However, SWR is only partial information and tells us nothing about the actual gain and directivity / radiation pattern of the antenna. The radiation pattern tells us in which direction the antenna receives and radiates power best from. For a Yagi, we would expect the best reception gain to come from the front, with much less gain on the sides and rear.
To set up the radiation pattern measurement, Jephthai connected the Yagi to the TX port of the NanoVNA via a long coax cable, and connected an omnidirectional whip antenna to the RX port of the NanoVNA. The NanoVNA and Yagi are separated by a reasonable distance of 18' to ensure that the far-field radiation pattern is measured instead of the near-field pattern. He then measures and collects the S21 reading over multiple rotations of the Yagi.
The data is then plotted revealing a two dimensional radiation pattern for the Yagi. As expected gain is highest in the front, and weaker on the sides and rear. Jephthai notes that the radiation pattern mostly matches what the MMANA antenna modelling software predicted too.
With the NanoVNA (and upcoming NanoVNA 2.0) being so affordable and readily available many budget focused RF enthusiasts and hams are now adding a tool to their arsenal that used to only be for the wealthy and commercial users. Vector Network Analyzers (VNAs) allow you to do things like make SWR measurements on antennas, characterize RF filters and detect coax cable faults, among other applications.
However, much like the RTL-SDR there is no one company or entity controlling the NanoVNA concept or development. The NanoVNA name now encompasses a mishmash of similar but slightly different hardware created by multiple manufacturers/community members, and multiple firmware and software developed by the community. This can be frustrating for some people as community developed products typically do not have full manuals and support that you would find in products from a larger commercial company. Instead some time to research and understand the product may be required.
Whilst almost plug and play, to use the NanoVNA you still need to understand what a VNA is, how to calibrate it, and how to read it's measurements. And in addition, for the NanoVNA in particular you'll want to know the differences in NanoVNA versions, how to update the firmware and where to find optional PC programs for it.
In order to help people new to VNAs and the NanoVNA, Christoph Schwarzler (OE1CGS) and Maximilian Schwarzler (OE1SML) have written a Kindle eBook called "A guide to the NanoVNA". The guide goes over what a VNA is and how it works, NanoVNA hardware versions and what to avoid, what accessories you might need, how to update the firmware, how to read the various charts, how to navigate the menus, how to calibrate and how to use NanoVNA PC software. The book also goes over some use cases for the NanoVNA, including creating a loading coil for a 40m short vertical antenna, creating a band pass filter, and checking for coax short circuit defects. At only US$2.99 it's a good way to get started with the NanoVNA.
Thank you to RJ Juneau (ylabrj / VA3YLB) for sharing with us his NanoVNA firmware update guide for idiots. NanoVNA firmware is updated fairly often, so this is a good reference guide for those who want to test the latest code as updating the firmware is a multi-step process. He writes
I've put together a "for idiots" document (I'm both the writer and the target audience) that holds your hand through the process of upgrading from Windows, and covers some important issues like:
Are you using a nanoVNA or an updated nanoVNA-H?
Where to pick up the right software for the board
Do you want the VNA or the antenna analyzer version?
Back in October 2019 we posted about the upcoming NanoVNA version 2.0 which back then was still being designed with a predicted release date of January 2020. Recently some photos of the NanoVNA 2.0 prototype have been uploaded to the NanoVNA groups.io forum.
The NanoVNA 2.0 is expected to retail at around US$60 which is around the same price as the current NanoVNA. The current NanoVNA is limited in that it can only measure from 50 kHz to 900 MHz, with performance being reduced above 300 MHz. It can be extended to 1.5 GHz, but with severely reduced performance. The NanoVNA 2.0 will be able to measure from 50 kHz to 3 GHz, and possibly up to 3.5 GHz. Version 2.0 will also have improved dynamic range.
The NanoVNA (v1.0) is a versatile Vector Network Analyzer (VNA) that was originally designed by @edy555 / ttrftech. What makes it so special is it's extremely low cost as it can be found on eBay & Aliexpress for under US$40 and on Amazon for around US$50-US$70. A VNA is an extremely useful tool in any ham or RF enthusiasts tool belt as it can be used to measure RF filters, tune antennas, measure coax cable loss, and find cable faults.
NanoVNA Version, Model, Naming and Credit Confusion
Eddy555's original NanoVNA design has already been released for several years prior to the current NanoVNA popularity boom, but during those years eddy555 was only selling the product in small quantities as a DIY kitset.
The current low cost NanoVNA's available on the market now are mostly the "hugen" version known as the NanoVNA-H. Hugen is a ham who innovated on eddy555's original open source design, adding features like battery management, improved PCB layout, PC software and extending the frequency range from 300 MHz to 900 MHz.
There is now also the "NanoVNA-F" version available which is a clone of the "NanoVNA-H" but with a larger 4.3" screen, larger battery, range extended to 1 GHz, and firmware based on a RToS. It sells at a much higher price of US$110 - US$129.
Finally, we note that the NanoVNA 2.0 project described in the first part of this post does not appear to be affiliated with eddy555 or hugen in any way. Development of the NanoVNA 2.0 is apparently based on completely original design work, and only shares similarity to the original NanoVNA in terms of pricing, name, and firmware compatibility. NanoVNA 2.0 is being developed by OwOComm which is a Japanese research unit that aims to promote "intellectual communism".
