NANOVna-Saver | George Cox

USING NANOVNA-SAVER

If you have a NanoVNA, do yourself a favor and download NanoVNA-Saver. It's free and makes using a Nano so much easier. It's more flexible and has lots of nice enhancements. There is no documentation that I have found, so here are a few tips that I found using the software:

Getting started:

When you run NanoVNA-Saver you will see a black “DOS” styled window with python error trace messages, and a white, windows style window where you will interact with the app.

First, you will need to connect to your NanoVNA V2 to a USB port on your computer. Click Rescan and a comm port should show in the port combo box. Click Connect to device, and the button should change to Disconnect.

Next, you will need a calibration in order to use the app. I made one calibration file to cover all the HF ham bands that I use. I named the file frequency range and by the cable I used to connect to the device under test. I have a “close” calibration file, a 6 ft and a 50 ft cable calibration file.

Make a calibration:

In order to make a calibration, you will need to do two things:

Set the sweep settings for the calibration band.
Use the Calibration assistant to actually do the calibration.

After the calibration is done, be sure to save the file with a name that you will recognize next time you need to work in this band.

Setting the sweep:

Click “Sweep Settings”

1. Select the desired band with the “Select Band” combo.
2. Select 100% for Band Pad.
3. Select either “Single Sweep” or “Averaged Sweep”. I recommend using Averaged, but it will take 3 times longer to do the calibration.
4. Be sure to click on the “Set Band Sweep” button. This will set the sweep values in the Sweep control value boxes on the main page. You can now close the Sweep Settings dialog window.
Increase the number of “Segments” until the value for Hz/step is below 100 Hz, I prefer around 50 Hz.

Using “Calibration Assistant”

Set the Sweep for the calibration: For the HF ham bands, I made a calibration file for 1 to 30 MHz, using 3 reading average and 100 segments. This yields a file with a calibration point every 3KHz, plenty close enough for my use. Now I can just load this calibration file and work on any HF band without worrying if I have the right calibration file loaded!
Click the “Calibration” button on the main form. This will bring up the Calibration Dialog form
Click the “Calibration Assistant” button
This will bring up a series of instructional messages to guide you through the calibration process. You can stop after the “Load” calibration step, if you will never attach anything to the S21 port, else, you should do the patch cable step.
After you have finished the “Calibration Assistant” process. BE SURE TO “Save Calibration”!

Making a measurement:

Set the sweep and Load Calibration:

Follow the same procedure used in Calibration: “Setting the Sweep” You can choose “Continuous Sweep” if appropriate. Click “Set Band Sweep” and close the Sweep Settings Dialog. You can then change the “Span” and “Center” values if you want to look at a specific part of a band.
Click “Calibration…” button. Click “Load Calibration” button, and select and load the correct calibration file you created in the “Make a Calibration” procedure. Make sure the file named appears under the “Active Calibration” section at the top left of the dialog. Close the Calibration dialog.

Run the Measurement:

Click the “Sweep” Button. When the progress bar shows 100%. you can then review the results of your measurement.

The Markers:

I have 3 markers setup: #1 for 2.0 SWR at low frequency crossing, #2 for 2.0 SWR at high frequency crossing, and #3 for lowest SWR frequency. I have “Delta Marker” checked, and it shows the frequency difference between marker #2 minus marker #1. Since these markers are at the 2.0 SWR points, this value is the -3 db bandwidth of the antenna at the marker #3 center frequency.

Setup and format a marker:

Click “Display Setup”. This brings up a Dialog that allows control of most of the Main window display. At the bottom are the “Add” and “Remove” buttons for markers. Add markers as needed.
Just above the “Displayed Charts” section are the marker appearance controls. I have them set to: Show Marker Numbers, Line and Points = 2px, Marker = 10px, Filled Markers checked, Data point at tip of the Marker.
NOTE: there is a bug in version 0.4.0 that the marker triangle will not display until you change the Marker Size value. This problem will also occur when you restart the App.
To the right of the Marker settings is a VSWR section. The App defaults to a 2.o Marker, I also added a 3.0 marker.
After the “Display Settings” are complete, close the dialog.

Using the Markers:

After a sweep run, Click to enable Marker 1. Look at the VSWR chart. Find the point where the trace touches the 2.0 VSWR line on the low frequency side and clink there. This will place #1 marker on 2.0 SWR. Click to enable Marker 2. Click where the trace touches the 2.0 VSWR line on the high frequency side, to place marker 2 there. If you have “Enable Delta Marker” checked, you can read the bandwidth on Delta Marker (Click “Show Data” the see the data associated with the markers.)

NOTE: you can use the keyboard up down arrow keys to fine adjuster the marker position to the closest point on the trace to the 2.0 line. This is only available after you click on the chart to plaice a marker. This will step through the saved scan readings. These readings are not necessarily monotonic due to noise during the scan. This will be most apparent if you did not select 3 point average in scan setting.
Click to enable Marker 3. You can place it on the chart just like the other markers, or set it to the minimum VSWR frequency shown below Delta Marker. You will then be able to read the Impedance and phase and other info about the antenna on the Marker 3 data display.

Hints and Techniques:

SWR Adjustment:

If I'm making several measurements on the same frequency to adjust the SWR, I set that frequency in the "Center" frequency box, set the "Span" to 100KHz, and the segments to 40. This gives 25Hz/step resolution but doesn't take forever to run!

On startup and after a Crash:

Connect to device, you will need to reconnect after a crash!
There is a bug in version 0.4.0 that the marker triangle will not display until you change the Marker Size value. This problem will also occur when you restart the App.
Re-load your calibration file.
Re-check "Enable Delta Marker" if you are using it.
Reset your Sweep Settings