A dip meter is basically a coil of wire that, when you excite it, you can use to tell if something inside that coil is resonating along. This lets you measure unknown radio circuits to figure out their resonant frequency, for instance. This week, we featured a clever way to make a dip meter with a nanoVNA, which is an odd hack simply because a dip meter used to be a common spare-parts DIY device, while a vector network analyzer used to cost more than a house.
Times have changed, and for the better. Nowadays, any radio amateur can pick up a VNA for less than the cost of all but the cheesiest of walkie talkies, putting formerly exotic test equipment in the hands of untrained mortals. But what good is a fancy-pants tool if you don’t know how to use it? Our own Jenny List faced exactly this problem when she picked up a nanoVNA, and her first steps are worth following along with if you find yourself in her shoes.
All of this reminded me of an excellent series by Mike Szczys, “Scope Noob”, where he chronicled his forays into learning how to use an oscilloscope by running all of the basic functions by working through a bunch of test measurements that he already knew the answer to.
It strikes me that we could use something like this for nearly every piece of measuring equipment. Something more than just an instruction manual that walks you through what all the dials do. Something that takes you through a bunch of example projects and shows you how to use the tool in question through a handful of projects. Because these days, access to many formerly exotic pieces of measuring gear has enabled many folks to have gear they never would have had before – and all that’s missing is knowing how to drive them.
Had that exact experience with my NanoVNA. Watched a ton of YouTube videos and tried to pick up all the background needed to run the thing. Everyone assumes that you already have experience using a professional VNA, and the NanoVNA is just like that. There’s no “VNA for dummies”, at least that I could find at that time (but this was before covid, so…).
For example, you always have to calibrate your system before you save a configuration to memory; basically, any time you have a different DUT configuration or have different wires leading to your DUT you have to recalibrate to compensate for the lengths of the wire.
And calibration has something to do with the stored settings, but I don’t quite remember what. You can set up a start/end frequency and store it for later recall, but if the system isn’t calibrated at the time of storing it doesn’t work right. Or something.
I’m sure someone will jump in and explain the store/recall/ calibration thing I’m talking about, but my point is that it totally isn’t *obvious* that the stored settings require calibration, and there’s no real tutorials about VNAs and this particular VNA.
I’m reminded of lots of software packages that have user manuals that explain things like the “kerning enhance” adjustment feature, that say “click the the checkbox to activate enhanced kerning”. (And what the heck is kerning anyway, and why would I need it?)
Learning the NanoVNA was a bit of a challenge, and it’s easy to get nowhere with it and give up.
Always get a test board. It helps to be able to connect to a system with a known response just to get familiar with the system.
As someone who was trained to work with professional VNAs, I also found the support lacking practical examples. Many “why?” questions met the response “because this is the way we have always done it” or “this is what I was taught”.
Then each brand of equipment had its own nomenclature just to make things more confusing.
Well the normal way to calibrate the nanovna is basically the same as you would do when working with a scale. So unless you meant something else…
First you look at the scale while it’s empty and make sure it reads zero. Next you can put a calibrated brass weight on it and make sure the reading matches what the weight says. Then since you aren’t always just going to put things directly on the scale, you probably have a container you want to put them in, so you need to put that on the scale and tare so that the scale’s reading doesn’t include the container’s weight.
With the nanovna, you need to cancel out the coax cable “container” by taking measurements in known conditions. There’s no brass weight, but there’s a dummy load with a known value instead. There’s no “empty” but there’s a short circuit and an open circuit instead. If you want, you could imagine that one of (open or short) is zero weight and one of them is the maximum weight, even though that’s not really right.
I’d vote for an article on using old school vernier calipers and micrometers. They’re wonderful tools that really aren’t hard to read once you understand them, but particularly vernier calipers seem to be a dying art. Recently I’ve convinced a couple of friends to buy and learn them. The unique selling point for anyone who doesn’t measure things every day is that I guarantee when you need them they’ll never be out of batteries :)
I use vernier calipers with students, and the biggest issues they have are a) that different models are graduated differently, and b) the students have no clue how big anything is so mess up units and scales (inches vs cm vs mm).
