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I've been thinking about a test jig for measuring capacitors and inductors.

Ideally, this would have built in calibration modes and support all
three DUT measurement configurations with the VNA.

On Wed, Oct 16, 2019 at 5:57 AM Starsekr via Groups.Io
<Starsekr@...> wrote:

Can't see why it is off topic. Much of the calibration is about test jigs or extensions of the reference plane. See hash tag #test-jigs. BTW, hashtags are active in this group. BUT they can only be created by a person starting a topic. There are several links in the wiki to practical uses of the VNA, many have test jig examples. Look under other VNA and related links. Issues with jigs are often calibration and error reduction.

Hi Sala,

Some test jig ideas can be found here:

I found if leads are pushed into the breadboard hard enough, they will short to foil. Better to flip single sided PWB. Breadboard from Mouser. PWB blank from Amazon.

John KN5L

"I measured a simple class A common emitter amplifier and theory and test results do not match."

Beware of signal levels, especially when measuring active devices.

Regards,

Martin - G8JNJ

On Tue, Oct 15, 2019 at 11:58 PM, Starsekr wrote:

Saw this on eBay.

I ordered these to hack:

By the time you get the boards made and get the connectors, you have spent at least as much as Marcus is asking.
He has done the research and gotten the line section correct for the board material.

Glenn

--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

If I could get past this driver problem then I think the rest would fall into place.

The windows operating system needs an STMicroelectronics driver installed.

'DfuSeDemo.exe' installed for me in a folder that also includes a 'Driver' folder,
in which are folders for Win7-10, in each of which are subfolders for x64 and x86 (AKA 32-bit).
In each of those driver subfolders is an installer .exe
Run >>only<< the one that matches your Windows version and bit-depth.

Alternatively:
* right-click on "My PC" icon, select 'Properties'
* select 'Device Manager'
* attach and turn on nanoVNA, open:
> Ports (COM & LPT)
* select the appropriate COM port
- if you do not know which one, simply turn nanoVNA off/on to see which disappears and reappears
* right-click and select "Update Driver Software..."
* browse that back to the DfuSeDemo.exe installation folder

Can't see why it is off topic. Much of the calibration is about test jigs or extensions of the reference plane. See hash tag #test-jigs. BTW, hashtags are active in this group. BUT they can only be created by a person starting a topic. There are several links in the wiki to practical uses of the VNA, many have test jig examples. Look under other VNA and related links. Issues with jigs are often calibration and error reduction.

I measured a simple class A common emitter amplifier and theory and test results do not match.

So, it will be fun and interesting to measure some amplifiers. Have you ideas for test jigs What to include, where to buy and so on. (And what forum to use, because I think this is a bit OFF-TOPIC here).
I think I need to have card edge SMA connectors, SOT23, SOT89 and SOT143 pads, what else? Inductors have to be tested also. I can make my own PCB, but I can some also.

There is a how-to, linked in Wiki Application Notes:

I like it the fact that I can use it non-interactively.

Non-interactively, after downloading the four *.p files from above:
* One time only, to generate gridpoint data file `smithgrid.dat`, run:

C:\Users\ormpoa>gnuplot smithgrid.p

* modify plotsmith.p to generate Smith charts from wanted Touchstone files,
adding rectangular plots e.g. per

C:\Users\ormpoa>gnuplot plotsmith.p

being able to generate all the PDF plots from a single unix shell script
makes the process much easier.

* .. so you already know how in a gnuplot script to generate PDF, e.g.

set term push
set term pdfcairo
set output 'YourFilename.pdf'
replot
set term pop

Hello Gyula
I also have Rune's fantastic application running on a 32 bit Windows7 machine but battled to get running on a 32bit version of Ubunu (latest LTS v18) and after a remote session with Ohan (ZS1SCI - a VERY knowledgeable software developer), established that not possible on a 32 bit Linux machine as per note from Rune.

I wish you a great time using the nanovna + nanovna-saver, LOTS to experiment with for sure!

73

Nigel ZS6RN ex G8DEV

Hi Gyula,
you're right, the software works fine without 64 bit hardware. The
downloadable executable from GitHub also works with Windows 7 32 bit.

However, PyQt5 is not available from pip for 32 bit Linux, so any 32 bit
Linux users would have to install and compile this manually.

