     #src = gr.vector_source_b (IN)         MOD = cqpsk.cqpsk_mod( samples_per_symbol = sps,                                  excess_bw=0.35,                 log=options.log,                                                              verbose=options.verbose)         OUT = gr.file_sink(gr.sizeof_gr_complex, options.output_file) #        r = float(sample_rate) / float(new_sample_rate) #        INTERPOLATOR = gr.fractional_interpolator_cc(0, r)         self.connect(IN, MOD, OUT) --------------------------------------------------------------- Demodulator:         sample_rate = options.sample_rate         symbol_rate = 18000         sps = 2         # output rate will be 36,000         ntaps = 11 * sps         new_sample_rate = symbol_rate * sps         channel_taps = gr.firdes.low_pass(1.0, sample_rate, options.low_pass, options.low_pass * 0.1, gr.firdes.WIN_HANN)         FILTER = gr.freq_xlating_fir_filter_ccf(1, channel_taps, options.calibration, sample_rate)         sys.stderr.write("sample rate: %d\n" %(sample_rate))         IN = gr.file_source(gr.sizeof_gr_complex, options.input_file, repeat = False)         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.convert = gr.float_to_char()     self.convert2 = gr.float_to_char()                    OUT = gr.file_sink(gr.sizeof_char, options.output_file)     self.sink1 = gr.vector_sink_b()         r = float(sample_rate) / float(new_sample_rate)         INTERPOLATOR = gr.fractional_interpolator_cc(0, r)         self.connect(IN, FILTER, INTERPOLATOR, DEMOD, self.convert, OUT)     self.connect (DEMOD,self.convert2,self.sink1)     def print_data(self):     print "data in sink1 is: ",self.sink1.data() ---------------