While WXToImg provides support for recording the luminance modulated 2400 Hz subcarrier from an attached sound card, I was unable to get this working reliably using either Pulse or Alsa with the Loopback device on the RPi – Instead of a clean signal I observed significant discontinuities or loss of signal in the recorded data. # Replace spaces with - in the satellite name to allow it to be passedĮcho $(date -u +"%Y%^b%d-%H%M%S%Z")": Recording "$1" on "$2 > $logfileĮcho $(date -u +"%Y%^b%d-%H%M%S%Z")": Stopping" > $logfile # Place receiver control commands in this fifo (command pipe)Įcho "ERROR: Command fifo not found" > $logfile The command pipe isolates WXToImg from the receiver implementation and supports alternative system configurations and testing.
Currently the script only supports the three active NOAA POES satellites. The script only uses the satellite name and then passes hard-coded commands to a command pipe /tmp/record_noaa_cmd where they can be picked up by another program (further details below). The listing below shows the wxctl script used to control the RTL-SDR receiver. On the RPi the wxctl receiver control script should be saved to /usr/local/bin/wxctl. It is worth noting that two additional scripts appear to be supported: wxpbegin and wxpend, however I did not explore their use and I believe them to be deprecated. At pass end the satellite name is an empty string and the frequency is 0.00 (e.g. equivalent to calling wxctl “NOAA 15” 137.62 0).
At pass start the satellite name is argument 1, the frequency in MHz is argument 2, and the receiver port is argument 3 (e.g. For the “wxctl” receiver type WXToImg attempts to call a script wxctl (note the deliberate omission of “.sh”) at the start and end of each satellite pass. By using the “wxctl” receiver type it is possible to call a script to start or stop an attached receiver. WXToImg provides support for automated satellite signal recording in addition to image decoding. While this build was found to be very slow on my original RPi 1 Model B, the performance on the RPi 3 Model B is very good. By good fortune the Beta 2.11.2 ( alternative) release includes a build for ARM architectures allowing it to run on the Raspberry Pi.
Receiver Control and Image Generation relies on a combination of Linux shell scripts and the WXToImg ( alternative) (Professional Edition) signal to image decoder.
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