The UPS is huge noise generator – or it should I say, it was!
In picture below, on the left hand side this is the noise generated by the UPS when running, on the right hand side UPS is inside a very simple metal mesh cage built from the stuff from the attic in half an hour. Receiver antenna was 34cm away from the UPS case and SDR was set to listen from DC to 10MHz (note the scale in the picture, I’m using HamItUp converter with 125MHz base frequency). I consider this test to be successfull 🙂
This is my second metal mesh I have built and based on the test I will cover all my computers, peripherals and other with similar cage during the next field day at my remote site.
More details what I did and how I found this can be read from my earlier post.