Software Defined Radio - how does it work? Part 8
Hi Habr.
In a previous article about Software Defined Radio, a question was asked how to decode RDS using GNU Radio. The RDS decoder is not so simple to create from scratch, but fortunately for us, it is already built into GNU Radio, so it’s easy to see how it works without writing a single line of code, just RTL-SDR receiver.
')
How it works, continued under the cut.
About GNU Radio and its installation, I will not repeat, it has already been described earlier . In short, the distribution under Windows can be found here . Let's go over to the RDS itself.
If someone suddenly does not know, RDS (Radio Data System) is a protocol used in ordinary FM broadcasting to transmit additional digital information (time, exchange rates, weather, etc.). The transmission goes at a speed of 1187.5bps at a frequency of 57KHz (3rd harmonic of the pilot tone), to minimize the frequency band, BPSK (Binary Phase Shift Keying) phase coding is used. The RDS bit level has already been considered in the Habré earlier , well, we move on to GNU Radio.
The decoder for GNU Radio was made about 10 years ago , but that version is already useless to watch, the names of many units have changed, and the examples cited there no longer work. Updated fork can be taken from here .
By the way, it didn’t work to compile gr-rds from source files for Windows - cmake produces errors for the absence of Boost, although it is installed. It is not clear by the way why over the years of cmake and boost, cmake has not been taught to find ways in Windows - like finding a folder on the disk is not a rocket science at all (if anyone knows the solution, write in the comments, although judging by Stack Overflow, the problem exists for years and all do not care). But it turned out that we don’t need it - the RDS decoder has already been added to GNU Radio, so from the project on github we need only examples that are in the apps folder.
The block diagram attached in the examples is rather monstrous, moreover, when opening it, errors are displayed (blocks are marked in red).
In real life, however, everything is simpler - 2/3 of the scheme is a stereo player for FM, where L + R and LR channels are extracted from the original signal, processed and fed to the sound card. It is irrelevant to us now, so these blocks can be removed (especially since out of the box for some reason it did not work, but it was too lazy to understand). Errors occur due to the Grid Position parameter, which apparently is not supported by the Windows version, but it can be removed without problems, it does not affect the functionality.
After removing “all superfluous”, the working RDS decoder scheme looks like this:
Let's see what is there.
The source signal comes from RTL-SDR Source, the frequency is set by the freq parameter, which has the WX GUI Slider type (yes, you can create your own UI in GNU Radio, and there are basic controls). To avoid a peak at zero frequency in the center, the freq_offset parameter is used, the Frequency Xlating block shifts the frequency by this value. The WBFM Receive unit, as the name implies, performs FM demodulation, then the frequency is shifted again to allocate the RDS itself to 57KHz. The Root Cosined Filter block allocates a narrow frequency, and the MPSK decoder with parameter 2 performs BPSK decoding (RDS itself is transmitted using phase modulation with two states). RDS uses differential encoding , so the corresponding differential decoder is called, and finally the finished binary stream is fed to the RDS Decoder block (its source can be viewed on github ). After the decoder, an equally important part is the RDS parser — there are quite a few types of packages in RDS, and the parser does all the work of decoding them.
Actually that's all. The results of the decoder on KDPV and screenshots.
If someone needs to use the program in no-UI mode, you can use the FR Tap block, a more detailed description here , I personally have not tried it. If the lower bit-rate level of RDS is interesting, I considered it earlier , it can also be useful for general interest.
As usual, all successful experiments.
The original GRC file, running under Windows, under the spoiler (the frequency of the radio station only has to be changed).
In a previous article about Software Defined Radio, a question was asked how to decode RDS using GNU Radio. The RDS decoder is not so simple to create from scratch, but fortunately for us, it is already built into GNU Radio, so it’s easy to see how it works without writing a single line of code, just RTL-SDR receiver.
')
How it works, continued under the cut.
About GNU Radio and its installation, I will not repeat, it has already been described earlier . In short, the distribution under Windows can be found here . Let's go over to the RDS itself.
If someone suddenly does not know, RDS (Radio Data System) is a protocol used in ordinary FM broadcasting to transmit additional digital information (time, exchange rates, weather, etc.). The transmission goes at a speed of 1187.5bps at a frequency of 57KHz (3rd harmonic of the pilot tone), to minimize the frequency band, BPSK (Binary Phase Shift Keying) phase coding is used. The RDS bit level has already been considered in the Habré earlier , well, we move on to GNU Radio.
The decoder for GNU Radio was made about 10 years ago , but that version is already useless to watch, the names of many units have changed, and the examples cited there no longer work. Updated fork can be taken from here .
