Near Field EMI Probes: Any Good?

[Learnelectronics] purchased some near-field EMI probes for his tiny spectrum analyzer for about $5 on sale. Could they be any good at that price? Watch the video below and find out.

The probes arrived as a kit with four problems: three circular ones for sensing the H field and a stubby probe for sensing E fields (although the video gets this backward, by the way). There’s not much to them, but for the price, it probably isn’t worth making them yourself if your concern is the cost. Now, if you just want to make your own, we get that, too, but don’t expect to save much money.

If you want an idea of what you can do with these probes, GW Instek has an application note titled “The Brand New Concept of EMI Probes” that, of course, uses their probes.  You have to log in to view the document, but if you are handy with Google, you should be able to find a distributor with a copy of it in the open. Or, check out this article by Tektronix. You might also enjoy section 3.3.1 of Rohde and Schwarz’s white paper on the topic.

We’d really like to see these cheap probes compared to some of the higher-priced alternatives. There are also other designs we’ve seen. Whatever you are using, you ought to watch the 2020 Hackaday Remoticon workshop on debugging RF if you are interested in these probes.