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Hello builders -

I was reading some of W7ZOI’s old website entries and found one on
determining a crystal’s motional parameters by measuring the rate of change
of X (reactance) at the resonant frequency. I’ve no doubt seen this before
but how to make that measurement wasn’t readily apparent before the
nanoVNA. I’d already done a crystal characterization using the 3 dB
bandwidth technique and had good results.

The formula used with this method is

Lm = delta_X/(delta_f * 4 * PI)

I pulled out an 8 MHz EVS HC-49/W crystal which I’d previously measured
with my PHSNA system. I had done a 12 segment calibration close to 8 MHz
for my previous measurement so I applied it using nanaVNA Saver. I
connected the crystal to CH0 using a female SMA connector soldered to a
piece of PC board to which I soldered the crystal. No impedance
transformation jig required here.

I did a sweep of a few hundred Hz centered on the series resonant
frequency. The plot of X in the “S11 R + jX” plot was pretty straight.
First I picked values 100 Hz apart yielding X values of –j1.69 and +j26 for
a delta_X of 27.69 ohms. The formula gave an L value of 22 mH. This
compared pretty well with my previous PSHNA measurement of 21.54 mH. That’s
within 2%

If you know Lm, you also know Cm:

Cm = 1(4*f^2*PI^2*L) where f is the resonant frequency.

The nanoVNA will give the series resistance at resonance directly. In my
case it was 8.84 ohms versus 8.7 ohms with the PHSNA.

I thought I’d try another look with a smaller delta_f. Taking readings only
10 Hz apart I came up with Lm = 21.7 mH. That’s closer to my PHSNA value
but I won’t say with certainty that the smaller delta_f made it better. I
do think a small delta_f close to the resonant frequency is probably best.

Next I wondered if the large number of calibration points close to the
crystal frequency is necessary. So I tried a 4.9152 MHz crystal I’d
previously measured and this time used a 1.5 MHz to 10.5 MHz calibration
data set done in four segments.

I calculated an Lm value of 63.42 mH compared with 63.13 mH done previously
with PHSNA. Pretty close at 0.46%. My Rs value wasn’t as close this time:
12.26 ohms versus 10.7 ohms with PHSNA. I’m not sure of the reason for the
variation. The Rs measurement method in PHSNA is a little complicated.

So there’s another method of measuring crystal parameters with the nanoVNA.

73,

Nick, WA5BDU

I think it's this:

"Yes I have had this same problem sometimes with NanoVNA Saver. It is unpredictable when the program will crash after a calibration and the windows will all close. It probably has to do with a calculation going out of bounds.

The original developer Rune had to step back from development due to health issues and the fellow that took over did quite a few changes but seems to have stopped any further work on the program."

Is this the python application you're referring to? I've been using pieces of it and I've got the architecture pretty well figured out- my version is 13 August 2020 (V0.3.7 in the changelog.md). If someone points me to the "most recent" repo, I can see about picking up maintenance.

Folks can always try out OneOfEleven's NanoVNA-APP . It also has a calibration function built-in.
It's in the releases area:?
There is no user manual but almost all graphics menus are through the right-click on your mouse.
It can also be used to flash firmware into your Nano

Thanks. I'll probably have to do a firmware upgrade to start playing with the latest third party tools. There seems to be a lot of choice for nanoVNA firmware and I'm not sure who provides the most robust firmware upgrade for my nanoVNA-H (2.8") at the moment. There are a few niggly bugs with my existing (old!) firmware.

On Thu, Mar 18, 2021 at 06:16 PM, <nc0gnit0@...> wrote:

I can calibrate my VNA manually, but I would prefer to calibrate using Nano
Saver with my PC since the manual version does not include Isolation test.

When I have completed short, open, load, isolation and thru, I click on
"APPLY" the program disappears from my Windows 10 PC.

Yes I have had this same problem sometimes with NanoVNA Saver. It is unpredictable when the program will crash after a calibration and the windows will all close. It probably has to do with a calculation going out of bounds.

The original developer Rune had to step back from development due to health issues and the fellow that took over did quite a few changes but seems to have stopped any further work on the program.

Roger

On Fri, Mar 19, 2021 at 05:45 AM, jmr wrote:

Here's a nanoVNA-H measurement of a Micrometals T50-6 powdered iron toroid
with 22 turns spread over about 270degrees of the toroid. The inductance
should be about 2.2uH and you can see the nanoVNA does a good job again. It
also has a reasonable stab at measuring the series resistance although the
data gets a bit noisy above 20MHz. I keep meaning to add averaging to my PC
tools. The nanoVNA is much more powerful than a typical low frequency LCR
meter because it can measure the inductance across a wide frequency range. The
inductance at the design frequency can usually be measured quite accurately.
It often manages to give a reasonable estimate of Q for powdered iron toroids
like this.