By the way, it didn’t work to compile gr-rds from source files for Windows - cmake produces errors for the absence of Boost, although it is installed. It is not clear by the way why over the years of cmake and boost, cmake has not been taught to find ways in Windows - like finding a folder on the disk is not a rocket science at all (if anyone knows the solution, write in the comments, although judging by Stack Overflow, the problem exists for years and all do not care). But it turned out that we don’t need it - the RDS decoder has already been added to GNU Radio, so from the project on github we need only examples that are in the apps folder.
The block diagram attached in the examples is rather monstrous, moreover, when opening it, errors are displayed (blocks are marked in red).
In real life, however, everything is simpler - 2/3 of the scheme is a stereo player for FM, where L + R and LR channels are extracted from the original signal, processed and fed to the sound card. It is irrelevant to us now, so these blocks can be removed (especially since out of the box for some reason it did not work, but it was too lazy to understand). Errors occur due to the Grid Position parameter, which apparently is not supported by the Windows version, but it can be removed without problems, it does not affect the functionality.
After removing “all superfluous”, the working RDS decoder scheme looks like this:
Let's see what is there.
The source signal comes from RTL-SDR Source, the frequency is set by the freq parameter, which has the WX GUI Slider type (yes, you can create your own UI in GNU Radio, and there are basic controls). To avoid a peak at zero frequency in the center, the freq_offset parameter is used, the Frequency Xlating block shifts the frequency by this value. The WBFM Receive unit, as the name implies, performs FM demodulation, then the frequency is shifted again to allocate the RDS itself to 57KHz. The Root Cosined Filter block allocates a narrow frequency, and the MPSK decoder with parameter 2 performs BPSK decoding (RDS itself is transmitted using phase modulation with two states). RDS uses differential encoding , so the corresponding differential decoder is called, and finally the finished binary stream is fed to the RDS Decoder block (its source can be viewed on github ). After the decoder, an equally important part is the RDS parser — there are quite a few types of packages in RDS, and the parser does all the work of decoding them.
Actually that's all. The results of the decoder on KDPV and screenshots.
If someone needs to use the program in no-UI mode, you can use the FR Tap block, a more detailed description here , I personally have not tried it. If the lower bit-rate level of RDS is interesting, I considered it earlier , it can also be useful for general interest.
As usual, all successful experiments.
The original GRC file, running under Windows, under the spoiler (the frequency of the radio station only has to be changed).
rds_rx.grc
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</param> <param> <key>label</key> <value>RF Gain</value> </param> <param> <key>max</key> <value>49.6</value> </param> <param> <key>min</key> <value>0</value> </param> <param> <key>notebook</key> <value></value> </param> <param> <key>num_steps</key> <value>124</value> </param> <param> <key>style</key> <value>wx.SL_HORIZONTAL</value> </param> </block> <block> <key>variable</key> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(8, 92)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>samp_rate</value> </param> <param> <key>value</key> <value>1000000</value> </param> </block> <block> <key>variable</key> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(336, 132)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>xlate_bandwidth</value> </param> <param> <key>value</key> <value>100000</value> </param> </block> <block> <key>analog_wfm_rcv</key> <param> <key>audio_decimation</key> <value>bb_decim</value> </param> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(576, 356)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>analog_wfm_rcv_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>quad_rate</key> <value>samp_rate</value> </param> </block> <block> <key>blocks_complex_to_real</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(792, 632)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_complex_to_real_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>vlen</key> <value>1</value> </param> </block> <block> <key>blocks_keep_one_in_n</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(280, 788)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>blocks_keep_one_in_n_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>n</key> <value>2</value> </param> <param> <key>type</key> <value>byte</value> </param> <param> <key>vlen</key> <value>1</value> </param> </block> <block> <key>digital_binary_slicer_fb</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(112, 