If a picture is worth a thousand words, you might find my RFI fighting videos useful. When you can actually see spatial filtering work, you get motivated.
It’s hard to believe, but I made the first of my RFI fighting videos almost seven years ago! Since then, I have learned more (perhaps too much) about RFI and posted many articles on the subject.
Of course, the best way to fight radio frequency interference is to remove or mitigate the source, typically a switched mode power supply. If not removal, then mitigation with toroid or filter to remove common mode conduction. My house is clean. My neighborhood is not. That’s where analog or digital spatial interference filtering comes in.
For me, it all started in 2014 with the first of my RFI fighting videos Adventures with RFI. My premiere video takes you through my entire discovery, diagnosis, attempts at mitigation and finally fighting the interference with my ANC-4. Back then, my main SDR was a single channel Perseus receiver.
Fast forward to this year, and you will find that I moved on to diversity reception, using a two channel SDRplay RSPduo. This radio is a great performer for HF listening using spatial filtering. Two channels, two antennas does the trick, as shown in this RSPduo demonstration video from last summer.
In between these, I posted another of my RFI fighting videos in 2018, providing a detailed comparison of analog (ANC-4) versus diversity (two channel) noise fighting techniques.
RFI Fighting Videos – How SIFT Works
Some folks asked me for a bare metal explanation of how phasing or spatial interference filtering works. Ideally, you phase reverse your noise channel and add it to your main channel. Your result should be a desired signal with the noise removed.
My SDR Spatial Filtering demonstration was produced using a GNURadio simulation a few years ago.
All of my videos have been produced using Open Broadcaster Software, a great open-source tool. OBS is also a great way of capturing your radio computer monitors to demonstrate your ham radio and shortwave listening activities to other folks.