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Sudden ionospheric disturbance collector (sidc)
C Shell
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Sudden ionospheric disturbance collector (sidc)

Note: This is the fork of the original sidc with various improvements and bugfixes.

1. Introduction

sidc is a simple C program to monitor and record VLF signal for sudden ionospheric disturbances. It is forked from sidd program wirrten by Paul Nicholson <>

2. Installation

  • First install FFTW3 dependency from or use your favorite package manager to install fftw-devel package.

  • Install alsa-lib-devel package if you want to use alsa (optional).

  • Configure and compile the source




  • Install the source (if appliable)

    make install

  • Edit sidc.conf to suit your requirements. Select an output policy from the three available.

  • Start sidc in verbose foreground mode with the command

    ./sidc -vvf

  • The program will output peak and rms readings in the range 0.0 to 1.0 Adjust your mixer gain settings to leave a little headroom on the peak reading.

  • Plot the utility spectrum file

  • Check the data file columns are the ones you want.

  • Set your PC clock and activate your favourite time synchronisation software. Make sure it slews the clock rather than stepping the time.

  • Restart sidc in background with

    ./sidc -v

  • After a period of time, plot some of the data from the output file.

  • After a midnight crossing, make sure sidc has switched to the next output file.

3. Command line options

There are just a few command line options - most controls are in the config file.

-v Be a little more verbose with log messages. Use several -v for more detail.
-f Run in foreground. By default, sidc detaches from the process group and terminal and becomes a daemon. In foreground mode, log messages are duplicated to stderr.
-c config_file Run with a specified config file. By default, sidc looks for /etc/sidc.conf
-p pid_file Override default PID file location which is /var/run/ Pid file is created everytime this process becomes a daemon. Creation is skipped if file is not writable.

4 Miscellaneous notes

  • sidc will set the soundcard to the nearest available sample rate to that specified in sidc.conf
  • 24 bit soundcards may return data in 32 bit words. Try setting 'bits 24' and if sidc reports the mode unavailable, use 'bits 32'.
  • Make sure you have enough disk space. The example sidc.conf with 8 bands generates files of about 100Mbytes per day, which compress down to about 30Mbytes. Arrange scripts for plotting. Arrange scripts for compressing and archiving files that are a few days old.
  • Simple init scripts provided. Check the readme in init_scripts directory.
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