792)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>digital_binary_slicer_fb_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> </block> <block> <key>digital_diff_decoder_bb</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> 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</param> <param> <key>fmax</key> <value>0.06</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>fmin</key> <value>-0.06</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>mu</key> <value>0.5</value> </param> <param> <key>omega_relative_limit</key> <value>0.005</value> </param> <param> <key>omega</key> <value>samp_rate/bb_decim/audio_decim/ 2375.0</value> </param> <param> <key>theta</key> <value>0</value> </param> </block> <block> <key>freq_xlating_fir_filter_xxx</key> <param> <key>alias</key> <value></value> </param> <param> <key>center_freq</key> <value>freq_offset</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>decim</key> <value>1</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(279, 296)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> 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</block> <block> <key>gr_rds_panel</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>freq</key> <value>freq</value> </param> <param> <key>_coordinate</key> <value>(984, 792)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>grid_pos</key> <value></value> </param> <param> <key>id</key> <value>gr_rds_panel_0</value> </param> <param> <key>notebook</key> <value></value> </param> </block> <block> <key>gr_rds_parser</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>debug</key> <value>False</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(800, 772)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>gr_rds_parser_0</value> </param> <param> <key>log</key> <value>True</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>pty_locale</key> <value>0</value> </param> <param> <key>reset</key> <value>0</value> </param> </block> <block> <key>import</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(576, 4)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>import_0</value> </param> <param> <key>import</key> <value>import math</value> </param> </block> <block> <key>notebook</key> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(184, 6)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>grid_pos</key> <value></value> </param> <param> <key>id</key> <value>nb</value> </param> <param> <key>labels</key> <value>['BB', 'Demod', 'L+R', 'Pilot', 'DSBSC', 'RDS', 'L-R', 'RDS constellation','Waterfall']</value> </param> <param> <key>notebook</key> <value></value> </param> <param> <key>style</key> <value>wx.NB_TOP</value> </param> </block> <block> <key>root_raised_cosine_filter</key> <param> <key>alpha</key> <value>1</value> </param> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>decim</key> <value>1</value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>type</key> <value>fir_filter_ccf</value> </param> <param> <key>_coordinate</key> <value>(304, 516)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>gain</key> <value>1</value> </param> <param> <key>id</key> <value>root_raised_cosine_filter_0</value> </param> <param> <key>interp</key> <value>1</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>ntaps</key> <value>100</value> </param> <param> <key>samp_rate</key> <value>samp_rate/bb_decim/audio_decim</value> </param> <param> <key>sym_rate</key> <value>2375</value> </param> </block> <block> <key>rtlsdr_source</key> <param> <key>alias</key> <value></value> </param> <param> <key>ant0</key> <value></value> </param> <param> <key>bb_gain0</key> <value>20</value> </param> <param> <key>bw0</key> <value>0</value> </param> <param> <key>dc_offset_mode0</key> <value>0</value> </param> <param> <key>corr0</key> <value>0</value> </param> <param> <key>freq0</key> <value>freq_tune</value> </param> <param> <key>gain_mode0</key> <value>False</value> </param> <param> <key>if_gain0</key> <value>20</value> </param> <param> <key>iq_balance_mode0</key> <value>0</value> </param> <param> <key>gain0</key> <value>gain</value> </param> <param> <key>ant10</key> <value></value> </param> <param> <key>bb_gain10</key> <value>20</value> </param> <param> <key>bw10</key> <value>0</value> </param> <param> <key>dc_offset_mode10</key> <value>0</value> </param> <param> <key>corr10</key> <value>0</value> </param> <param> <key>freq10</key> <value>100e6</value> </param> <param> <key>gain_mode10</key> <value>False</value> </param> <param> <key>if_gain10</key> <value>20</value> </param> <param> <key>iq_balance_mode10</key> <value>0</value> </param> <param> <key>gain10</key> <value>10</value> </param> <param> <key>ant11</key> <value></value> </param> <param> <key