Getting Started with the NanoVNA -Part 3 – PC Software

VNA Saver – PC Software

There is now a variety of PC based software that is available to use with your nanoVNA. In this post, I will be demonstrating NanoVNASaver(version 0.0.9). This is developed by Rune Broberg and is fully open source. Rune originally developed the software as a way to save Touchstone files from the NanoVNA to use in other programs, but couldn’t resist expanding it’s functionality into what is now a fairly complete PC app to run the NanoVNA. If you want to participate in conversations with Rune, He is active on the groups.io nanoVNA group which is an excellent place to find all the latest tips and experimental firmware builds etc. https://groups.io/g/nanovna-users

The software is written is compatible with Windows, Linux and Mac, but I will only show Windows in this guide.

Step 1 – Download and run software(Windows users)

Follow this link to download the latest release of NanoVNA Saver.

https://github.com/mihtjel/nanovna-saver/releases

vnaSaverDownload

For Windows you can download the pre-compiled .exe file

Once downloaded you can copy the executable to a suitable location on your computer. In m case I just dropped it onto the desktop. When you first run the application Windows will ask if you trust it. CLick the ‘Run anyway’ option and your away. Dead easy!!

Step 2 – Connect to your NanoVNA

If your NanoVNA was connected to your computer via USB before opening the software, the serial port control, may already be populated with the correct serial port number. If not, or if you have multiple serial ports you may need to find the com port number manually. You can fire up Device Manager to see a list of installed com ports.

VNASaver main screen

NanoVNA Saver. Enter the correct com port name into this box. In my case ‘COM4’

In my case the NanoVNA connected as ‘COM4’. Enter this in the serial port box and click ‘Connect to NanoVNA’. Other than the connect button being relabelled ‘Disconnect’ not a lot will happen yet.

Step 3 – Setup your sweep

Most of this is fairly self explanatory. The frequency units are Hz, which is a bit of a pain when typing large numbers.

SweepControl

Sweep Control

My top tip here is to use scientific E-notation.

So for 50KHz you can type 50e3, for 300MHz you can type 300e6. All you need to know is ‘e3’ multiplies you number by 1000 and ‘e6’ multiplies by 1,000,000.

1segment vs 10 segments

Left = 1 segment, Right = 10 segments.

Setting ‘Segments’ to greater than 1 will divide your sweep into a number of smaller 101 sample blocks. This will be at the expense of sweep time, but gets around one of the biggest drawbacks of the standard NanoVNA.

Now click ‘Sweep’ to run the VNA once. Alternatively, check the ‘Continuous sweep’ box to set automatically repeat the sweep.

Step 4 – Calibration

First disable ‘Continuous sweep’ and click the ‘Calibration’ button on the lower left of the GUI. This will bring up the calibration window. It’s worth noting that the calibration here is separate to the internal calibration of the NanoVNA so calibrations in this software will not have an effect on the nanoVNA display.

The basic calibration routine is similar to that outlined in part 1 of this blog series. The only difference is that you need to click sweep on the mainscreen before pressing each Open, Short, Load, Through and Isolation buttons.

vnasaverCAL

Calibration Window

Once all standards have been used, click apply to activate this calibration. You can also click save to store the cal for later use.

It is possible to use non-ideal standards here, so if you do happen to have an expensive cal kit that is provided with all this data, then fill your boots and add this in to get more accurate results. In theory, I could have changed my Load from 50Ω to 51Ω to compensate for my cheap load standard, but I am lazy and when measuring many things it’s not really important.

myCal

My calibration. With Load connected to port 1.

Changing your display.

For my next blog post, I want to measure one of my Ultra-Wideband Spiral Antennas. For this, I am only interested in S11 measurements for the time being, but it would be nice to show SWR also.

Click ‘Display Setup …’

Display setup

Display setup

I will choose VSWR for the lower left plot.

SPI300 S11

HexAndFlex 300MHZ+ Circularly Polarised Spiral Antenna.

Now lets have a quick look at how this compares to a professional grade VNA. I initially tried using the NanoVNA saver to import a Touchstone S2P file from a proffesional grade VNA, but i didn’t trust the results, so I used QUCSstudio to import them both.

QUCSnanoVNAcompare

Using QUCS studio to compare touchstone files

Top Tip – QUCS studio can read your touchstone files and make them part of an electronic simulation. It can also automatically calculate a matching network for any given frequency.

nanoVNAcompare

QUCStudio comparison

This was a quick test and I really didn’t take too much care to isolate the cable from the antenna. At lower frequencies(below the 300MHz design frequency) the cable is not as well isolated from the antenna. To make better measurements of this I would want to add a balun, or some ferrites to the cable to help isolate the DUT(Device Under Test) from the cable.

