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Thread: DVBT Feeder Gain Adjustment - WIP

  1. #1
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    DVBT Feeder Gain Adjustment - WIP

    WARNING:
    This should ONLY be performed if you KNOW the adjustments will assist in signal quality/range of the default setup
    (or you will no doubt be asking how to fix detrimental changes in signal/range soon after)

    For some reason the question has started to pop up again, and the more it does the more the previous explanations seem to get buried for those who search for it.

    ABCD/wiedehopf - throw some input in here where you see fit and I'll collate and work out where/find a home for it in the hope people can reference without re-query.

    May need some of your test beds alongside mine to confirm theories.

    Default Dump1090 argument/option:
    --gain <value>

    Valid <value>:
    0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
    -10
    Last edited by Oblivian; 2019-07-21 at 11:25.
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

  2. #2
    Captain abcd567's Avatar
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    Gain setting method depends on software installed

    1. Pi24 image (has pre-installed dump1090-mutability ver 1.14)

      • Option-1:
        Open settings page in web browser
        ip-of-pi:8754/settings.html

        If the field "Process Arguments" is empty, add --gain xx in it (replace xx by the desired value of gain).

        If the field "Process Arguments" already has an entry --gain -10, replace -10 by desired value of gain.

        Click "Save" button, then click "Restart" button.
        Both these buttons are at bottom-right of settings page.

        FR24 8754 settings.png


      • Option-2:
        SSH to RPi and give following command
        Code:
        sudo nano /etc/fr24feed.ini
        Check if following line exist
        procargs="--gain -10"

        If yes, change -10 to desired value of gain

        If no, add following line
        procargs="--gain xx"

        (replace xx by gain value you want)
        Save file Ctrl+o, and close Ctrl+x

        Restart fr24feed
        Code:
        sudo ststemctl restart fr24feed

        Contents of file /etc/fr24feed.ini
        (pi24-2.1.0.img)
        DEFAULT AFTER CHANGING GAIN
        bs=yes
        raw=yes
        mlat="yes"
        mlat-without-gps="yes"
        logmode="2"
        receiver="dvbt"
        procargs="--gain -10"
        fr24key=xxxxxxxxxxxxxxxx
        receiver=dvbt
        bs=yes
        raw=yes
        mlat="yes"
        mlat-without-gps="yes"
        logmode="2"
        receiver="dvbt"
        procargs="--gain 38"
        fr24key=xxxxxxxxxxxxxxxx
        receiver=dvbt


    2. Raspbian image with dump1090-mutability ver 1.15~dev
      SSH to RPi

      • Option-1:
        Code:
        sudo dpkg-reconfigure dump1090-mutability
        Continue pressing Enter key till you reach gain. Default value is "max". Change it to the desired value of gain.

        Restart dump1090-mutability
        Code:
        sudo systemctl restart dump1090-mutability

      • Option-2:
        Code:
        sudo nano /etc/default/dump1090-mutability
        Scroll down till you reach following line
        Gain="max"

        Change max to desired value of gain
        Save file Ctrl+o and Close Ctrl+x

        Restart dump1090-mutability
        Code:
        sudo systemctl restart dump1090-mutability


    3. Raspbian image with dump1090-fa

      SSH to RPi

      Give following command
      Code:
      sudo nano /etc/default/dump1090-fa
      It will open file for editing.
      Scroll down and in the line starting with RECEIVER_OPTIONS, change the gain value from -10 to the required value. In this example I will change it to 30.

      Line before change:
      RECEIVER_OPTIONS="–device-index 0 –gain -10 --ppm 0 --net-bo-port 30005"

      Line after change:
      RECEIVER_OPTIONS="–device-index 0 –gain 30 --ppm 0 --net-bo-port 30005"

      After changes are made as above, save changes (Ctrl+o) and close file (Ctrl+x)

      Restart dump1090-fa to implement the newly set gain value
      Code:
      sudo systemctl restart dump1090-fa
      Verify that the new value of gain is actually implemented
      Code:
      sudo systemctl status dump1090-fa -l
      The last line of output of above command will show gain actually set

      rtlsdr: tuner gain set to 29.7 dB

    4. Piaware SD card image (has pre-installed dump1090-fa)
      SSH to RPi

      To set gain to value xx, give following command:
      (Replace xx by actual value of gain you want to set)
      Code:
      sudo piaware-config rtlsdr-gain xx
      The above command will output following:
      Code:
      Set rtlsdr-gain to xx in /boot/piaware-config.txt:
      Restart dump1090-fa to implement the newly set gain value
      Code:
      sudo systemctl restart dump1090-fa
      Verify that the new value of gain is actually implemented
      Code:
      sudo systemctl status dump1090-fa -l
      Last line of output of above command
      Code:
      rtlsdr: tuner gain set to xx dB
    Last edited by abcd567; 2019-03-02 at 01:55.

  3. #3
    Captain abcd567's Avatar
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    ABOUT GAIN

    • Gain should always be a positive number (except -10).

    • Using a negetive number (except -10) sets the gain to ZERO.

    • Gain's permissible values are from 0 to 49.6

    • Gain="max" sets gain to maximum i.e. 49.6 dB

    • Gain -10 is a special setting. It does NOT set gain to -10. It switches dongle to AGC (Automatic Gain Control) mode. As the dongle is designed for TV reception, for TV, the AGC setting acts a intended. As the TV signal at any channel is fiarly constant, AGC works as intended. However since ADS-B signal is intermittent bursts, the AGC setting malfuntions and sets the gain to more than max (49.6). It normally sets gain to 52~55 dB.
    Last edited by abcd567; 2019-02-27 at 17:29.

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