>bb_gain11</key> <value>20</value> </param> <param> <key>bw11</key> <value>0</value> </param> <param> <key>dc_offset_mode11</key> <value>0</value> </param> <param> <key>corr11</key> <value>0</value> </param> <param> <key>freq11</key> <value>100e6</value> </param> <param> <key>gain_mode11</key> <value>False</value> </param> <param> <key>if_gain11</key> <value>20</value> </param> <param> <key>iq_balance_mode11</key> <value>0</value> </param> <param> <key>gain11</key> <value>10</value> </param> <param> <key>ant12</key> <value></value> </param> <param> <key>bb_gain12</key> <value>20</value> </param> <param> <key>bw12</key> <value>0</value> </param> <param> <key>dc_offset_mode12</key> <value>0</value> </param> <param> <key>corr12</key> <value>0</value> </param> <param> <key>freq12</key> <value>100e6</value> </param> <param> <key>gain_mode12</key> <value>False</value> </param> <param> <key>if_gain12</key> <value>20</value> </param> <param> <key>iq_balance_mode12</key> <value>0</value> </param> <param> <key>gain12</key> <value>10</value> </param> <param> <key>ant13</key> <value></value> </param> <param> <key>bb_gain13</key> <value>20</value> </param> <param> <key>bw13</key> <value>0</value> </param> <param> <key>dc_offset_mode13</key> <value>0</value> </param> <param> <key>corr13</key> <value>0</value> </param> <param> <key>freq13</key> <value>100e6</value> </param> <param> <key>gain_mode13</key> <value>False</value> </param> <param> <key>if_gain13</key> <value>20</value> </param> <param> <key>iq_balance_mode13</key> <value>0</value> </param> <param> <key>gain13</key> <value>10</value> </param> <param> <key>ant14</key> <value></value> </param> <param> <key>bb_gain14</key> <value>20</value> </param> <param> <key>bw14</key> <value>0</value> </param> <param> <key>dc_offset_mode14</key> <value>0</value> </param> <param> <key>corr14</key> <value>0</value> </param> <param> <key>freq14</key> <value>100e6</value> </param> <param> <key>gain_mode14</key> <value>False</value> </param> <param> <key>if_gain14</key> <value>20</value> </param> <param> <key>iq_balance_mode14</key> <value>0</value> </param> <param> <key>gain14</key> <value>10</value> </param> <param> <key>ant15</key> <value></value> </param> <param> <key>bb_gain15</key> <value>20</value> </param> <param> <key>bw15</key> <value>0</value> </param> <param> <key>dc_offset_mode15</key> <value>0</value> </param> <param> <key>corr15</key> <value>0</value> </param> <param> <key>freq15</key> <value>100e6</value> </param> <param> <key>gain_mode15</key> <value>False</value> </param> <param> <key>if_gain15</key> <value>20</value> </param> <param> <key>iq_balance_mode15</key> <value>0</value> </param> <param> <key>gain15</key> <value>10</value> </param> <param> <key>ant16</key> <value></value> </param> <param> <key>bb_gain16</key> <value>20</value> </param> <param> <key>bw16</key> <value>0</value> </param> <param> <key>dc_offset_mode16</key> <value>0</value> </param> <param> <key>corr16</key> <value>0</value> </param> <param> <key>freq16</key> <value>100e6</value> </param> <param> <key>gain_mode16</key> <value>False</value> </param> <param> <key>if_gain16</key> <value>20</value> </param> <param> <key>iq_balance_mode16</key> <value>0</value> </param> <param> <key>gain16</key> <value>10</value> </param> <param> <key>ant17</key> <value></value> </param> <param> <key>bb_gain17</key> <value>20</value> </param> <param> <key>bw17</key> <value>0</value> </param> <param> <key>dc_offset_mode17</key> <value>0</value> </param> <param> <key>corr17</key> <value>0</value> </param> <param> <key>freq17</key> <value>100e6</value> </param> <param> <key>gain_mode17</key> <value>False</value> </param> <param> <key>if_gain17</key> <value>20</value> </param> <param> <key>iq_balance_mode17</key> <value>0</value> </param> <param> <key>gain17</key> <value>10</value> </param> <param> <key>ant18</key> <value></value> </param> <param> <key>bb_gain18</key> <value>20</value> </param> <param> <key>bw18</key> <value>0</value> </param> <param> <key>dc_offset_mode18</key> <value>0</value> </param> <param> <key>corr18</key> <value>0</value> </param> <param> <key>freq18</key> <value>100e6</value> </param> <param> <key>gain_mode18</key> <value>False</value> </param> <param> <key>if_gain18</key> <value>20</value> </param> <param> <key>iq_balance_mode18</key> <value>0</value> </param> <param> <key>gain18</key> <value>10</value> </param> <param> <key>ant19</key> <value></value> </param> <param> <key>bb_gain19</key> <value>20</value> </param> <param> <key>bw19</key> <value>0</value> </param> <param> <key>dc_offset_mode19</key> <value>0</value> </param> <param> <key>corr19</key> <value>0</value> </param> <param> <key>freq19</key> <value>100e6</value> </param> <param> <key>gain_mode19</key> <value>False</value> </param> <param> <key>if_gain19</key> <value>20</value> </