--
Rune / 5Q5R

Hi,

I have Python 3.7.4 installed on win7-32 bit SP1 integrated, which runs the nanovna saver.
Of course, the required modules are installed with the -pip command, and I have verified that they are present. I don't think 64-bit hardware is needed to get it running.

73, Gyula HA3HZ

Hi Bryan,
thank you very much! :D

I'll sit down this evening and read through your explanation more
thoroughly than this morning's coffee break allows. But I will comment
briefly on the crashes: If you want, it would be helpful for me if you were
to launch the application from a command prompt (or terminal window if on
Linux), preferably using the "-d" parameter to enable debugging output.
After the crash, the final error message should then be preserved in that
window. This will show me exactly where in the code the crash occurred.

When it comes to calibration, I have a decent idea. It won't be fixed in
0.1.3, due out Soon<tm>, but I promise I'll make better input validation
for those fields for 0.1.4 ;-) For now: Never leave them empty, never set
C0 to 0, and never feed them after midnight.

PS. I swapped F and H in the calibration window, and *noone noticed* until
now?! Quite how I made that mistake I don't know. :-)
--
Rune / 5Q5R

On Wed, 16 Oct 2019 at 07:10, bryburns via Groups.Io <bryburns=
[email protected]> wrote:

On Tue, Oct 15, 2019 at 03:42 PM, Rune Broberg wrote:

This looks very interesting, Bryan! I am happy that my little piece of
software has turned out to be able to do things like this ;-)

I am a little curious to see Smith chart measurements of your open, load
and short after doing this calibration adjustment - just to see how much

it

changes how they look.

I have wondered a little whether allowing a pure resistive value for the
short would also be relevant?

I'm still looking for a good reference for the calculations for how to
compensate for a "load" standard that has a capacitive component: How

does

that look? Is it just like the inductive phase shift with the sign
reversed? Could a load capacitance reasonably be represented by a

negative

inductance?
--
Rune / 5Q5R

Rune,

Yes, your software can do a lot of things that I seem to need. Thanks,
again, for continuing to work on this effort. You and your efforts are
greatly appreciated.

I will cover the changes in the open, short, and load separately below.
To get the plots shown here, I averaged 3 (or more) copies of 5 scans from
50 kHz to 900 MHz. The total number of frequency samples was therefore 505
samples or about every 1.78 MHz. Averaging is very useful and important in
nanoVNASaver, especially when looking at these kinds of measurements,
especially above 300 MHz.

First I'll talk about the open.

On the Smith chart plot little change is observable after the tuning is
applied because the changes being made represent small changes in the phase
of S11. In fact, to see the changes one has to look at the phase of S11 on
a scale of about +/- 2 degrees. The S11 phase of the open is shown in the
file "S11-Open-Phase-NoTuning.png". The change is such a small change in
the phase, it is almost impossible to see anything on the Smith chart. The
data is all clustered near the right side of the Smith Chart as it should
be after an effective calibration. However, it appears to me there is real
data in this phase plot, even after calibration but before applying any
tuning to the parameters in the "Calibration standards" form. When I
changed C0 in the "Calibration standards" form of nanoVNA-Saver to 1200 and
the offset delay to -55 ps. This change produced the phase plot in the
file "S11-Open-Phase-with-Tuning.png". Notice two things about the plot
after tuning. 1) There is no "quadratic looking" drop in the phase as we
move from low frequencies to higher frequencies as there was before
tuning. 2) Although I did not do this, a linear fit to the data in the
phase plot after tuning will be a horizontal line near zero degrees. This
is the definition of an ideal open. Thus, while you cannot readily see
such a small change on a Smith chart, there is some significance to the
changes because we removed frequency dependent artifacts of the open I used
in the calibration process. Please also notice from the amplitude charts
in the first post in this series show some improvement in the trend of S11
in dB when measuring the open RG-213 cable. This is not very compelling,
but read on.

Now let's talk about the short.

The short I used produced a nice dot on the left side of the Smith Chart
after the normal calibration; however, there was significant ripple
remaining in the S11 amplitude as shown in the plot below
"RG-213-WithOpenOnlyTuning.png" I suspected, but did not know that could
be the fault of the inductance in the short that was used in the
calibration. By modifying the L0 parameter in the "Calibrations standards"
form we can remove the inductance that may be present in the short I used.
The resulting S11 amplitude plot is attached to the first post above and
called "S11-RG213-WithCalTuning.png". Also, please refer to my post to
Kurt in this thread that shows the vastly improved Smith chart for the
RG-213 cable. The circles are now circles and they are much more closely
centered on 50 ohms.

