Antenna testing Tutorial | How to use NanoVNA SAA2N Helium

Hey, what's up, Guys! Akarsh here from CETech.

Antennas are the most important of our projects. Wherever we need our projects to exhibit a distant communication, you will definitely observe an antenna to support the communication. There are a variety of antennas present in the market and we can use several different antennas for any single project of ours. But have you ever thought that how your antenna is performing? Is the low range of your device that you are observing due to the Antenna itself? Most of the time we do not give this thing much importance and most of the time the communication or range-related issues are due to the antennas themselves.

So, what to do how to check if the antenna is working fine or not. Don't worry today we are to tell you how to test your antenna performance and which antennas you can use while making projects which include LoRa and other technologies. For that, we have an SAA-2N NanoVNA with us. We also have two long and robust antennas from RAK wireless, which can be considered the best antennas for Helium miners. We will check their performance and compare them with other antennas as well and by the end of this article, you will get to learn that how you can test your own antennas.

So let's go ahead and play.

​The components used in this project can be purchased from the links mentioned below:-

SAA-2N NanoVNA: ​https://bit.ly/3sq83J6

5.8 dBi and 8 dBi Antenna: ​https://bit.ly/3iUV0fY

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What Is a VNA?

VNA stands for Vector Network Analyzer. VNAs are used to test component specifications and verify design simulations to make sure systems and their components work properly together. Today, the term “network analyzer”, is used to describe tools for a variety of “networks”. For instance, most people today have a cellular or mobile phone that runs on a 3G or 4G network. In addition, most of our homes, offices, and commercial venues all have Wi-Fi or wireless LAN “networks”. Furthermore, many computers and servers are set up in “networks” that are all linked together to the cloud. For each of these “networks”, there exists a certain network analyzer tool used to verify performance, map coverage zones, and identify problem areas.

Vector Network Analyzer performs two types of measurements – transmission and reflection. Transmission measurements pass the Vector Network Analyzer stimulus signal through the device under test, which is then measured by the Vector Network Analyzer receivers on the other side. Comparatively, reflection measurements measure the part of the VNA stimulus signal that is incident upon the Device under Test but does not pass through it.

A Vector Network Analyzer contains both a source, used to generate a known stimulus signal, and a set of receivers used to determine changes to this stimulus caused by the device-under-test or DUT. The stimulus signal is injected into the DUT and the Vector Network Analyzer measures both the signal that's reflected from the input side, as well as the signal that passes through to the output side of the DUT. The Vector Network Analyzer receivers measure the resulting signals and compare them to the known stimulus signal. The measured results are then processed by either an internal or external PC and sent to a display.

About SAA-2N NanoVNA

SAA-2N NanoVNA is a good quality VNA that is compact and comes with an inbuilt color display that is capable of showing up to 290 scan points covering up to the full low or high-frequency range. When not used as Spectrum Analyzer it can be used as Signal Generator that can generate MF/HF/VHF sinus output between 0.1MHZ-350MHz and UHF square wave output between 240MHz-960MHz. It has a built-in calibration signal generator that is used for automatic self-test and low input calibration. The NanoVNA has a MicroUSB Port as well through which it can be connected to the PC making it a PC Controlled Spectrum Analyzer. With a 3000 mah battery, It is a handy tool for component testing and antenna tuning as well. Now let's have a look at its unboxing.

The NanoVNA comes inside a cardboard box and when you open the cardboard box you will get a user manual inside, a pretty good quality small handbag carrying all the components in that, and a small control pick as well. As you open that bag you will see a pair of heavy good quality connecting wires, a micro USB cable, 3 calibration kit port connectors, and under all these things you will get your heavy and beefy NanoVNA.

The NanoVNA has two N-type Male Connector ports on the bottom side. These connector ports are bigger in comparison to the regular ports. With the ports, there are 3 small buttons on the bottom as well. These buttons are used to control the on-screen pointers and navigate to different points. On the top, there is a micro USB port through which we can charge the VNA and connect our NanoVNA to the PC as well. On the left-hand side, we have the Power ON/OFF button, and on the backside of the device, there is a sticker with the details such as model number, etc. So this was a brief description of the NanoVNA device. Now let's see how we are going to use this device.

Configuring the SAA-2N NanoVNA

Before using the NanoVNA device to test the antennas, you need to configure the device and do some calibrations and settings so that you can use the device comfortably. The steps for configuring the device are as follows:-

• First of all, Turn on the device from the button on one of the sides of the NanoVNA. As the device turns ON, you will see a Red LED turn ON on the back of the device.