param> <param> <key>iq_balance_mode19</key> <value>0</value> </param> <param> <key>gain19</key> <value>10</value> </param> <param> <key>ant1</key> <value></value> </param> <param> <key>bb_gain1</key> <value>20</value> </param> <param> <key>bw1</key> <value>0</value> </param> <param> <key>dc_offset_mode1</key> <value>0</value> </param> <param> <key>corr1</key> <value>0</value> </param> <param> <key>freq1</key> <value>100e6</value> </param> <param> <key>gain_mode1</key> <value>False</value> </param> <param> <key>if_gain1</key> <value>20</value> </param> <param> <key>iq_balance_mode1</key> <value>0</value> </param> <param> <key>gain1</key> <value>10</value> </param> <param> <key>ant20</key> <value></value> </param> <param> <key>bb_gain20</key> <value>20</value> </param> <param> <key>bw20</key> <value>0</value> </param> <param> <key>dc_offset_mode20</key> <value>0</value> </param> <param> <key>corr20</key> <value>0</value> </param> <param> <key>freq20</key> <value>100e6</value> </param> <param> <key>gain_mode20</key> <value>False</value> </param> <param> <key>if_gain20</key> <value>20</value> </param> <param> <key>iq_balance_mode20</key> <value>0</value> </param> <param> <key>gain20</key> <value>10</value> </param> <param> <key>ant21</key> <value></value> </param> <param> <key>bb_gain21</key> <value>20</value> </param> <param> <key>bw21</key> <value>0</value> </param> <param> <key>dc_offset_mode21</key> <value>0</value> </param> <param> <key>corr21</key> <value>0</value> </param> <param> <key>freq21</key> <value>100e6</value> </param> <param> <key>gain_mode21</key> <value>False</value> </param> <param> <key>if_gain21</key> <value>20</value> </param> <param> <key>iq_balance_mode21</key> <value>0</value> </param> <param> <key>gain21</key> <value>10</value> </param> <param> <key>ant22</key> <value></value> </param> <param> <key>bb_gain22</key> <value>20</value> </param> <param> <key>bw22</key> <value>0</value> </param> <param> <key>dc_offset_mode22</key> <value>0</value> </param> <param> <key>corr22</key> <value>0</value> </param> <param> <key>freq22</key> <value>100e6</value> </param> <param> <key>gain_mode22</key> <value>False</value> </param> <param> <key>if_gain22</key> <value>20</value> </param> <param> <key>iq_balance_mode22</key> <value>0</value> </param> <param> <key>gain22</key> <value>10</value> </param> <param> <key>ant23</key> <value></value> </param> <param> <key>bb_gain23</key> <value>20</value> </param> <param> <key>bw23</key> <value>0</value> </param> <param> <key>dc_offset_mode23</key> <value>0</value> </param> <param> <key>corr23</key> <value>0</value> </param> <param> <key>freq23</key> <value>100e6</value> </param> <param> <key>gain_mode23</key> <value>False</value> </param> <param> <key>if_gain23</key> <value>20</value> </param> <param> <key>iq_balance_mode23</key> <value>0</value> </param> <param> <key>gain23</key> <value>10</value> </param> <param> <key>ant24</key> <value></value> </param> <param> <key>bb_gain24</key> <value>20</value> </param> <param> <key>bw24</key> <value>0</value> </param> <param> <key>dc_offset_mode24</key> <value>0</value> </param> <param> <key>corr24</key> <value>0</value> </param> <param> <key>freq24</key> <value>100e6</value> </param> <param> <key>gain_mode24</key> <value>False</value> </param> <param> <key>if_gain24</key> <value>20</value> </param> <param> <key>iq_balance_mode24</key> <value>0</value> </param> <param> <key>gain24</key> <value>10</value> </param> <param> <key>ant25</key> <value></value> </param> <param> <key>bb_gain25</key> <value>20</value> </param> <param> <key>bw25</key> <value>0</value> </param> <param> <key>dc_offset_mode25</key> <value>0</value> </param> <param> <key>corr25</key> <value>0</value> </param> <param> <key>freq25</key> <value>100e6</value> </param> <param> <key>gain_mode25</key> <value>False</value> </param> <param> <key>if_gain25</key> <value>20</value> </param> <param> <key>iq_balance_mode25</key> <value>0</value> </param> <param> <key>gain25</key> <value>10</value> </param> <param> <key>ant26</key> <value></value> </param> <param> <key>bb_gain26</key> <value>20</value> </param> <param> <key>bw26</key> <value>0</value> </param> <param> <key>dc_offset_mode26</key> <value>0</value> </param> <param> <key>corr26</key> <value>0</value> </param> <param> <key>freq26</key> <value>100e6</value> </param> <param> <key>gain_mode26</key> <value>False</value> </param> <param> <key>if_gain26</key> <value>20</value> </param> <param> <key>iq_balance_mode26</key> <value>0</value> </param> <param> <key>gain26</key> <value>10</value> </param> <param> <key>ant27</key> <value></value> </param> <param> <key>bb_gain27</key> <value>20</value> </param> <param> <key>bw27</key> <value>0</value> </param> <param> <key>dc_offset_mode27</key> <value>0</value> </param> <param> <key>corr27</key> <value>0</value