Software Troubleshooting Guide

When you install the OGN receiver software and things seem not to work well or at all.

Check if tasks are running

There are two tasks (processes) which should run:

  1. ogn-rf
  2. ogn-decode

You can check if they doing something by typing


which shows the list of processes and amount of CPU they take (top-CPU tasks are on top).
Normally both task should consume some CPU, at least 10-20%, if one or both consume nearly no CPU then something is wrong like RF data is not getting there.

if the task appear not to run

Check the file /etc/rtlsdr-ogn.conf with the command:

sudo nano -w /etc/rtlsdr-ogn.conf

check the user and directory where the binary is expected, as well as the configuration file name and localtion.
Normally the program is installed in default user directory in subdirectory rtlsdr-ogn-0.2.6 (0.2.6 is the version name, which will change for future releases)

if the tasks run but stop/crash due to errors

Try to identify the problem by checking the output of the suspected task.
The task can crash or can simply stop due bad format of the configuration file or lack of such.
In the latter case check which configuration file is being given to the binaries in /etc/rtlsdr.conf

If a task is crashing this can be due to privileges assigned to the executables. Try to run the provided script:


Check the output of the tasks

and look for error messages or check the dialog with the APRS server
Standard output of the ogn-rf and ogn-decode can be checked with the commands:

telnet localhost 50000  # connects to stdin/stdout of ogn-rf, Ctrl-C to exit
telnet localhost 50001  # connects to stdin/stdout of ogn-decode, Ctrl-C to exit

If telnet fails like "connection refused", then most likely the given task is not running.
If there is a problem with the RTLSDR dongle you will see message saying so on port 50000 every second.

Check the status and effective parameters

on the HTTP status page on ports 8080 and 8081 for the two tasks.
You can open these pages with any browser of the command:

lynx localhost:8080
lynx localhost:8081

Check the noise level on the 8081 page, if there is any number different from "-inf" this is a good sign: the RF data is getting there.

Check spectrograms

from HTTP status pages. If you get JPEG images with some content this is a good sign: the RF data is getting there.
If you can't get the images there is something wrong with the data chain.

Frequency tuning

Cheap RTLSDR dongle have crystal with wide frequency tolerance: the blue and black dongles are usually 60-80ppm off frequency.
This is not a major problem, because once you know how much they are off you can correct it, by setting the RF.FreqCorr parameter.

More expensive dongles like silver or orange ones have the TCXO (Temperature Compensated Crystal Oscillator) and are not more than 1-2ppm off.
These don't need correcting their frequency, you can leave the *RF.FreqOfs* off or set it to 0.

You can measure the frequency offset of your dongle with the gsm_scan utility, but first stop the OGN receiver:

sudo service rtlsdr-ogn stop # stop the OGN receiver tasks
./gsm_scan                           # run the gsm_scan utility
sudo service rtlsdr-ogn start # start the OGN receiver again
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