There was a time when a Vector Network Analyser or VNA was the type of instrument that cost as much as a very fancy car or even a small house. The advent of commodity semiconductors that perform at high RF frequencies coupled with microcontrollers powerful enough to handle the data acquisition and processing might not yet have put those high-perfomance instruments within reach, but at our end of the market it’s opened the possibilities for some useful yet affordable devices. A fresh contender comes from [Jankae], whose LibreVNA tops out at 6 GHz and shows some significant attention to design detail that puts it above some of the budget offerings.
At its heart is the versatile Si5351 multi-way clock generator, accompanied by a pair of MAX2871 phase-locked-loop chips for the higher frequency local oscillators. A switched bank of low-pass filters take care of local oscillator harmonics, and in the receive chain there are ADL5081 mixers feeding a dual conversion IF running at 70 MHz and then 300 kHz. Finally the ADCs are Microchip’s MCP3313, and all is kept in sync by an FPGA and an STM32G431 microcontroller. The main data proccessing is offloaded to a host computer, with a software package and GUI able to be compiled on Windows, Linux, and OSX.
The PCB shows the attention to detail, not least in the power supply arrangements, with every major component receiving its own regulator to ensure no RF makes it down the power rails. It’s clear that a properly made LibreVNA won’t be as cheap as some of its rivals, but we think the corresponding performance hike would make the extra cost worthwhile.
If VNAs are new to you, we covered an introduction from [W2AEW] a while back.
That circuit board should be made large enough for children to play cars on!
You can’t unsee it now. It almost looks like an aerial shot of a city. Neat stuff all around and hats off to the developer.
But what is Vector Network Analyser actually?
No, IWGTFY.
https://youtu.be/Sb3q8f0NBZc
VNA explained.
https://youtu.be/Sb3q8f0NBZc
Basically a signal source and a receiver that work in tandem. So you can analyze reactive circuits like filters.
The concept is simple, but to do it well required complicated and thus expensive equipment.
Useful for aligning oscillation overthrusters and flux capacitors. Also works as a dessert topping.
And a floor wax.
Hey, hey, hey, calm down, you two. New open source VNA is both a floor wax and a dessert topping!
An IOT developer’s wet dream – until now, :)
Of course there is a relevant link at the very end of the text.
Nice thing is now most of the engineers can “work at home”. ;-)
Now you just need to find a place that has Si5351 in stock. (Everywhere seems to have them “on order” at the moment. Not sure what is up.)
Semiconductor shortage all around the globe
For some reason it didn’t occur to me that it would effect these.
It affects anything made from silicon wafer
thousands listed on ebay
Wonder how many of those are genuine, not used/second source/plain fake?
It’s all well and good for high frequencies. Does anyone know of one that approaches DC for audio usage? Would be handy for seeing the transfer function of guitar amps/pedals and crossover components.
100kHz minimum. Unless your hearing is really exceptional, it probably won’t help much for audio. A better choice might be the StemLab from RedPitaya.
Nope, hearing falls off about 8 to 10 kHz. Not a bat :)
The StemLab looks interesting.
Digilents analog dicovery 2 with their BNC breakout board and their “waveforms” software might be worth having a look at.
Their impedance analyzer board coupled with the analog discovery 2 is also very usefull.
You mean like this one?
https://hackaday.io/project/164610-scalar-network-analyser
Uses an arbitrary waveform generator and 2 ‘scope channels: https://github.com/jp3141/Vector-Network-Analyzer
You could probably do that using a good quality sound card paired with Jaaa or similar software.
https://wiki.linuxaudio.org/apps/all/jaaa
Thanks all :)
I use Digilents Analog Dicovery 2 with the Impedance Analyzer Board extension. Works very good for the tasks i need it, and it’s not too expensive (considering all the other use cases the device has to offer).
It’s a closed source device and PC software tho, from what i have seen. So that is a bit of a downside for sure.
If you have a Color Computer by Radio Shack, I have an audio spectrum analyzer…
Dayton Audio has a nice little unit, DATS, that goes from 1Hz to 20KHz that does a good job of measuring the impedance and phase of speaker drivers, but it will also measure the same on cap’s and inductors; I haven’t tried a full X-over, but it would be interesting to see…
You can get it through Parts Express, a good source for anything related to speakers, drivers, X-overs, kits, and so on.
-good luck,
That is a cool effort. Would be nice to see it upgraded to a proper directional coupler and a controlled dielectric instead of fr4. Cool project although the low dynamic range will make filter work a bit spotty.
Oh, it’s for working with RF frequencies! I hope this device uses DC current and can generate FM modulated signals. I’ll have to download the PDF file using IP protocol over my LAN network to check.
Using your PC computer and viewing it on your LCD display?
I would suggest to replace power regulators from NCP702 to LP5907 series.
https://www.aliexpress.com/item/1005002428364525.html
That PCB design is gorgeous! Very cool project.
Is this a necropost at this point? Anyway… I’m happy things are being tried, but I really want something called “Libre” to be use something that we can use a 100% FLOSS toolchain with (like a Lattice.) I’m even crazy enough to wish that design tools be helpful (like KiCad instead of Altium.)
I’m not so crazy to think we’re going to be fabricating passives like resistors and capacitors in our home labs, but we have FPGAs (and therefore ASICs, eventually) and open IP cores since 2015 (?) C³ and the announcement of IceStorm… that’s a long time for people to still be using proprietary tools.
Anyway, carry on, good work. The “open” small VNA space is a warzone these days for a lot of reasons. Just want to give some money to someone who might pass it on.
LibreVNA is amazing and I very much appreciate its development. Well done to the developers
I would really love to be able to save the S-parameter data, perhaps in dB & phase format, to CSV files. This is not available as far as I can see for now, is there any possibility it will some time soon?
I’m building one as we speak! I don’t have a metal case, will try using metal paint on 3D printed plastic and see how it goes. Software looks amazing too, and it’s using QT for UI!