> </param> <param> <key>freq27</key> <value>100e6</value> </param> <param> <key>gain_mode27</key> <value>False</value> </param> <param> <key>if_gain27</key> <value>20</value> </param> <param> <key>iq_balance_mode27</key> <value>0</value> </param> <param> <key>gain27</key> <value>10</value> </param> <param> <key>ant28</key> <value></value> </param> <param> <key>bb_gain28</key> <value>20</value> </param> <param> <key>bw28</key> <value>0</value> </param> <param> <key>dc_offset_mode28</key> <value>0</value> </param> <param> <key>corr28</key> <value>0</value> </param> <param> <key>freq28</key> <value>100e6</value> </param> <param> <key>gain_mode28</key> <value>False</value> </param> <param> <key>if_gain28</key> <value>20</value> </param> <param> <key>iq_balance_mode28</key> <value>0</value> </param> <param> <key>gain28</key> <value>10</value> </param> <param> <key>ant29</key> <value></value> </param> <param> <key>bb_gain29</key> <value>20</value> </param> <param> <key>bw29</key> <value>0</value> </param> <param> <key>dc_offset_mode29</key> <value>0</value> </param> <param> <key>corr29</key> <value>0</value> </param> <param> <key>freq29</key> <value>100e6</value> </param> <param> <key>gain_mode29</key> <value>False</value> </param> <param> <key>if_gain29</key> <value>20</value> </param> <param> <key>iq_balance_mode29</key> <value>0</value> </param> <param> <key>gain29</key> <value>10</value> </param> <param> <key>ant2</key> <value></value> </param> <param> <key>bb_gain2</key> <value>20</value> </param> <param> <key>bw2</key> <value>0</value> </param> <param> <key>dc_offset_mode2</key> <value>0</value> </param> <param> <key>corr2</key> <value>0</value> </param> <param> <key>freq2</key> <value>100e6</value> </param> <param> <key>gain_mode2</key> <value>False</value> </param> <param> <key>if_gain2</key> <value>20</value> </param> <param> <key>iq_balance_mode2</key> <value>0</value> </param> <param> <key>gain2</key> <value>10</value> </param> <param> <key>ant30</key> <value></value> </param> <param> <key>bb_gain30</key> <value>20</value> </param> <param> <key>bw30</key> <value>0</value> </param> <param> <key>dc_offset_mode30</key> <value>0</value> </param> <param> <key>corr30</key> <value>0</value> </param> <param> <key>freq30</key> <value>100e6</value> </param> <param> <key>gain_mode30</key> <value>False</value> </param> <param> <key>if_gain30</key> <value>20</value> </param> <param> <key>iq_balance_mode30</key> <value>0</value> </param> <param> <key>gain30</key> <value>10</value> </param> <param> <key>ant31</key> <value></value> </param> <param> <key>bb_gain31</key> <value>20</value> </param> <param> <key>bw31</key> <value>0</value> </param> <param> <key>dc_offset_mode31</key> <value>0</value> </param> <param> <key>corr31</key> <value>0</value> </param> <param> <key>freq31</key> <value>100e6</value> </param> <param> <key>gain_mode31</key> <value>False</value> </param> <param> <key>if_gain31</key> <value>20</value> </param> <param> <key>iq_balance_mode31</key> <value>0</value> </param> <param> <key>gain31</key> <value>10</value> </param> <param> <key>ant3</key> <value></value> </param> <param> <key>bb_gain3</key> <value>20</value> </param> <param> <key>bw3</key> <value>0</value> </param> <param> <key>dc_offset_mode3</key> <value>0</value> </param> <param> <key>corr3</key> <value>0</value> </param> <param> <key>freq3</key> <value>100e6</value> </param> <param> <key>gain_mode3</key> <value>False</value> </param> <param> <key>if_gain3</key> <value>20</value> </param> <param> <key>iq_balance_mode3</key> <value>0</value> </param> <param> <key>gain3</key> <value>10</value> </param> <param> <key>ant4</key> <value></value> </param> <param> <key>bb_gain4</key> <value>20</value> </param> <param> <key>bw4</key> <value>0</value> </param> <param> <key>dc_offset_mode4</key> <value>0</value> </param> <param> <key>corr4</key> <value>0</value> </param> <param> <key>freq4</key> <value>100e6</value> </param> <param> <key>gain_mode4</key> <value>False</value> </param> <param> <key>if_gain4</key> <value>20</value> </param> <param> <key>iq_balance_mode4</key> <value>0</value> </param> <param> <key>gain4</key> <value>10</value> </param> <param> <key>ant5</key> <value></value> </param> <param> <key>bb_gain5</key> <value>20</value> </param> <param> <key>bw5</key> <value>0</value> </param> <param> <key>dc_offset_mode5</key> <value>0</value> </param> <param> <key>corr5</key> <value>0</value> </param> <param> <key>freq5</key> <value>100e6</value> </param> <param> <key>gain_mode5</key> <value>False</value> </param> <param> <key>if_gain5</key> <value>20</value> </param> <param> <key>iq_balance_mode5</key> <value>0</value> </param> <param> <key>gain5</key> <value>10</value> </param> <param> <key>ant6</key> <value></value> </param> <param> <key>bb_gain6</key> <value>20</value> </param> <param> <key>bw6</key> <value>0</value> </param> <param> <key>dc_offset_mode6</key> <value>0</value> </param> <param> <key>corr6</key> <value>0</value> </param> <param> <key>freq6</key> <value>100e6</value> </param> <param> <key>gain_mode6</key> <value>False</value> </param> <param> <key>if_gain6</key> <value>20</value> </param> <param> <key>iq_balance_mode6</key> <value>0</value> </param> <param> <key>gain6</key> <value>10</value> </param> <param> <key>ant7</key> <value></value> </param> <param> <key>bb_gain7</key> <value>20</value> </param> <param> <key>bw7</key> <value>0</value> </param> <param> <key>dc_offset_mode7</key> <value>0</value> </param> <param> <key>corr7</key> <value>0</value> </param> <param> <key>freq7</key> <value>100e6</value> </param> <param> <key>gain_mode7</key> <value>False</value> </param> <param> <key>if_gain7</key> <value>20</value> </param> <param> <key>iq_balance_mode7</key> <value>0</value> </param> <param> <key>gain7</key> <value>10</value> </param> <param> <key>ant8</key> <value></value> </param> <param> <key>bb_gain8</key> <value>20</value> </param> <param> <key>bw8</key> <value>0</value> </param> <param> <key>dc_offset_mode8</key> <value>0</value> </param> <param> <key>corr8</key> <value>0</value> </param> <param> <key>freq8</key> <value>100e6</value> </param> <param> <key>gain_mode8</key> <value>False</value> </param> <param> <key>if_gain8</key> <value>20</value> </param> <param> <key>iq_balance_mode8</key> <value>0</value> </param> <param> <key>gain8</key> <value>10</value> </param> <param> <key>ant9</key> <value></value> </param> <param> <key>bb_gain9</key> <value>20</value> </param> <param> <key>bw9</key> <value>0</value> </param> <param> <key>dc_offset_mode9</key> <value>0</value> </param> <param> <key>corr9</key> <value>0</value> </param> <param> <key>freq9</key> <value>100e6</value> </param> <param> <key>gain_mode9</key> <value>False</value> </param> <param> <key>if_gain9</key> <value>20</value> </param> <param> <key>iq_balance_mode9</key> <value>0</value> </param> <param> <key>gain9</key> <value>10</value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>args</key> <value></value> </param> <param> <key>_enabled</key> <value>1</value> </param> <param> <key>_coordinate</key> <value>(24, 272)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>id</key> <value>rtlsdr_source_0</value> </param> <param> <key>maxoutbuf</key> <value>0</value> </param> <param> <key>clock_source0</key> <value></value> </param> <param> <key>time_source0</key> <value></value> </param> <param> <key>clock_source1</key> <value></value> </param> <param> <key>time_source1</key> <value></value> </param> <param> <key>clock_source2</key> <value></value> </param> <param> <key>time_source2</key> <value></value> </param> <param> <key>clock_source3</key> <value></value> </param> <param> <key>time_source3</key> <value></value> </param> <param> <key>clock_source4</key> <value></value> </param> <param> <key>time_source4</key> <value></value> </param> <param> <key>clock_source5</key> <value></value> </param> <param> <key>time_source5</key> <value></value> </param> <param> <key>clock_source6</key> <value></value> </param> <param> <key>time_source6</key> <value></value> </param> <param> <key>clock_source7</key> <value></value> </param> <param> <key>time_source7</key> <value></value> </param> <param> <key>minoutbuf</key> <value>0</value> </param> <param> <key>nchan</key> <value>1</value> </param> <param> <key>num_mboards</key> <value>1</value> </param> <param> <key>type</key> <value>fc32</value> </param> <param> <key>sample_rate</key> <value>samp_rate</value> </param> <param> <key>sync</key> <value></value> </param> </block> <block> <key>wxgui_fftsink2</key> <param> <key>avg_alpha</key> <value>0.8</value> </param> <param> <key>average</key> <value>True</value> </param> <param> <key>baseband_freq</key> <value>0</value> </param> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>fft_size</key> <value>1024</value> </param> <param> <key>freqvar</key> <value>None</value> </param> <param> <key>_coordinate</key> <value>(1056, 56)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>grid_pos</key> <value></value> </param> <param> <key>id</key> <value>wxgui_fftsink2_0</value> </param> <param> <key>notebook</key> <value>nb, 0</value> </param> <param> <key>peak_hold</key> <value>False</value> </param> <param> <key>ref_level</key> <value>-30</value> </param> <param> <key>ref_scale</key> <value>2.0</value> </param> <param> <key>fft_rate</key> <value>15</value> </param> <param> <key>samp_rate</key> <value>samp_rate</value> </param> <param> <key>title</key> <value>Baseband</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>win_size</key> <value></value> </param> <param> <key>win</key> <value>None</value> </param> <param> <key>y_divs</key> <value>10</value> </param> <param> <key>y_per_div</key> <value>10</value> </param> </block> <block> <key>wxgui_fftsink2</key> <param> <key>avg_alpha</key> <value>0.8</value> </param> <param> <key>average</key> <value>True</value> </param> <param> <key>baseband_freq</key> <value>0</value> </param> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>fft_size</key> <value>1024</value> </param> <param> <key>freqvar</key> <value>None</value> </param> <param> <key>_coordinate</key> <value>(1056, 