So, now to your question: What does the actual short used in the original
calibration look like on the Smith chart once the L0 correction for the
Short is inserted? The result is shown in the figure
"Smith-OriginalShort-WithCorrections.png". This result should be exactly
like a 1.2 nH inductor which is what I tried to remove using the L0 term.
In fact, nanoVNA-Saver confirms this inductance after this correction is
applied by indicating 1.2 nH is the "parallel X" when measuring the actual
short. When the VNA is properly calibrated for a short, it shows the
actual inductance of the physical device I used, equivalent to 1.2 nH.

In the case of my BNC short, I don't think I have the ability to reliably
measure a resistance that small. The ohmmeter I have won't go lower than
0.05 ohms even when shorting the test leads together. When measuring the
short I used, it still measures 0.05 ohms. I doubt that many folks doing
hobbyist work can measure the resistance of their short either. Such small
resistance values have little impact in a 50 ohm system. Therefore, I don't
think there is benefit to including a resistor as a part of the cal
correction for a short.

A discussion of the load follows.

I won't go into the details about the tuning I did for the load. A
similar procedure to what was used for the open was used for the load.
Here, again, averaging a lot of sweeps is important in order to measure the
trends in the phase of a signal with a return loss of some 40 to 50 dB.
In order to flatten the S11 phase of the termination I used for calibration
I did need to add a very small amount of inductance (50 e-12) in the
calibration form. This is the equivalent of trying to remove 0.05 nH, a
small amount indeed. At 900 MHz that is a reactance of about 0.28 ohms.
Certainly not huge in a 50 ohm system. Of course, this small change is
unobservable on a Smith chart using the nanoVNA but it is clearly visible
on the S11 phase plot.

Long papers have been written on all of the possible issues with trying to
model various loads and what to do to compensate for various types of loads
at various frequencies. I think there are too many topologies to deal with
in this type of software. The capacitance can be in series with the 50 ohm
resistor or it can be in parallel or there might be capacitance in series
and in parallel.... The same can be said of the inductance. In my
opinion, you could leave what you have in place and let folks work with it
so long as you allow negative numbers everywhere. Then folks can think
about things in whatever way they must as long as you are clear about what
you are doing in the software with the non-ideal values entered in the
various boxes of the "Calibration standards" box.

By-the-way - When I reset some of the values in the Calibration standards
box to zero after putting in and applying values, nanoVNA-Saver 0.1.2
immediately crashes. You might want to look into this. I am sure it is
reproducible. Right now, I don't recall which ones do it.

I hope this helps answer your questions.

Again, thank you Rune for making the nanoVNA-Saver software available. I
find it particularly valuable and useful.

--
Bryan, WA5VAH

On Tue, Oct 15, 2019 at 03:59 PM, Dr. David Kirkby from Kirkby Microwave Ltd wrote:

I suspect it uses
just one mixer and one receiver, which is what all simple VNAs do to keep
the cost down

The nanoVNA is a full three mixer three receiver VNA without the switch to reverse the signal path

Hi Paul,
great to hear that it runs on Fedora :D Thanks for trying out the software,
and for helping other users get it running as well!

--
Rune / 5Q5R

On Wed, 16 Oct 2019 at 06:10, bryburns via Groups.Io <bryburns=
[email protected]> wrote:

On Tue, Oct 15, 2019 at 03:42 PM, Rune Broberg wrote:.

In the case of my BNC short, I don't think I have the ability to reliably
measure a resistance that small. The ohmmeter I have won't go lower than
0.05 ohms even when shorting the test leads together. When measuring the
short I used, it still measures 0.05 ohms. I doubt that many folks doing
hobbyist work can measure the resistance of their short either. uant to
look into this. I am sure it is reproducible.

--
Bryan, WA5VAH

An interesting post Bryan.

I agree that the resistance of the short is unlikely to be an issue, but
the resistance will increase with frequency due to the skin effect.

To measure low resistance values one needs to use 4-wire Kelvin connectors.
But even without a meter with that facility, it is very easy to use a
constant current source and a decent handheld multimeter. Many cheap
handheld multimeters can read 100 uV easily. Pass 100 mA thru the DUT and
you a 1 milli ohm resolution.

Dave.

