After a long peroid of time using Raspberry Pi as ADS-B decoder I found my good ole Emgo RX137 on the attic again.
I connected the RX to a 3$ chinese USB soundcard. Then I installed the latest beta of WXToImg on Raspian.
After testing the setup it finaly works fine.
Have a closer look at
http://qth.at/de8msh/wxtoimg/index.html
and
My setup is Raspberry Pi B, Emgo RX137, USB soundcard, DIY QFH antenna.
Thanks to WXToImg team for transporting this fine software to ARM cpu.