So, what the heck is my NanoVNA vector network analyzer? Turns out it’s a pretty useful piece of test equipment, cheap too.
You can measure performance of networks (circuits) with a VNA. It’s actually a combination of a tracking sweep generator and spectrum analyzer. Plug your RF circuit into the VNA, and you can automatically read amplitude and phase response of a signal, as well as characteristic impedance. Many hams use VNA as antenna analyzers.
Last winter, I started to hear about the NanoVNA vector network analyzer. It’s tiny and works stand-alone or connected to your PC. For US $45, I figured I could not go wrong so ordered one. It arrived quickly, but I never got around to using it until now.
Recently, I built an outboard 1.7 MHz high pass filter to reduce medium wave overload signals arriving at my wideband SDR receivers. Although I had measured its performance using my signal generator and oscilloscope, I thought taking some measurements with the NanoVNA would be a good learning experience. And it was.
Plugging in my filter as the device under test (DUT), I ran a sweep to produce the graph of insertion loss (S21 gain) as shown in the diagram above. My sweep from 500 kHz to 10 MHz showed attenuation of more than 30 dB in the AM broadcast band, followed by a flat uniform response above the cutoff frequency. Since I built my filter with lossy through-hole components on a DIY circuit board, I am very satisfied with the results.
My filter is a fifth order Elliptic type with stop-band attenuation designed at 40 dB. If I had used high-Q inductors, you would see a couple of deep notches at 770 and 1060 kHz, but even with lesser components, you can see a 35 dB notch at near this location.
NanoVNA Vector Network Analyzer – Cheap and Cheerful
My NanoVNA is easy to learn and use. It has a good LCD display and touchscreen controls. Even better is my ability to use NanoVNA Saver software. When you plug in with USB, the software gives you access to all features, including calibration. You can also create and display a wide range of graphs, like seen above.
Devices like these used to cost thousands of dollars. Obviously NanoVNA has lesser performance, but more than enough for my hobby uses.
You will also find NanoVNA a great learning tool to build your understanding of electrical circuits. Take a look at this demonstration of the NanoVNA in action measuring a filter.