Virtual audio devices setup
Although it is possible to stream audio from/to Raspberry Pi's audio port, I wanted to separate the QO-100 audio from all the other "normal" audio in order to avoid inadvertently transmitting system system notifications or such like.
Nowadays, for every popular OS there is a "virtual sound card" kind of software (such as Virtual Audio Cable for Windows or Loopback on macOS).
For Linux, no additional software is required (other than PulseAudio, which in Raspberry Pi OS comes installed as a default) and this is a simple matter of loading the right modules in PulseAudio.
Add the following to your /etc/pulse/default.pa
:
load-module module-null-sink sink_name=qo-100-tx
load-module module-null-sink sink_name=qo-100-rx
And restart pulseaudio:
$ sudo killall pulseaudio
Because GNU Radio supports only ALSA devices, you will also need to create the ~/.asoundrc
file with the following content:
pcm.qo-100-rx {
type pulse
device qo-100-rx
}
ctl.qo-100-rx {
type pulse
device qo-100-rx
}
pcm.qo-100-tx-monitor {
type pulse
device qo-100-tx.monitor
}
ctl.qo-100-tx-monitor {
type pulse
device qo-100-tx.monitor
}
Audio streaming
TODO
CPU overclocking
TODO
Disable WiFi
TODO
GNU Radio installation
TODO
Continue reading in Part 4 >>
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Excellent signals in IO91 in a pass starting at around 17:40 UTC.
Received using:
- Yaesu VX-7R
- QFH antenna
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Relatively low pass, from AOS to ~20 deg. elevation for this picture.
Equipment:
- FT817
- 3-el Yagi (hand-held)
- QSSTV on Fedora Linux
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After initial delay, ARISS SSTV commemorative event continues being well received across the globe. These picures were recorded on 12th April 2016 at about 20:15 UTC in IO91:
Note this pass wasn't very favourable for my location, at its highest elevation (and, conversely, the strongest signal) a 3 minute off period (when no signal is transmitted from the ISS in order to allow the gear to cool off) kicked in. Therefore in this pass I could only record the end of one image and this one in which the signal slowly drifted into white noise as the ISS was reaching my radio-horizon. Still, I'm pretty pleased with this picture.
Received using:
- Yaesu FT-857D
- Fedora linux, Gpredict and remote hamlib for radio control (Doppler)
- Raspberry Pi + Raspbian attached to radio for hamlib remote control and for audio capture
- QSSTV (learn how)
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