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  • Linux vs. Windows - very different results

    I've had a Windows-based system feeding data to FR24 for some years now and have recently (with encouragement from the site helpdesk) updated the Windows software to the latest version. It's running well, and I typically see about 370 aircraft a day.

    I've set up a parallel Linux system running Mint 18 (with help from various people here), which uses the site version of dump1090 inclulded in the Linux download. Again, it's now running well, but sees only about 250 aircraft a day.

    My question is, why the difference? The hardware set-up is identical on both systems, and while the two antennas have slightly different views of the sky, not enough to cause this sort of difference.

    I'm suspecting it's something to do with the gain setting on the RTL-SDR dongle, but how to access this? Before I installed the site software, I had a version of dump1090 running which could set gain by a command line switch, but the site software won't run alongside this version, and I haven't found any documentatiion about its command line parameters, if any. Do these dongles store their gain settings in firmware, or does gain have to be set on every run of dump1090? I'm wondering if there is a way to set the gain, and then have the site feeding software running.

  • #2
    You can specify it in the 'additional parameters' hole in config if using the malcom Robb/FR24 running decoder.

    If you installed Dump1090 separately and your config is for AVRTCP, you can reconfigure dump1090 with the option and start things up again

    Recent topic was just discussed on exactly this
    https://forum.flightradar24.com/thre...highlight=gain
    Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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    • #3
      Thank you, I'll see what I can make of the linked thread! I'm just running whatever version of dump1090 comes with the Debian package download for Linux from this site.

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      • #4
        Image or install script?

        Both should contain Malcom Robb fork that fr24 have modified. It may or may not have some optimisations applied.

        Sent from my XT1092 using Tapatalk
        Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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        • #5
          I just clicked the Linux Debian package link off the "share your data" page and it went away and did things. I had previously had another version of dump1090 installed which someone had talked me through. I really don't understand what I'm doing with Linux, and I'm frightened that if I start messing around with the gain adjustment stuff (which seems to be written for the RPi, not "mainstream" Linux) I'll just wreck the system which, after a fortnight of sweat and tears, is actually working, even if not optimally!

          Just clutching at straws:

          I'm getting this report from the service status:
          fr24feed.service - LSB: Flightradar24 Decoder & Feeder
          Loaded: loaded (/etc/init.d/fr24feed; bad; vendor preset: enabled)
          Active: active (running) since Sun 2017-07-02 14:01:10 BST; 1 weeks 0 days ago
          Docs: man:systemd-sysv-generator(8)
          Process: 1379 ExecStart=/etc/init.d/fr24feed start (code=exited, status=0/SUCCESS)
          CGroup: /system.slice/fr24feed.service
          ├─ 1406 /usr/bin/fr24feed -- --monitor-file=/dev/shm/fr24feed.txt --write-pid=/var/run/fr24feed.pid --quiet --log-base=/var/log/fr24feed --log-rotate=1
          └─17805 /usr/lib/fr24/dump1090 --raw

          Jul 02 14:01:10 arwen systemd[1]: Starting LSB: Flightradar24 Decoder & Feeder...
          Jul 02 14:01:10 arwen fr24feed[1379]: * Starting FR24 feeder fr24feed
          Jul 02 14:01:10 arwen fr24feed[1379]: ...done.
          Jul 02 14:01:10 arwen systemd[1]: Started LSB: Flightradar24 Decoder & Feeder.

          And I'm using this config file:
          receiver="dvbt"
          fr24key="*********"
          bs="yes"
          raw="yes"
          logmode="1"
          mlat="no"
          mlat-without-gps="no"

          I'm assuming that the bit I've put in bold is the switches passed to dump1090. Is there something I can put in the config file to at least turn on automatic gain control? It passes the "raw" switch OK (which I'm using to feed to VirtualRadar) like this.

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          • #6
            Goto the web config page. I'm not sure what the parameters pass as and end up with in the config file. IP of device:8754

            Sent from my XT1092 using Tapatalk
            Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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            • #7
              And no, the gain control is for dump1090. Not just pi. The pi run a branch of debian based Linux called raspian.

              Sent from my XT1092 using Tapatalk
              Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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              • #8
                OK, I've found a web config page with a box called "Process Arguments" (extra arguments for dump1090). Am I right in saying that I can add "--gain -10" in here to force AGC, or "--gain 48.0" (or similar)? If I can do it this way, I can perhaps improve things by trial and error! It may be slow but at least I'll understand what I'm doing!

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                • #9
                  Pretty much. Auto gain may be set on startup. Easy way is to send a Sudo service fr24feed stop, Sudo fr24feed start

                  Leave out.service and you get screen output. CtrlZ or use the web page to stop again.

                  The extra args may only need one '-'. You can confirm with above. Or check config.ini

                  Sent from my XT1092 using Tapatalk
                  Posts not to be taken as official support representation - Just a helpful uploader who tinkers

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                  • #10
                    OK, will play around with that for a few days! Thank you.

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