OwOComm note that they will release the designs as open source without actually manufacturing the product. It's then up to any factory to manufacture and sell the design as they please. OwOComm themselves appear to be sponsored by an unnamed customer of theirs who wanted an "improved NanoVNA" to be designed. It's not clear what the goals of OwOComm or their unnamed sponsor is, other than perhaps philanthropic.
At the same time we note that eddy555 appears to be designing his own NanoVNA 2.0 version which is not affiliated with the NanoVNA 2.0 described in this post. In the forum thread eddy555 has urged OwOComm to rename their project to avoid confusion, but it is unclear if they will do so.
The story of an open source project running away from the original developer seems to be a fairly common one these days. While eddy555's original open source design has started something truly great, it is at the same time sad that he won't see much credit or profit from future designs.
Previously we've been posting about the NanoVNA which is an open source VNA project by @edy555 / ttrftech that has recently become extremely affordable at less than US$50 for a fully assembled unit thanks to Chinese manufacturing (or a little more if you order it via Amazon).
Over on the NanoVNA groups.io forums we've seen discussion about a NanoVNA hardware version 2.0 being in the works and it could be ready as soon as January 2020.
The nanoVNA [v2] will eventually reach 3GHz (and at a similar price to version 1).
It's going to be based on the adf4350 + si5351.
The 3 mixers are replaced with one higher spec mixer (ad8342) that is switched between the 3 channels.
A variable gain amplifier is added at baseband using one opamp and switched feedback resistors for improved dynamic range.
The Audio codec is removed and the stm32 built in ADC is used instead.
The performance should be comparable or better to V1.
Info about the baseband VGA design: A RFIC switch is used to switch the shunt resistor in the feedback path. The switch is basically "transparent" because the off state capacitance is in the femtofarad range (it is an RF switch) which is negligible at the IF frequency. The on state resistance is small compared to the resistors being switched in. Since the amplifier gain is mainly dictated by the feedback network, and the switch is "transparent", there is nothing other than the tempco of the physical resistors that can cause a temperature dependence. The RFIC used is the same as for the receiver RF switch, and it turns out all the maxscend switches do not have the shunt diode problem (most RF switch ICs have parasitic diodes from RF input to ground which will start to conduct at lower frequencies), so it has no theoretical lower frequency limit and can be applied at the IF frequency. This is a big improvement over using normal analog switch ICs which have capacitance in the pF range.
Info about linearity: The code will perform a calibration of each VGA step on boot up. Since there is no temperature dependence the calibration only needs to happen once.
The layout designer has also posted, noting that the price will remain the same (roughly $50), but there will be several improvements including a wider frequency range, better dynamic range, and an improved PC interface.
Hi, NanoVNA V2 layout designer here. Here is what I know:
V2 won't have a bigger display because it is too expensive
frequency range will go to at least 3.5GHz; PLL limit is 4.4GHz.
ADF4350 is used because of cost reasons; ADF4351 is more expensive by a factor of 5.
The layout is already fairly packed, so modular is not possible without a huge form factor.
Layout and shielding are much improved for higher dynamic range.
Price will be around the same as the existing NanoVNA. The design is already cost limited, so we can not do anything that will further add cost.
PC interface will be completely reworked. A binary protocol will be used similar to the xaVNA (we are going for full compatibility with the xaVNA PC software). If you are writing custom PC software for the Nano, please make sure the USB interfacing part is well abstracted away and easy to change.
The development timeline is going to be pretty long (by Chinese standards at least). We will iterate on PCB layout to get the best dynamic range. I think we might see initial (quantity limited) sales in ~3 months.
Just as a footnote, we received several emails from readers who wanted to make sure we note the credit edy555 should get. Originally edy555 had planned to produce his own units, but due to a Chinese ham enthusiast who had good intentions the design became popular and was soon cloned. We note that the NanoVNA v2.0 does not appear to be affiliated with edy555.
The NanoVNA is an open source VNA project by @edy555 and ttrftech that has recently become extremely affordable at less than US$50 for a fully assembled unit thanks to Chinese manufacturing (or a little more if you order it via Amazon).
Ohan Smit had recently been playing with the NanoVNA and came across a software package from Rune B. Broberg (5Q5R) called NanoVNASaver. NanoVNASaver is an open source program that can be used to read and plot data from the NanoVNA. It has some nice features like the ability to display multiple charts, increase the resolution up to 10k points, measure cable length via TDR calculations, save Touchstone files and more.
Later in the same post Ohan also includes an update about his experiments with some new experimental NanoVNA firmware that extends the maximum frequency range from the previous maximum of 900 MHz up to 1500 MHz. Results show that while it can work up to 1500 MHz, accuracy rapidly degrades above 900 MHz.
As the NanoVNA project is open source the code is ever evolving and the units that ship from China now come with older firmware installed. If you want to test the very latest experimental code, you need to compile it on a PC, and then flash the firmware into the NanoVNA. Ohan's guide covers this all. For example, one recent update now enables time-domain reflectometry for measuring coax cable length, which we explored in a previous post.
Alternatively according to the GitHub readme, it is also possible to use a docker image which will remove the need to install the arm tool chain. Ready to flash images are also released every few days over on the GitHub release page, although these won't include the very latest or experimental changes.
Earlier in the month we posted about the NanoVNA, an open source VNA project by @edy555 and ttrftech that has recently become extremely affordable at US$50 for a fully assembled unit thanks to Chinese manufacturing.
Nucclearrambo provides a Python script which can be used with the NanoVNA's S1P output data to create a TDR graph. His tests with RG405 and LMR200 cable show that the length reported by the script comes remarkably close to the actual length.