280)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>grid_pos</key> <value></value> </param> <param> <key>id</key> <value>wxgui_fftsink2_0_0</value> </param> <param> <key>notebook</key> <value>nb, 1</value> </param> <param> <key>peak_hold</key> <value>False</value> </param> <param> <key>ref_level</key> <value>0</value> </param> <param> <key>ref_scale</key> <value>2.0</value> </param> <param> <key>fft_rate</key> <value>15</value> </param> <param> <key>samp_rate</key> <value>baseband_rate</value> </param> <param> <key>title</key> <value>FM Demod</value> </param> <param> <key>type</key> <value>float</value> </param> <param> <key>win_size</key> <value></value> </param> <param> <key>win</key> <value>None</value> </param> <param> <key>y_divs</key> <value>10</value> </param> <param> <key>y_per_div</key> <value>10</value> </param> </block> <block> <key>wxgui_scopesink2</key> <param> <key>ac_couple</key> <value>False</value> </param> <param> <key>alias</key> <value></value> </param> <param> <key>comment</key> <value></value> </param> <param> <key>affinity</key> <value></value> </param> <param> <key>_enabled</key> <value>True</value> </param> <param> <key>_coordinate</key> <value>(1056, 500)</value> </param> <param> <key>_rotation</key> <value>0</value> </param> <param> <key>grid_pos</key> <value></value> </param> <param> <key>id</key> <value>wxgui_scopesink2_1</value> </param> <param> <key>notebook</key> <value>nb,7</value> </param> <param> <key>num_inputs</key> <value>1</value> </param> <param> <key>samp_rate</key> <value>2375</value> </param> <param> <key>t_scale</key> <value>0</value> </param> <param> <key>title</key> <value>Scope Plot</value> </param> <param> <key>trig_mode</key> <value>wxgui.TRIG_MODE_AUTO</value> </param> <param> <key>type</key> <value>complex</value> </param> <param> <key>v_offset</key> <value>0</value> </param> <param> <key>v_scale</key> <value>0.4</value> </param> <param> <key>win_size</key> <value></value> </param> <param> <key>xy_mode</key> <value>True</value> </param> <param> <key>y_axis_label</key> <value>Counts</value> </param> </block> <connection> <source_block_id>analog_wfm_rcv_0</source_block_id> <sink_block_id>freq_xlating_fir_filter_xxx_1</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>analog_wfm_rcv_0</source_block_id> <sink_block_id>wxgui_fftsink2_0_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_complex_to_real_0</source_block_id> <sink_block_id>digital_binary_slicer_fb_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>blocks_keep_one_in_n_0</source_block_id> <sink_block_id>digital_diff_decoder_bb_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>digital_binary_slicer_fb_0</source_block_id> <sink_block_id>blocks_keep_one_in_n_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>digital_diff_decoder_bb_0</source_block_id> <sink_block_id>gr_rds_decoder_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>digital_mpsk_receiver_cc_0</source_block_id> <sink_block_id>blocks_complex_to_real_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>digital_mpsk_receiver_cc_0</source_block_id> <sink_block_id>wxgui_scopesink2_1</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>freq_xlating_fir_filter_xxx_0</source_block_id> <sink_block_id>analog_wfm_rcv_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>freq_xlating_fir_filter_xxx_0</source_block_id> <sink_block_id>wxgui_fftsink2_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>freq_xlating_fir_filter_xxx_1</source_block_id> <sink_block_id>root_raised_cosine_filter_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>gr_rds_decoder_0</source_block_id> <sink_block_id>gr_rds_parser_0</sink_block_id> <source_key>out</source_key> <sink_key>in</sink_key> </connection> <connection> <source_block_id>gr_rds_parser_0</source_block_id> <sink_block_id>gr_rds_panel_0</sink_block_id> <source_key>out</source_key> <sink_key>in</sink_key> </connection> <connection> <source_block_id>root_raised_cosine_filter_0</source_block_id> <sink_block_id>digital_mpsk_receiver_cc_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> <connection> <source_block_id>rtlsdr_source_0</source_block_id> <sink_block_id>freq_xlating_fir_filter_xxx_0</sink_block_id> <source_key>0</source_key> <sink_key>0</sink_key> </connection> </flow_graph> Source: https://habr.com/ru/post/456184/
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