Why vernier? No batteries, minimum maintenance, they don’t ever lie (either in how accurate the reading is or the value, as long as they are not seriously, visibly damaged), and the principle is fairly general. The only real maintenance is running calibration checks annually, logging the record, and replacing the tags.
I also use them, as well as standard non-digital micrometers, in my engineering practice half of my life, especially in field work, for basically the same reasons.
Agreed. I exclusively use vernier calipers like my ancestors once did and it’s nice not having to deal with batteries.
Knowledge of and practice with tools is absolutely fundamental to any form of making. Any articles that focus on tools and techniques are most welcome. I heartily believe that all makers should take time to study and practice with tools both in and outside the context of projects.
The diversity of tools and techniques is a topic worth discussing. 3d printers, CNC, and ordering boards online are only the smallest corner of an exquisite expanse of implements and methods going back past the dawn of recorded history. Making is a dance and there is artistry and expression in our tools, techniques, and materials. Even the humblest of hammers and the simplest of lathes have lessons to teach the greatest of masters. Some of making is practical. Some is not. Let us celebrate all the ways and means of making. Let us take up, in turn, each and every tool so that they may shape and inspire us.
That being said, I’d like to see some articles exploring basic technical sketching and manual drafting. As a STEM teacher, I witness every day how freely drawing our ideas in different ways has a profound impact on the quality of the things we conceive of and make. Just to be clear, I spent 5 years as a professional drafter working in CAD and I use CAD software nearly every day.
In regards to the NanoVNA, I heartily recommend the YouTube channel of the distinguished W2AEW. He has put together many excellent and practical hands-on guides using NanoVNA over the years. https://www.youtube.com/@w2aew/videos
W2AEW videos: seconded, and thirded! He has insanely deep knowledge and is a fantastic explainer to boot.
Every time I watch one, even on a topic I already “know” enough about, I learn something.
Technical sketching would be pretty interesting. I haven’t ever seen any training in that area, it seems like it was always just something that sort of came naturally to people after designing for a few years. We used to joke that a concept sketch wasn’t official unless it was on a cocktail napkin.
What with CAD doing all the hard work that used to need some degree of thought, projective geometry / orthographic projection / multiview projection is a dying art. I see people making drawings these days with views unaligned and they probably wouldn’t know first-angle from third-angle projection if the symbols reached out and slapped them in the face.
Geometric Dimensioning & Tolerancing (ASME Y14.5 / ISO GPS) is another one of those tools that deserves more discussion. It is unused, misused, or at least very poorly understood by the vast majority of engineers I have ever seen yet it is intensely critical to conveying engineering requirements for parts of complex assemblies. Even more unfortunately, it is not understood by most metrologists working in industry. There are materials to learn it well out there, but it takes a fairly curious intellect to find them and dig in enough to understand them unless one is lucky enough to get into a class from a very select few teachers.
I was taught that you always store measurement tools with metal surfaces that contact each other with a piece of food-grade wax-free parchment paper soaked in light machine oil between the surfaces. That way the surfaces will not rust and (perhaps more importantly) the finely milled flat surfaces will never cold-weld together.[1] Similar considerations apply to your Gauge Blocks, don’t let them touch each other, handle them with clean cloth shop gloves, store them in a box with dry dessicant packets.[2]
Liability: For quick measurements, ignore these rules and just whip out your five dollar Harbor Freight digital calipers from China. I am perfectly fine with that. When precision and traceability matter, use best practices and document it in a perpetual Engineering or Laboratory Notebook. Documenting what you do as a professional is critical. Once you turn-over the product of your work to the end-user, you have zero assurance what you made will be handled properly. If it fails, at-least you have proof of your quality of work, and when the product was turned over. Sign and date everything. In many countries a unique QA stamp (Chop) will be required as well.
1. Cold Welding
https://en.wikipedia.org/wiki/Cold_welding
2. Gauge Block
https://en.wikipedia.org/wiki/Gauge_block
As it is said: tools are what separates humans from the rest of beings.
Birds say hi.
https://en.wikipedia.org/wiki/Tool_use_by_non-humans