A NanoVNA As A Dip Meter

A staple of the radio amateur’s arsenal of test equipment in previous decades was the dip meter. This was a variable frequency oscillator whose coil would be placed near the circuit to be tested, and which would show an abrupt current dip on a moving coil meter when its frequency matched the resonant frequency of what it was testing. For some reason the extremely useful devices seem hard to come by in 2024, so [Rick’s Ham Shack] has come along with a guide to using a nanoVNA in their place.

It’s a simple enough technique, indeed it’s a basic part of using these instruments, with a large sensor coil connected to the output port and a frequency sweep set up on the VNA. The reactance graph then shows any resonant peaks it finds in the frequency range, something easily demonstrated in the video below the break by putting a 20 meter (14 MHz) trap in the coil and seeing an immediate clear peak.

For many readers this will not be news, but for those who’ve not used a VNA before it’s a quick and easy demo of an immediate use for these extremely versatile instruments. For those of us who received our callsigns long ago it’s nothing short of miraculous that a functional VNA can be picked up at such a reasonable price, and we’d go as far as to suggest that non radio amateurs might find one useful, too. Read our review, if you’re interested.

18 thoughts on “A NanoVNA As A Dip Meter

  1. A device with billions of transistors doing the job requiring just one is hilarious. Oh, the times we live in. I suppose that “hard to come by” is relative. There are lots of old EICO, Heathkit, and Lafayette dippers in various states on ebay at any given time. Most need at least some repairs, but that can be part of the fun. The usual safety caveats apply for any line-powered tube equipment. Also, tunnel dippers are usually a hard pass for me since they are far too hard to find replacement parts for. That being said, I’ve refurbished and found happy homes for dozens of dippers over the years. There’s always one somewhere on my bench.

    This is an interesting approach, price-wise. The newer, transistor-based Heathkit dippers can command a price well above the NanoVNA if they are working well and include a full set of coils. A good Heathkit GD-1B can be had for less than $50. The most recent EICO 710 that I restored was $25 including shipping with all the coils and required about $10 of replacement parts. I’m not sure I’d buy one of the newest $300+ NanoVNA models just for this hack if I needed/wanted a dipper, but one of the older clones would probably be suitable.

    Of course, the best dipper is the one you build (or hack) yourself. I built my first one from a schematic in a 1954 radio electronics book. They are simple to make from scratch, but those air variable capacitor prices are getting out of hand these days.

    1. On the one hand, yes, you can do that scavenging and repair. And I hope that you do! You seem to enjoy it and be willing to share the knowledge. Last month I scavenged a couple hundred feet of CATV hardline, gonna make sqme antennas and baluns with that!

      On the other hand, the value proposition for a nanoVNA was never to replace a dipper, and your comment about transistor count misses that. Or you are whooshing me, but whatever,

      The nanoVNAs generate the kinds of graphs and plots textbooks show to illustrate theory, but they do it live and based on what you have them plugged in to. You don’t even need to swap devices. Leave it plugged in and switch back and forth.
      I have been using mine to learn to use my pi-network matchbox and tweak an experimental antenna. I can watch reactance along the entire HF band as I twiddle the knobs and try to force a few loops toward the center of the Smith chart. Look, I’m an autotuner with a human in the loop!

      When I develop more skill, I’ll probably repair more test equipment and even make my own. Then again, my interest is in antennas and I’m not a RF engineer! (or edy555, who made the NanoVNA and published the code, firmware, etc. so that others could build and learn – sound familiar?)

      I have watched these things fast-track learning, foster experimentation, and generally enhance the hobby because those few billion transistors cost $100 on the used market and replace $2000 of dedicated meters or $50 of dedicated meters and 1000 hours of grueling, dense learning. Pretty solid use of sand.

      The hobby won’t abandon homebrewing, but not requiring homebrewing opens the hobby to more people and allows them to specialize.
      That lower barrier to entry also allows fields to cross-pollinate! I don’t have to be an RF engineer to get on the air, so I can bring my knowledge of computer programming, statistics, and other domains to the party more quickly. (this is also why I’m glad the FCC cut the code requirement – I’m a VE with a local club probably a decade sooner than if I had to hit 25WPM!)
      And let me tell you, I look forward to demonstrating a few things to a club who… well, lets just say that the members didn’t seem interested in discussing the limitations of some new equipment they want to use. No matter, hands-on learning is better for retention anyway!

