EU e-Privacy Directive

This website uses cookies to manage authentication, navigation, and other functions. By using our website, you agree that we can place these types of cookies on your device.

View e-Privacy Directive Documents

View GDPR Documents

You have declined cookies. This decision can be reversed.

SDR Box Software Diagram

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


CPU overclocking


Disable WiFi


GNU Radio installation



Continue reading in Part 4 >> 

Have you ever thought about running your own DX cluster node? I must admit for a long time I didn't use to think I needed it until recently when, in order to speed up [NKCCluster](https://www.chonky.net/nkccluster) development, it became apparent to me that a DX cluster node I could easily deploy in a CI environment would considerably speed up my development process. Although [DX Spider Installation](http://www.dxcluster.org/main/installation_en.html) is well documented, I wanted something that I could "fire & forget" and spin up a running DX cluster node in seconds. It seemed to me that a Docker image would be a very convenient way to achieve this. After some googling, I couldn't find anything on the Internet, although on GitHub there exist several repositories whose contents suggest others had similar idea (unfortunately, with no tangible results). I thus decided to develop the DX Spider Docker image myself. Although it is still in its early stage, it is already functional enough to bring up a working DX Spider node in seconds. Its source code is in GitHub repository [kconkas/dxspider-deployment](https://github.com/kconkas/dxspider-deployment) and the image itself is available in identically named [DockerHub repository](https://hub.docker.com/r/kconkas/dxspider/). Give it a try and see if you like it. GitHub pull requests and bug reports are very welcome. **Note:** this image will only get you a running DX Spider node, but will not link it with any other nodes. If you'd like to link it with another node, you will need to agree this with an owner of another active node and configure your connect file for it. You can find more details about it on the [DX Spider Wiki](http://wiki.dxcluster.org/index.php/Configuration#Connection_scripts). ### Credits Huge thanks to Dirk Koopman (G1TLH), the author of [DX Spider](http://www.dxcluster.org/main/), for this invaluable piece of software.

Excellent signals in IO91 in a pass starting at around 17:40 UTC.


Received using:

  • Yaesu VX-7R
  • QFH antenna

Relatively low pass, from AOS to ~20 deg. elevation for this picture.


  • FT817
  • 3-el Yagi (hand-held)
  • QSSTV on Fedora Linux


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)