• As the device turns ON, you will see a Smith Chart on the Screen. Now take the Control pick and tap it on the screen. This will open the menu on the screen and will close the menu if you tap it again. After opening the menu select the DISPLAY button and in that click on FLIP DISPLAY as that will make it easy to work with it.
• Now for starting the calibration, you need to open the menu and hit the CALIBRATE button. This will open a submenu from that you need to click the RESET button.
• Now you need to click the CALIBRATE button again. This will take you to another submenu. In that submenu, you will see three options which are OPEN, LOAD, and SHORT. These three options are the ones we need to consider. If you check the three connectors that you got with the VNA you will see these three names written on those.

• Now, Connect the Connector on which OPEN is written. and click on the OPEN button from the menu open on the screen. This will take a while and once it's done you will see a small tick in front of the name and an "O" written on the left side of the screen
• Now repeat the same process with SHORT and LOAD settings and connectors. Once these are done, click on the Done button and Save the settings in any of the slots.

• Once the settings are saved, you will see C0 written where the O, S, and L appeared. This shows that the calibration settings are done and saved successfully.

With this, the Calibration of the NanoVNA is done and it is ready to be used for testing. In the next step, you will see how to test the antennas and which antenna is better for helium miners.

Testing Process of Antennas with the NanoVNA

As you have done the calibrations in the previous step. So now you are ready to do the testing of the Antenna Part. The steps that you need to follow for testing are as given below:-

• Take an SMA to N-type connector and connect the antenna to one end of it. After connecting the Antenna, connect that to the Port of the NanoVNA.
• Now after connecting the Antenna, you need to do some settings for that you need to open the Main Menu, Click on MARKER then TRACE.
• You will see 4 Traces that were selected. Out of those 4 Traces, you need to uncheck Trace 3 and Trace 2. Now select Trace 1 and then Go back. Open the channel option and select Channel 0. This will clear the screen a bit and you will be left with a single plot on the Screen.

• Open the Menu again and click on the FORMAT button. Out of the submenu that opens, select the SWR option. This will open another graph on the Screen. From the Graph, you can get an idea of the Antenna's Performance.

• But before that, you need to set the frequency range as desired. For that, you need to open the main menu. Then click on Stimulus and from the submenu that opens up, click on the START button. This will open up a keypad using which you need to enter the Start Frequency which we will select as 300 and click on the M button which is for MHz. This will set the start frequency at 300 MHz. In the same manner, select the Stop frequency at 1000 MHz by clicking on the STOP button.

• Once the setting is done, you will see an updated curve on the screen. Now using the buttons near the ports, you need to move the marker and take the marker to the dip of the curve. After reaching the dip of the curve, you need to see the value on the top right side of the screen. This value is the SWR of the antenna. The closer that is to 1, the better is the Antenna performance and the dip present on the Curve represents the frequency at which the antenna is tuned to work or the frequency at which the antenna will perform its best.

Now as you have understood the process to test the antenna. Let's select different antennas and compare their performance.

Comparing different Antennas

​As you have done all the settings and have also learned the process of testing the antenna. Now you need to connect different antennas to the VNA and see their performances. Now let's see how my antennas performed:-

• The first antenna that I tested was a cheap Antenna marked to operate at a frequency of 433 MHz. The SWR for that antenna was fluctuating between 1.90 and 2 at a frequency of around 447 MHz which showed that the Antenna was not at all good to be used with Helium miners and all.

• The Second Antenna that I used was a Standard Antenna from RAK wireless labeled to operate in the frequency range of 863 MHz to 870 MHz. For this curve, I was not able to see the graph completely. So I changed the Start Frequency to 200 MHz which made the curve completely visible. This curve had two dips the one at a frequency of 864 MHz with an SWR of around 1.3 and the other one at 296 MHz with an SWR between 1.3 and 1.4 which showed that this antenna was slightly better.

• The Third Antenna that I used was a 5.8 dBi LoRa Fiberglass Antenna from RAK Wireless. This antenna has a length of around 80 cm rated for a frequency range of 860-930 MHz.

• The curve of this graph had a lot of dips in it which shows that the antenna can be used comfortably for a range of frequencies. But at the frequency of 868 MHz at which we want to use the antenna, the SWR was between 1.05 and 1.1 which shows that this antenna is nearly ideal and can be used for tasks such as Helium mining. This is an antenna that is recommended to use in the tasks like Helium mining. You can buy one for yourself from ​here.

• The fourth and last antenna that I tested was again from RAK wireless. It was an 8 dBi fiberglass Antenna marked to operate in the frequency range of 858-878 MHz. This antenna was longer than the previous one and the curve of this antenna was similar to the previous one but was closer to the SWR=1 line at many points.

• At the 868 MHz frequency, the SWR was again between 1.05 and 1.10. This shows that the final two antennas are the ones that are best for Applications such as Helium Miners. You can buy an 8 dBi antenna for yourself from ​here.

So in this way, we are done ​with the Antenna testing. You can repeat the same process and check the performance of the Antennas that you have. You can also test manual antennas or the ones created by you as well. With this, we bring this article to an end we will be back in a while with some new amazing projects.