      1. I’m astonished that my mild amusement at the advance of technology and my musing as to some of my own similar explorations is taken so harshly. As I stated, “the best dipper is the one you build (or hack) yourself”. That seems like the statement of someone who is nothing but encouraging of exploration. As someone who owns five NanoVNAs and uses them in teaching high school STEM courses, I am well-acquainted with their uses and capabilities. New, used, or home-brew, I’m just happy for people making and sharing stuff.

        And yes, I do find a billion transistors doing the job of one amusing. Humor helps creativity. Mine can be a little dry. Maybe I’ll start using wry wink emoji’s to properly annotate anything meant to be read as whimsical.

    2. > The most recent EICO 710 that I restored was $25 including shipping with all the coils and required about $10 of replacement parts

      so the exact cost of NanoVNA clone

      1. More or less. It also came with a beautiful hand-made leather case that smells absolutely divine.

        There really is no reason not to have at least one NanoVNA around. Insofar as function goes, there’s no contest at all. I’ve wound up with five of them between using them in classrooms and my mild case of test equipment acquisition syndrome.

        Personally, I think the vintage dippers look prettier than the NanoVNAs, but that’s purely a matter of taste. The EICO 710 in particular has a certain charm in my display case coffee table with the old VTVMs. It is also over 60 years old and still functioning. Time will tell if the NanoVNA will last that long.

    3. Hi, I’m fellow extra class hammy, pseudo engineer, genuine nerd, salty millennial. I think the plague of living generations besides having a platform to stand on to prove one’s own superiority to random internet dwellers is that there’s a perception that the way things used to be done is somehow better. The way things used to be done aren’t better than the way things are done now; it’s that things are *different.* The running joke on HAD is “could have done it with a 555 timer.” It’s funny, because it’s true for a lot of things. Mike, you did the same thing, which discourages younger engineers from sharing and trying with the tools and technologies available to them. The constraints that were placed upon you in your heyday aren’t the same constraints that the generations that followed you are bound to. My pocket has millions of transistors in it, and it cost less than a fistful of transistors of yore. My point is, your constraints are different than the author of the article, they didn’t produce the article to say their way is better, in fact in many ways it’s a rediscovery with a novel application of available technology. My point; try hugging a fellow engineer and passing on your knowledge rather than kicking them in the teeth with how much better of an engineer you are and taking the wind out of their sails. Good engineers are a dying breed not because people don’t aspire to it, but because there is a generation of exceptional engineers telling the next generation they’ll never be good enough. 73

      1. My heavens. I think my tone and intent were missed or misstated. I never said that old ways were better or that anyone will not be good enough. I have nothing but admiration for the hack and stated that it’s a good value. My commentary was simply on the post’s statement that they are hard to come by and some mild amusement at the advance of technology. “The best dippers are the ones you build or hack yourself” is meant with nothing but encouraging to the next generation.

    1. And many of them are a bit of a gamble. The one I got on Tindie had been the best-behaved of my collection, but it was nearly $300! Hard to swallow, but used daily. I recall getting my first NanoVNA from R&L some years back for about $70, but I see a few for $35 on the other big sites today. It’s a deal that’s hard to pass up for what you get. That said, I’ve seen and had issues with the really cheap clones. Several have come across my workbench needing tidying up from poor quality control (out-of-spec parts, bad soldering, missing shielding, broken connectors, missing accessories, etc.) Another couple have had firmware problems. Large MLCCs broken by poor-quality lead-free re-flow soldering are truly the ticking time-bomb leaky electrolytic capacitors of our time.

  2. Interesting, but that coil set for €57 is ridiculously expensive. They’re very easy to diy, and to make lower frequency ones more sturdy you can use the cardboard leftover of small label rolls. The results with some practice are professional. I worked with Zebra and Dymo printers and their rolls (example: Dymo 99014) once empty give you a wonderful solid cardboard core that is excellent as a HF coil former. I’m sure most shops down the road will be happy to keep them for you if you ask.

    1. I’m going to try that out. Thanks. I’ve tended to stay away from cardboard for moisture resistance reasons, but it should work just great if kept out of super-humid areas or if the tubes have plastic coating (which I recall seeing on some thermal paper rolls). I never thought to ask nearby shops for castoffs. I’ve had good luck using old pill bottles over the years. They definitely looked homemade in the beginning. My own experiments in winding replacement sets over the years led down a deep rabbit hole in investigating the radio transparency of various plastics. Polypropylene and polystyrene are good choices. PVC turned out to be a bad choice for high frequencies. That’s a rabbit hole I heartily recommend anyone interested in RF to follow at some point.

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