Some days ago I decided to install an APRS RX-only iGate here in my apartment. The iGate simply takes the APRS signals from the air and forward them to the internet. I live almost in the center of the city and I have a free sight over the buildings. Good preconditions for a „fill-in“ iGate I thought. I had a Raspberry Pi and a cheap RTL-SDR dongle (DVB-T stick) for this purpose. Sounded like an easy job first but I received nothing within the next 12 hours. I knew that something must be wrong. In this project I learned more on designing HF-filter than on Linux and Raspbian, what actually was my aim at the beginning of this project. In this blog post I will show you, how I successfully dealt with massive QRM from two 100kw and 2 50kw radio transmitters.