These days we’re surrounded by high-speed electronics and it’s no small feat that they can all play nicely in near proximity to each other. We have RF emissions standards to thank, which ensure new products don’t spew forth errant signals that would interfere with the data signals traveling through the ether. It’s long been the stuff of uber-expensive emissions testing labs, and failure to pass can leave you scratching your head. But as Alex Whittimore shows in this workshop from the 2020 Hackaday Remoticon, you can do a lot of RF emissions debugging with simple and inexpensive tools.
Once everything is hooked up and running, you wave the probes over your test board like a magic wand. Peaks will appear in the software visualization corresponding to emissions at that wavelength. Alex demonstrates starting with a large loop probe to get into the neighborhood, then swapping out probes for smaller and smaller loops to get all the way down to the pin on the chip where the signal is coming from.
The tools are cheap, the software is free, and we all should give this a try. Those lucky enough to have a HackRF in their toolkit will especially like the side-by-side comparison at the end of the workshop. It’s not surprising to see it kicking the butt of the RTL-SDR, but for basic debugging, simple tools are more than adequate to let you see what is normally unseeable.