OpenSky Feeder for the Radarcape
Since major release 2 of the radarcape firmware, the radarcape now supports to feed to the OpenSky network out of the box.
Using the web interface of your radarcape, navigate to "Settings - Radarcape Feeder Settings - Opensky Network" and follow the instructions.
For older radarcapes, you can either update to the new major release, or follow the old instructions.