If you make the measurement using the NanoVNA app by OneOfEleven you will see that it has adjustable sweep averaging and data smoothing built-in. You can also import the s1p file for post processing. The graphing capability is quite good with many scaling options. Once I starting using this tool I stopped using NanoVNA Saver. The calibration routine is very nice as well.

Roger

Kev,

You can set it to back to zero from the menu item "electrical delay". You should have received a menu map with your -H4. If you lost it try this one.... /g/nanovna-users/files/NanoVNA-H4%20Menu%20Structure%20Map_2.pdf

You will probably find the Absolute beginners Guide (files section of this group) and the wiki for this group will answer most of your questions.

Roger

"Joeqsmith" is a very knowledgeable fellow when it comes to VNAs in general and the NanoVNA in particular. He has quite a few interesting videos on his YouTube channel. His latest one is all about protecting the NanoVNA from damage from ESD and when connecting it to antennas that may have a charge on them.

He discusses gas discharge tubes and transient voltage suppressors. At the end he uses a piezo BBQ starter on the input of a NanoVNA fitted with his protection circuit.

This video is quite long but well worth watching.



Roger

Thanks in advance for any help.

I'm new to VNA's and have enjoyed reading the posts here and starting out with my H4 from Hugen.

I appear to have changed a setting and cannot find how to get rid of it - It sits top left of screen and shows as Edelay with a time in picoseconds and a negative 'm' number to the right of it.
It is throwing the Smith Chart Trace off, displaying what can only be described as an 'etch-a'sketch' type of pattern.

What have I done wrong, please?

Kev
M0TNX

On Thu, Mar 18, 2021 at 07:07 AM, WB2UAQ wrote:

Manfred, Have you ever compared the Q readings measured by the old BRC-160 or
the Hp 4342 Q meters against the Q reported by any network analyzer or even
many of the older 4 terminal instruments from the 70's and 80's and maybe into
the 90's?

There is a technique that has been described by Darko Kajfez (EE Professor Emeritus at the University of Mississippi) that actually gives good results for Hi-Q inductors on a VNA. And there is a Matlab application, available for free (if you have Matlab, I think) that implements the Kajfez technique on either an HP 8753 or HP 3577A VNA.

Some time ago, I compared the Matlab application's results with the measured Q from my HP 4342A, and (if my memory is correct) the results were surprisingly close.

If interested, I've put both the Kajfez paper and the user manual for the Matlab website on Github:
(The user manual gets into the nuts and bolts of how to actually make a measurement using this technique).

- Jeff, k6jca

Hi all,

OK, I have fixed the issue and got it working.
It appears a restart of the PC was needed, and although my nanoVNA showed up in the port area, I had to connect to it regardless.
I had tried that before, but it failed, so I gave up and performed the restart and all is now well.

Thanks for pointers and suggestions!

73 de Phil GU0SUP

Very good. Thanks. I need to update, however what I have is fine. Perhaps you can assist Phil with his issue.

Again, thanks.

No need for that anymore.

To give the nanoVNA a tougher test I tried measuring the Q of a small 50uH inductor across LF to 3MHz. In the plot below it struggles to indicate the Q as the data is very noisy and uncertain. The measurement would benefit from some averaging but it indicates a peak in the Q somewhere around 450 at about 700kHz. Clearly this inductor is at its best across 300kHz to just over 1MHz where it delivers an impressive Q factor. I think the nanoVNA is doing very well here although it would be best to measure the Q using a decent Q meter or by using the nanoVNA in a different way to measure Q.

Hello Phil,

In the past, initial cal must be made on the hardware first. Saved via default in register 0. After that, further cals can be done from the saver routine. At least that was the process using the saver at V0.2.1 version.

Alan

Hi Charlie,

When i click on that, nothing appears to happen.
It says to follow the instructions, and I get a pop-up to that says to ensure the nanoVNA is connected, which it is and shows up in the in the lower left of the main window,

73 de Phil GU0SUP

Did you perform the calibration on nanoVNA saver?

Ignacio EB4APL

--
El software de antivirus Avast ha analizado este correo electrónico en busca de virus.

Did you use the calibration assistant and follow the prompts?

On Fri, Mar 19, 2021 at 12:40 PM, Gary W9TD wrote:

Do you import the s2p from the NanoVNA then to analyze and plot?
Gary
W9TD

Yes, except in this case I'm making a 1 port s11 measurement with the nanoVNA. I use a very basic s1p data dump tool I wrote in VB and then I import the dumped s1p file into Genesys for analysis. It just takes a few seconds to do it all as I have an inductance template in Genesys for this type of analysis.