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom

On Tue, 15 Oct 2019 at 00:09, Oristo <ormpoa@...> wrote:

Do you have any gnuplot code which can import a Touchstone file and plot

it on the Smith Chart?

I do, now. Having only this morning first looked at Touchstone S1p files,
I discovered that they are already in gnuplot format,
which seems unlikely mere coincidence.

You are obviously a much more competent gnuplot user than me. I like it the
fact that I can use it non-interactively. The calibration kits I sell come
with about 10 graphs showing various plots such as the properties of
calibration standards, the verification attenuator etc. Manually plotting
that lot would be extremely time consuming and error prone, but being able
to generate all the PDF plots from a single unix shell script makes the
process much easier.

--

Dr. David Kirkby,
Kirkby Microwave Ltd,
drkirkby@...

Telephone 01621-680100./ +44 1621 680100

Registered in England & Wales, company number 08914892.
Registered office:
Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United
Kingdom

On Tue, Oct 15, 2019 at 03:42 PM, Rune Broberg wrote:

This looks very interesting, Bryan! I am happy that my little piece of
software has turned out to be able to do things like this ;-)

I am a little curious to see Smith chart measurements of your open, load
and short after doing this calibration adjustment - just to see how much it
changes how they look.

I have wondered a little whether allowing a pure resistive value for the
short would also be relevant?

I'm still looking for a good reference for the calculations for how to
compensate for a "load" standard that has a capacitive component: How does
that look? Is it just like the inductive phase shift with the sign
reversed? Could a load capacitance reasonably be represented by a negative
inductance?
--
Rune / 5Q5R

Rune,

Yes, your software can do a lot of things that I seem to need. Thanks, again, for continuing to work on this effort. You and your efforts are greatly appreciated.

I will cover the changes in the open, short, and load separately below. To get the plots shown here, I averaged 3 (or more) copies of 5 scans from 50 kHz to 900 MHz. The total number of frequency samples was therefore 505 samples or about every 1.78 MHz. Averaging is very useful and important in nanoVNASaver, especially when looking at these kinds of measurements, especially above 300 MHz.

First I'll talk about the open.

On the Smith chart plot little change is observable after the tuning is applied because the changes being made represent small changes in the phase of S11. In fact, to see the changes one has to look at the phase of S11 on a scale of about +/- 2 degrees. The S11 phase of the open is shown in the file "S11-Open-Phase-NoTuning.png". The change is such a small change in the phase, it is almost impossible to see anything on the Smith chart. The data is all clustered near the right side of the Smith Chart as it should be after an effective calibration. However, it appears to me there is real data in this phase plot, even after calibration but before applying any tuning to the parameters in the "Calibration standards" form. When I changed C0 in the "Calibration standards" form of nanoVNA-Saver to 1200 and the offset delay to -55 ps. This change produced the phase plot in the file "S11-Open-Phase-with-Tuning.png". Notice two things about the plot after tuning. 1) There is no "quadratic looking" drop in the phase as we move from low frequencies to higher frequencies as there was before tuning. 2) Although I did not do this, a linear fit to the data in the phase plot after tuning will be a horizontal line near zero degrees. This is the definition of an ideal open. Thus, while you cannot readily see such a small change on a Smith chart, there is some significance to the changes because we removed frequency dependent artifacts of the open I used in the calibration process. Please also notice from the amplitude charts in the first post in this series show some improvement in the trend of S11 in dB when measuring the open RG-213 cable. This is not very compelling, but read on.

Now let's talk about the short.

The short I used produced a nice dot on the left side of the Smith Chart after the normal calibration; however, there was significant ripple remaining in the S11 amplitude as shown in the plot below "RG-213-WithOpenOnlyTuning.png" I suspected, but did not know that could be the fault of the inductance in the short that was used in the calibration. By modifying the L0 parameter in the "Calibrations standards" form we can remove the inductance that may be present in the short I used. The resulting S11 amplitude plot is attached to the first post above and called "S11-RG213-WithCalTuning.png". Also, please refer to my post to Kurt in this thread that shows the vastly improved Smith chart for the RG-213 cable. The circles are now circles and they are much more closely centered on 50 ohms.