Conclusion

VNASaver is a great tool. Much better than the basic software that was originally available for the NanoVNA. The author, Rune is regularly updating it with new features and UI improvements. I will need to do further work to fully explore its features, but for now I can highly recommend it.

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Getting Started with the NanoVNA -part 2

In the previous post, we got up to speed with the basics of what a VNA is and how to run a basic calibration. In this post we will look at configuring the traces and formats.

Note on Charging – One note, before we go deeper. My NanoVNA doesno like to charge from my PC USB type C port or my Samsung Quick charger. Use a regular USB-Type-A from an less intelligent charger and it’s fine.

Configuring Traces, Channels and Formats.

Throughout this guide, I will assume you are using a stylus(or your finger) to control the NanoVNA via the touchscreen. You can of course use the rocker control to perform all these applications. Read more ›

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Getting Started with the NanoVNA -part 1

This post now includes some edits based on user feedback[in green italic]

What is a VNA?

The Vector Network Analyser is an essential piece of test equipment that no RF engineer should be without. If you have previously worked with Electronics at low frequencies, you may consider a good DMM or Oscilloscope your best friend. RF Engineers would gladly trade both a scope for a good VNA!

A good VNA is an expensive bit of kit. Many years ago, a good one would probably cost you as much as a fairly nice house. Nowadays, you can pickup something really good for the price of a nice car. Note, High-end VNAs can still sell for between $100K and $1M. I will use the term ‘professional VNA’.

carorVNA

“What’s it’s dynamic range again?”

Read more ›

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Spiral Antenna – Part 3 – Results and Suckers

In the chamber

Antenna in Test Lab

The original aim for this antenna was to be a general purpose antenna that worked down to 400MHz. The results are now in and I am really pleased with them. The antenna was tested by AntennaTestLab in a full anechoic chamber with a 3D positioning system to automatically rotate the antenna. ATL use a dual polarized (horizonal and vertical) Vivaldi antenna to measure the radiation pattern. By recording both the amplitude and phase of each antenna they can use clever math to calculate the circular polarized gain. Clever stuff eh?! Take a look at ATL’s writeup here

Read more ›

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Spiral Antenna – Part 2 – Modelling and Simulation with OpenEMS

Now tested by AntennaTestLab. For now see results here

Electromagnetic simulation software can be very expensive. While some software is cheaper, it often comes with either technical or artificial limitations. There are however a couple of free alternatives.

NEC2 – Originally written by Lawrence Livermore National Labs, NEC2 was open sourced many years ago. Since then a couple of users have created good free or low cost front ends for it. 4NEC2 is my personal favourite. The best feature is it’s speed, especially if you can find a copy of NEC2/MP that makes good use of multiple core moderns processors. The big limitation is with dielectrics. Everything in NEC2 is either wire, free-space or earth.

OpenEMS – A Finite Difference Time Domain (FDTD) tool that uses MATLAB or the excellent free Octave as a front end. It was created by Thortsten Liebig at the General and Theoretical Engineering University in Germany. As suggested in FDTD, OpenEMS uses a time-domain approximation of Maxwells equations to calculate the results. The big advantage of OpenEMS over NEC2 is that it can handle bulk dielectric materials with different EM properties, I will need this to simulate an antenna on FR4 with an Er~=4. While it may not seem it at first, being able to generate geometry mathematically in is another advantage. This is especially true for a spiral antenna. Hence this is the package I decided to learn and use for this project.

Dont Panic!!!

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Spiral Antenna – Part 1

Why?

My original Palm Tree Vivaldi Antenna has proved amazingly popular. Much more so than I originally intended. The design aim for this was primarily for it to be small and portable.

When deciding what to do next I decided to create a survey and see what other people were interested in.

Survey

R&D Survey Results

The overwhelming response was that people wanted a bigger version that would cover lower frequencies. I can understand this, there are loads of interesting signals below 800MHz.

Read more ›

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Reconfigurable Ultra-Wideband Antenna Array Kit – part 2 (Spacing)

Why Spacing Matters

Firstly, the antenna array I am designing is a fixed in-phase array. Hence we assume that the total path length from each antenna to the single input/output connection are the same length. This makes the design and analysis much simpler, especially for an ultra-wide-band design.

In my design signals that arrive at right angle to the antenna will add up co-herently (in-phase)

spacing boresight

Signals arriving from boresight add up in phase

Read more ›

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