[audio is distorted - maybe due to narrowband ?]

[israelgoldstein]

Describe your environment

• RTLSDR-Airband version you are using (stable release number or branch/commit): 4.0.3
• make options used to build the program: NFM ON
• Hardware platform (eg. x86_64, Raspberry Pi v4):ThinkCentre server
• Operating system name and version: ubuntu

What happened? The wav files that's being generated sound distorted. where can i upload it ? so you can hear it

What you expected to happen? I expect it to sound clear.

Steps to Reproduce

Additional context Add any other relevant information about the problem here.

Your rtl_airband.conf file

fft_size = 1024;
localtime = true;
log_scan_activity = true;
multiple_demod_threads = true;
devices: (
  {
    disable = false;
    type = "rtlsdr";
    serial = "A11";
    gain = 25.0;
    sample_rate = 2.3;
    centerfreq = 463.41;
    channels:
    (
      {
        #disable = true;
        freq = 463.0625;
        lowpass = 3200;
        highpass = 200;
        bandwidth = 5000;
        modulation = "nfm";
        notch = 100.0;
        outputs: (
          {
            #disable = true;
            type = "file";

           directory = "/home/folder/1";
            filename_template = "CH 1";
            split_on_transmission = true;
            include_freq = true;
          },
          {
            #disable = true;
            type = "icecast";
            server = "1.server.net";
            port = 5027;
            mountpoint = "Mount_1";
            name = "CH 1";
            genre = "Live feed";
            username = "source";
            password = "password";
        }
        );
      },
      {
        #disable = true;
        freq = 463.1875;
        lowpass = 3200;
        highpass = 200;
        bandwidth = 5000;
        modulation = "nfm";
        notch = 103.5;
        outputs: (
          {
            #disable = true;
            type = "file";
            directory = "/home/folder/2";
            filename_template = "CH 2";
            split_on_transmission = true;
            include_freq = true;
          },
          {
            #disable = true;
            type = "icecast";
            server = "1.server.net";
            port = 5027;
            mountpoint = "Mount_2";
            name = "CH 2";
            genre = "Live feed";
            username = "source";
            password = "password";
        }
        );
      }
    );
  }
);

[charlie-foxtrot]

Is this a new problem or something that has always been there?

If you run with -f what are the signal and noise levels like?

Is this specific to these channels or does it happen with others as well?

You aren't setting a correction value for the SDR, have you confirmed there is no tuning error?

I don't have a specific service for uploading audio files but there are some free ones out there where you can share a file with a public link (google drive, drop box, etc)

[israelgoldstein]

I'm new to this software, and have experienced this from the beginning ,

attached is the output:

> 476.562   476.438   476.337   476.587   476.387   476.312   476.637   476.362   476.887   476.537   476.837   476.912   476.487   476.962   476.662   476.462   476.512   476.938   476.862   477.012   476.412   476.987   476.737   476.787   476.762   476.688   477.137   477.087   477.037   477.112   476.712   476.612   477.062   -51/-51  -50/-51   -50/-51   -50/-51   -50/-51   -39/-50*  -50/-51   -50/-51   -50/-51   -51/-51   -50/-51   -35/-50*  -49/-51   -50/-51   -50/-51   -51/-51   -51/  -50/-51  -50/-51   -51/-51   -51/-51   -50/-51   -39/-50*  -50/-51   -49/-51   -50/-51   -50/-51   -50/-51   -35/-50*  -50/-51   -50/-51   -51/-51   -50/-51   -50/  -19/-51* -50/-51   -50/-51   -51/-51   -50/-51   -40/-50*  -51/-51   -49/-51   -50/-51   -51/-51   -50/-51   -35/-50*  -50/-51   -50/-51   -50/-51   -26/-51*  -50/  -19/-51* -50/-51   -50/-51   -51/-51   -50/-51   -40/-50*  -51/-51   -50/-51   -50/-51   -51/-51   -50/-51   -35/-50*  -50/-51   -50/-51   -50/-51   -26/-51*  -50/  -18/-51* -50/-51   -50/-51   -50/-51   -49/-51   -40/-50*  -51/-51   -50/-51   -50/-51   -51/-51   -50/-51   -35/-50*  -51/-51   -50/-51   -50/-51   -26/-51*  -50/ -50/-51   -50/-51   -50/-51   -51/-51   -50/-51   -39/-51*  -51/-51   -51/-51   -50/-51   -50/-51   -32/-50*  -35/-50*  -51/-51   -50/-51   -50/-51   -48/-51*  -50/  -50/-51  -51/-51   -50/-51   -51/-51   -50/-51   -39/-51*  -51/-51   -50/-51   -50/-51   -51/-51   -31/-50*  -36/-50*  -50/-51   -50/-51   -50/-51   -49/-51   -51/  -51/-51  -50/-51   -49/-51   -51/-51   -51/-51   -39/-51*  -51/-51   -50/-51   -50/-51   -50/-51   -31/-50*  -35/-50*  -51/-51   -50/-51   -51/-51   -50/-51   -50/  -50/-51  -50/-51   -50/-51   -51/-51   -50/-51   -40/-51*  -50/-51   -50/-51   -50/-51   -50/-51   -32/-50*  -36/-50*  -50/-51   -50/-51   -50/-51   -50/-51   -50/  -50/-51  -50/-51   -49/-51   -50/-51   -50/-51   -40/-51*  -51/-51   -50/-51   -50/-51   -50/-51   -31/-50*  -35/-50*  -51/-51   -50/-51   -51/-51   -50/-51   -50/  -51/-51  -50/-51   -50/-51   -51/-51   -50/-51   -40/-51*  -51/-51   -51/-51   -51/-51   -51/-51   -50/-50*  -35/-50*  -50/-51   -50/-51   -50/-51   -50/-51   -51/  -50/-51  -50/-51   -50/-51   -51/-51   -50/-51   -40/-50*  -50/-51   -51/-51   -51/-51   -51/-51   -51/-51   -36/-50*  -50/-51   -50/-51   -50/-51   -51/-51   -50/ -50/-51  
> -------------------------------------------------------------------------------
> 
>  464.662  
> 
>  -51/-52  
>  -51/-52  
>  -51/-52  
>  -51/-52  
>  -51/-52  
>  -50/-52  
>  -50/-52  
>  -51/-52  
>  -51/-52  
>  -51/-52  
>  -51/-52  
>  -51/-52  
> 
> -------------------------------------------------------------------------------
> 
>  470.837   470.812   470.688   470.712   470.862   470.887  
> 
>  -50/-51  -49/-51   -51/-51   -51/-51   -50/-51   -50/-51  
>  -50/-51  -50/-51   -50/-51   -50/-51   -50/-51   -49/-51  
>  -50/-51  -50/-51   -50/-51   -50/-51   -51/-51   -50/-51  
>  -50/-51  -49/-51   -51/-51   -50/-51   -50/-51   -49/-51  
>  -51/-51  -51/-51   -51/-51   -51/-51   -50/-51   -49/-51  
>  -48/-51  -49/-51   -50/-51   -51/-51   -50/-51   -50/-51  
>  -49/-51  -49/-51   -50/-51   -50/-51   -50/-51   -51/-51  
>  -50/-51  -49/-51   -51/-51   -50/-51   -50/-51   -49/-51  
>  -50/-51  -50/-51   -50/-51   -50/-51   -50/-51   -50/-51  
>  -50/-51  -49/-51   -50/-51   -50/-51   -49/-51   -50/-51  
>  -49/-51  -50/-51   -50/-51   -50/-51   -50/-51   -50/-51  
>  -49/-51  -50/-51   -50/-51   -50/-51   -50/-51   -49/-51  
> 
>  -50/-52  -50/-51   -50/-52   -50/-52   -50/-52   -49/-51   -51/-51   ---------

it seems to happen with all channels received by this device

how do i know my correction? the SDR advertises as having a good click chip, so it doesn't drift off. but i see some channels are off, for example 470.688 when its supposed to be 470.687

[charlie-foxtrot]

I use SDR++ (https://www.sdrpp.org) to visualize both gain and offset adjustment. If you can find an always transmitting signal at a known frequency (ie NOAA weather in the US) you can use that to determine the correction. If your correction is +/- 2 or less then that likely is not causing your problem.

Next in SDR++ (or equivalent) tune to the center frequency you're setting and watch the signals for a while as you change the gain. You may have a strong signal on a neighboring frequency that is causing issues.

The config you posted had just 2 frequencies 463.0625 and 463.1875 while your output from running -f didn't have those frequencies but had many more. I would recommend isolating to a few channels, getting those to work, then adding more.

[charlie-foxtrot]

@israelgoldstein are you still seeing this issue? If not, please close

[israelgoldstein]

Hi, yes my audio is still distorted, i cant figure out why. i didn't get to try sdr++

[israelgoldstein]

i was able to upload a sample file to: https://file.io/sbO8bxowndai

[charlie-foxtrot]

that file looks to have been deleted, can you re-post? Also confirm this is with rtl-sdr dongles and not airspy?

[israelgoldstein]

Attached is my config file for this setup

all channels user Bandwidth set to 12500 and also streaming to icecast

fft_size = 1024;
localtime = true;
log_scan_activity = true;
multiple_demod_threads = true;
devices: (
  {
    #disable = true;
    type = "rtlsdr";
    serial = "70000701";
    gain = 39.0;
    centerfreq = 477.300;
    sample_rate = 2.4;
    channels:
    (
      #Channels Go here
    );
  },
  {
    #disable = true;
    type = "rtlsdr";
    serial = "70000702";
    gain = 35.0;
    centerfreq = 482.900;
    sample_rate = 2.4;
    channels:
    (
      #Channels Go Here
    );
  },
  {
    #disable = true;
    type = "rtlsdr";
    serial = "70000703";
    gain = 25.0;
    centerfreq = 470.100;
    sample_rate = 2.4;
    channels:
    (
      #Channels Go Here
    );
  }
);