So, now to your question: What does the actual short used in the original calibration look like on the Smith chart once the L0 correction for the Short is inserted? The result is shown in the figure "Smith-OriginalShort-WithCorrections.png". This result should be exactly like a 1.2 nH inductor which is what I tried to remove using the L0 term. In fact, nanoVNA-Saver confirms this inductance after this correction is applied by indicating 1.2 nH is the "parallel X" when measuring the actual short. When the VNA is properly calibrated for a short, it shows the actual inductance of the physical device I used, equivalent to 1.2 nH.

In the case of my BNC short, I don't think I have the ability to reliably measure a resistance that small. The ohmmeter I have won't go lower than 0.05 ohms even when shorting the test leads together. When measuring the short I used, it still measures 0.05 ohms. I doubt that many folks doing hobbyist work can measure the resistance of their short either. Such small resistance values have little impact in a 50 ohm system. Therefore, I don't think there is benefit to including a resistor as a part of the cal correction for a short.

A discussion of the load follows.

I won't go into the details about the tuning I did for the load. A similar procedure to what was used for the open was used for the load. Here, again, averaging a lot of sweeps is important in order to measure the trends in the phase of a signal with a return loss of some 40 to 50 dB. In order to flatten the S11 phase of the termination I used for calibration I did need to add a very small amount of inductance (50 e-12) in the calibration form. This is the equivalent of trying to remove 0.05 nH, a small amount indeed. At 900 MHz that is a reactance of about 0.28 ohms. Certainly not huge in a 50 ohm system. Of course, this small change is unobservable on a Smith chart using the nanoVNA but it is clearly visible on the S11 phase plot.

Long papers have been written on all of the possible issues with trying to model various loads and what to do to compensate for various types of loads at various frequencies. I think there are too many topologies to deal with in this type of software. The capacitance can be in series with the 50 ohm resistor or it can be in parallel or there might be capacitance in series and in parallel.... The same can be said of the inductance. In my opinion, you could leave what you have in place and let folks work with it so long as you allow negative numbers everywhere. Then folks can think about things in whatever way they must as long as you are clear about what you are doing in the software with the non-ideal values entered in the various boxes of the "Calibration standards" box.

By-the-way - When I reset some of the values in the Calibration standards box to zero after putting in and applying values, nanoVNA-Saver 0.1.2 immediately crashes. You might want to look into this. I am sure it is reproducible. Right now, I don't recall which ones do it.

I hope this helps answer your questions.

Again, thank you Rune for making the nanoVNA-Saver software available. I find it particularly valuable and useful.

--
Bryan, WA5VAH

Thanks, Larry. I've tried these steps many times with no success.
Let me trace the path I've been taking and see if you can spot where I'm going wrong.

I followed your pointer to GenHu site

Read through his instructions titled Upgrade NanoVNA use DFU.pdf

Clicked on my desired .dfu, and download the file NanoVNA-H_AA_20191009.dfu, which I stored in the same folder as DfuSeDemo.exe.

Connected NanoVNA to Windows 10 USB port and started up NanoVNA in programming mode.
This generates a new directory named Universal Serial Bus devices, and it contains a driver named STM32 BOOTLOADER

I've seen screen shots of successful firmware updates, and they show this new file to be in the Universal Serial Bus controllers directory, and the driver is named STM Device in DFU Mode.

If I could get past this driver problem then I think the rest would fall into place.

In case nobody has made this public, below find some part numbers for useful or absolutely required fittings and adapters.

A couple of each are en route to me right now. (From Digi-Key. Not Mouser. I gave up on Mouser after three orders in a row were screwed up, costing me serious coinage and time lost for five different jobs.)

Digi-Key part numbers:
ACX1242-ND SMA Jack-Jack (like the one shipped with most NanoVNAs)
ACX1240-ND SMA Plug-Plug (exactly the opposite polarity of the 1242 above. Might be handy setting up a DUT, you never know...)
ACX1246-ND SMA gender - mender. This is a male to female converter
J10097-ND SMA to BNC converter. Most of my stuff is UHF connectors, SO-239 / PL-259, but I already have adapters for BNC for that.

Digi-Key (and likely Mouser, if you prefer them - I don't have a dog in this hunt so get it where you like) has roughly a thousand different SMA to --something-- adapters and fittings. (The SMA to SO-239 adapters are way-stupid-over-priced as far as I can tell, but most of the rest are just ugly expensive, same as everywhere else... Adapters and connection cables and fittings are going to wind up more expensive than the VNA itself, I am afraid.)

--
Wes Will
N9KDY