fix disctap if rate

op25/gr-op25_repeater/apps/multi_rx.py

@@ -135,6 +135,7 @@ class channel(object):
             self.demod = p25_demodulator.p25_demod_fb(
                          input_rate = dev.sample_rate,
                          filter_type = config['filter_type'],
+                         if_rate = config['if_rate'],
                          symbol_rate = self.symbol_rate)
         else:
             self.demod = p25_demodulator.p25_demod_cb(

op25/gr-op25_repeater/apps/p25_demodulator.py

@@ -166,6 +166,7 @@ class p25_demod_fb(p25_demod_base):
                  input_rate	= None,
                  filter_type	= None,
                  excess_bw      = _def_excess_bw,
+                 if_rate        = _def_if_rate,
                  symbol_rate	= _def_symbol_rate):
         """
 	Hierarchical block for P25 demodulation.
@@ -179,12 +180,21 @@ class p25_demod_fb(p25_demod_base):
 				gr.io_signature(1, 1, gr.sizeof_float),       # Input signature
 				gr.io_signature(1, 1, gr.sizeof_char)) # Output signature
 
-        p25_demod_base.__init__(self, if_rate=input_rate, symbol_rate=symbol_rate, filter_type=filter_type)
+        p25_demod_base.__init__(self, if_rate=if_rate, symbol_rate=symbol_rate, filter_type=filter_type)
 
         self.input_rate = input_rate
+        self.if_rate = if_rate
         self.float_sink = None
-
-        self.connect(self, self.baseband_amp, self.symbol_filter, self.fsk4_demod, self.slicer, self)
+        if input_rate != if_rate:
+            assert if_rate < input_rate
+            assert input_rate % if_rate == 0	### input rate must be multiple of if rate
+            decim = input_rate // if_rate
+            maxf = min(if_rate // 2, 6000)	### lpf cutoff at most 6 KHz
+            lpf_coeffs = filter.firdes.low_pass(1.0, input_rate, maxf, maxf//8, filter.firdes.WIN_HAMMING)
+            self.bb_decim = filter.fir_filter_fff(decim,  lpf_coeffs)
+            self.connect(self, self.bb_decim, self.baseband_amp, self.symbol_filter, self.fsk4_demod, self.slicer, self)
+        else:
+            self.connect(self, self.baseband_amp, self.symbol_filter, self.fsk4_demod, self.slicer, self)
 
     def disconnect_float(self):
         # assumes lock held or init

op25/gr-op25_repeater/apps/rx.py

@@ -215,6 +215,7 @@ class p25_rx_block (gr.top_block):
         global WIRESHARK_PORT
 
         sps = 5		# samples / symbol
+        if_rate = sps * 4800
 
         self.rx_q = gr.msg_queue(100)
         udp_port = 0
@@ -234,7 +235,7 @@ class p25_rx_block (gr.top_block):
         self.xor_cache = {}
 
         if self.baseband_input:
-            self.demod = p25_demodulator.p25_demod_fb(input_rate=capture_rate, excess_bw=self.options.excess_bw)
+            self.demod = p25_demodulator.p25_demod_fb(input_rate=capture_rate, excess_bw=self.options.excess_bw,if_rate=if_rate)
         else:	# complex input
             # local osc
             self.lo_freq = self.options.offset
@@ -244,7 +245,7 @@ class p25_rx_block (gr.top_block):
                                                        demod_type = self.options.demod_type,
                                                        relative_freq = self.lo_freq,
                                                        offset = self.options.offset,
-                                                       if_rate = sps * 4800,
+                                                       if_rate = if_rate,
                                                        gain_mu = self.options.gain_mu,
                                                        costas_alpha = self.options.costas_alpha,
                                                        excess_bw = self.options.excess_bw,
@@ -260,7 +261,7 @@ class p25_rx_block (gr.top_block):
         self.connect(source, self.demod, self.decoder)
 
         if self.baseband_input:
-            sps = int(capture_rate / 4800)
+            sps = if_rate // 4800
         plot_modes = []
         if self.options.plot_mode is not None:
             plot_modes = self.options.plot_mode.split(',')