Nano VNA 2

On this web page I described how I converted an original Nano VNA sandwich board style product into something more robust, as well as describing some other useful information and resources. It did not take too long before before there were aftermarket enclosures being sold to be retro fitted  to older models.

Also the scene advanced considerably.  Advanced frequency coverage, an SD Card facility was added to save data traces, easier firmware updating via USB, a better enclosure as standard as well as additional menu additions. With regards to enhanced frequency coverage be warned that the current state of the art for these low cost devices is about 2GHz. Beyond this the measurements cannot be relied upon. So if you see units being sold with 6GHz coverage for example then forget it. The display might go there but the accuracy of the measurements will be suspect ! 

Below - Nano VNA presentation box, and generic view of the 4  inch colour display.

Usage of the VNA is the same as any other really so there is no need to repeat what has already been written by myself and others. However one useful addition is a menu item labeled LC Match.  If you are a keen experimenter, especially when it comes to building ATU's and antennas then you will probably have the tools to calculate LC values for complex impedance matching. With these latest models it's already built in ! Some owners might not even know about it.

Below is a measurement of a random wire antenna at 20 -30Mhz using the Nano VNA. You can see that at 30Mhz it's complex impedance values are 28.77 -j 211.3 Ohms. (That's minus J - J operator notation). For this example, we will assume that 30Mhz is where we want to operate. (Yeah I know it's not a ham band but that's just where the random sample took place for this experiment). Now if you look at the display you will see some options being shown. Source shunt, series shunt and load shunt values can be seen. In this example we are presented with several ways to make an ATU for it.

Let us look at the easiest one for typical use to make an L-Match. We can see it suggests having a 91pf  source shunt capacitor and a series 1.3uH inductance. Look at those values and visualise their position using the diagram below.

So, you'll have a 91pf capacitor on the left hand side from the hot end of the rig going down to ground, and a 1.5uH inductor going across at the top, which would go to the antenna.

But what are the other values that are shown ? Well they are alternative components that you could use to produce the same impedance match. Depending upon what they are then they may be practical for the user to use or not.

For example, if you only wanted to use inductors then you would see shown a 1.5uH series inductance and a load shunt inductance of 4.6uH. Once again, just look at the nomenclature diagram and place those parts in the right places and that is it. (You always ignore the unused sections, they are blank). Indeed, some impedances might not even require a two part L Match, instead there might just be a simple series inductance or a load capacitor. For the sake of clarity I have not attempted to show the last two rows of values - I think the two examples are enough.

Both examples for the real world are shown below, there's no voodoo involved, it's nice and easy.

Resources -

UK Retailer -  https://www.mirfield-electronics.co.uk/

Nano VNA group - https://groups.io/g/nanovna-users