20/12/2019

ON7DQ NanoVNA Presentation




On December 20, 2019, I gave a presentation on the theory and practice of using a NanoVNA, mainly targeted at hams and homebrewers in the Ostend radio club.

The presentation was in Dutch, and has been recorded on video for YouTube.
The slides have also been translated in English.
all material is free to view or download, links are at the end of this post.

Over 50 people attended, our new club house was really full, and some people even came from far-away clubs to hear my talk ... quite a succes !
Here some pictures of the public ... and yours truly in action.





They certainly got a lot of stuff to digest, the presentation lasted over 4 hours, we started at 20:00 local time, and ended well past midnight ;-)
In the middle we had a break of course, everyone, inlcuding myself, needed a drink !

Part 1 was all the theory you can't live without : complex impedance and admittance, transmission lines, reflection coefficient, return loss, SWR , S-parameters, and of course a basic understanding of the Smith Chart.



Part 2 was all about scalar and vectorial network analyzers, how to calibrate and measure, and also using the excellent NanoVNA Saver program (link here )

Of course we discussed the measurement of classical one-port  (antennas !) and two-port devices (filters !) first.

Everything was shown with some practical examples, using little circuit boards that I prepared, e.g. here a complex load with R and C on the little board to the left, that was then matched with an L/C network (the board to the right). The "matching board" can house several L- or PI-configurations, I got the idea from a W2AEW video on YouTube (this one).



A simple 40m Low-Pass Filter was also built in the same way.



Some extra features were the use in TDR mode, to determine the distance to a fault on the cable, or just to measure its length, and determine the characterisitic impedance.

For the application as a "component tester" , I made a small component adapter, see picture below.
2 pins of a 4-pin female header are connected to ground, the other 2 to the center pin of a male SMA connector.
On a row of jumper pins, I made a SHORT, an OPEN and a 49.9 Ohm SMD resistor, as a quick and simple calibration set.
When the CAL set is unplugged, most wired components can be plugged in, and for measuring SMD's , I bent out the middle prongs, just hold the SMD component against the prongs to measure it.



Finally, the NanoVNA can also be used as a simple signal generator, and with some caution, even as a very basic spectrum monitor (I wouldn't call it a spectrum analyzer though).

Reference materials :

Links to the videos on YouTube (in Dutch)
Part 1 : Theory
Part 2 : Practice

Slides in Dutch are here
Slides in English are here

Enjoy !

Luc ON7DQ

3 comments:

  1. Hi Luc,
    I've been going throuigh your NanoVNA presentation and it's been very helpful. However, I was having trouble repeating your results with the 40m low pass filter. The problem seems to be you have used 40m values for the capacitors, but 30m values for the inductors.

    Thanks for the presentation. I'm not new to electronics (ham for 62 years), but new to VNA's so this was a great jumpstart for me.

    Eric KE6US

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  2. Well have you ever ... indeed I did use the wrong inductors !
    It was all done in a hurry ... and since it was just for the demo, nobody noticed it so far, the filter does look like a LPF doesn't it ? HI.
    Thanks for finding that error, I'll correct the presentation, AND my filter asap.
    73 , Luc ON7DQ

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    Replies
    1. I had an advantage. I made a set of those filters a couple years ago that I use on the bench. I already knew the characteristics and roughly remembered the values. Your demo filter DOES work as a LP, but the cut-off is extended a couple of MHz.

      Thanks again for a very useful tutorial on the NanoVNA.
      Eric KE6US

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