Nano Vector Network Analyser (NanoVNA)

Introduction

The NanoVNA is a compact, handheld Vector Network Analyser (VNA) originally developed by edy555. Despite its affordable price, it delivers impressive performance, making it a popular choice among HAM Operators. Equipped with an LCD display and powered by a 3.7V Li-ion battery, the NanoVNA has become a staple tool for Radio Freqiency (RF) and antenna analysis since its first introduction in 2019. The VNA output is reflected in S-parameters which provide a framework for describing networks based on the ratio of incident and reflected microwaves.

• S11 measures how much of a wave is reflected in the transmission channel (Input reflected wave/Input incident wave
• S21 measures the insertion loss (Output Reflected wave/Input incident wave)

The figure above shows the NanoVNA unit plus its accessories. The plugs are used as part of the callibration process.

• Extender cable (Male to Male)
• Through (Female to Female)
• Open circuit plug
• Short circuit plug
• 50Ω Load plug

Set the frequency range

Click on the centre of the screen and a menu appears on the right side. Set the frequency range for test, for example the 2m band.

• Click for menu STIMULUS
• START >> Select Frequency, say 144M
• STOP >> Select Frequency, say 146M

Calibrate the device

Click on the centre of the screen and a menu appears on the right side. Set the frequency range for test, for example the 2m band.

• Click BACK
• Click CALIBRATE then RESET

Open Circuit

• Connect the Open Connector to the end of the extender cable
• Click CALIBRATE then OPEN

Short Circuit

• Connect the Short Connector to the end of the extender cable
• Click CALIBRATE >> SHORT

50Ω Load

• Connect the Load Connector to the end of the extender cable
• Click CALIBRATE then LOAD

Through

• Connect the extension cable across port 1 and 2
• Click CALIBRATEthen THRU

Finish the callibration

• Click DONE

Determine the SWR of an antenna

Turn off all traces, except for Trace 0. Click on each trace until the button turn grey, except Trace 0 which should remain yellow.

Setup the display

• DISPLAY then TRACE
• DISPLAY, FORMAT S11 (REFL) then SWR
• DISPLAY, SCALE, SCALE/DIV then 0.25

Connect the Antenna to Port 1

The yellow line in the screen illustrates the SWR of the antenna, starting at 1.581 at 144 MHz and rising slightly as the frequency rises towards 146 MHz.

Test Coaxial cable

It is also possible to determine the loss over a stretch of Coaxial cable.

In this example set the frequency to the desired range. In this example 5 MHz for Start and Stop frequencies.

In this case the SWR is not required so turn off Trace 0 and enable Trace 1, the blue one. This trace is LOGMAG which displays all points on the y-axis with a logarithmic relationship

• DISPLAY then TRACE, enable Trace 1 and disable the rest

This should show a straight blue line and the loss over the cables length will be displayed in the top right of the screen. In the case of the figure -0.01 dB.