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Oristo,
My reading of Alan's post is that he performed a normal OSL calibration at port 0. After that he connected his shorted clips to port 0 and noted the difference between the OSL short and the fixture (test lead) short which was 300 nH. He then measured the inductor and subtracted the 300 nH fixture inductance for his final value. No "Mickey Mouse" calibration involve. I'm sure Alan will correct me if I misread.

Herb

Hi Alan -

This measured value of above returns 1.37 uH.
Now I must remove the stray 300 nH and I arrive at a corrected value of 1.07 uH.
This value correlates with an independent vector Z meter measurement within 50 nH, measured at the same operating frequency.

I would be very interested to know what value is reported by nanoVNA for that inductor @ 3 MHz
after "Mickey Mouse calibration" by short, open and ~ 50 Ohm resister in alligator clips.

Herb,
the "cutoff frequency" is the -3 dB point. I should make that more clear, I
suppose :-)

--
Rune / 5Q5R

Rune,
The international definition of bandwidth is actually the -3 dB points. That is what most manufacturers mean in their literature unless specified otherwise. The -6 dB and -60 dB points are more often used when specifying receiver bandwidth if my time in the military serves me correctly. Wouldn't hurt to include all three for the inevitable request you will probably receive.

Herb

Hi Bryan,
I just confirmed by installing 0.2.2 on my NanoVNA that it does indeed have
problems interfacing to my application. I have asked edy555 about it on
Twitter, and for my own testing purposes, increases the delay to 1 second -
which fixes the issue, but also makes the software feel *a lot* slower.

I need a 1500MHz firmware for some of the tests I'm making at the moment,
though, so I will stick with this for the next few days at least.

--
Rune / 5Q5R

On Wed, 2 Oct 2019 at 16:45, bryburns via Groups.Io <bryburns=
[email protected]> wrote:

Rune,

Thanks for the tip on using Hugen's firmware. I finally found the latest
version of his firmware which has TDR capability and works with both
nanoVNA-Saver 0.0.12 and 0.1.0. The version of firmware I am now using is
NanoVNA-H__900_ch_20190924.dfu which I downloaded from

.

I no longer have issues with getting bad data at the start of scans where
the frequency has changed. I can use any number of scans and the data is
correct.

I am just beginning to look at other features of the newest version.

Bryan

On Tue, Oct 1, 2019 at 08:58 AM, Rune Broberg wrote:

Hi Bryan,
sweeping currently works as follows:
1) The requested frequency range is set (start and stop frequency)
2) A delay of 300 ms
3) The frequencies are read back by sending the text "frequencies",

waiting

50 ms, and then reading them
4) The S11 data is read (again, 50 ms delay included)
5) The S21 data is read

I decided on 300 ms after testing a few times, and figuring that it was
"probably fine". Setting no delay sometimes let to errors, and more than
250 ms seemed to be fine, so I set it to 300. Maybe it's too low? But
then I was using Hugen's firmware.

If you can make a non-continuous sweep that produces a noticeable error,
you can try exporting the S1P/S2P Touchstone file, and looking at the
frequencies. The Touchstone export reads the exact frequencies reported
back by the NanoVNA, so it should tell you what frequencies it thinks

it's

reporting data for.

Sadly I don't think it's something I can really address in the

application

- I believe it has to be accounted for in the firmware.

Thanks for the work you're doing on this issue, though! Good luck with

it!

--
Rune / 5Q5R

On Tue, 1 Oct 2019 at 16:40, bryburns via Groups.Io <bryburns=
[email protected]> wrote:

Rune,

Thanks for taking a look at this thread!

My biggest concern is that with the firmware 0.2.2 from edy555 I always
see incorrect data in the second scan when using 2 scans between 80

and 120

MHz. With a single scan there are no errors over the same frequency
range. The incorrect data is always wrong in the same way. I.E. it is
actual measurements but they are from the wrong frequencies. If I do 5
scans, it appears that the first part of scans 2 through 5 is almost

always

incorrect data. If it were occasional errors, I could work with it;
however, it is repeated with my nanoVNA and this firmware. When I

request

a single scan over the exact same frequencies as the 2nd or 3rd or 4th

or

5th scan, I very rarely, if ever, see an error in the nanoVNA-Saver

data,

even in continuous sweep mode. What is different about continuous

sweep

mode? Is there a pause between the scans?

I very rarely, if ever, see it with firmware from hugen dated August 2,
2019 using the exact same scan settings 2 or 3 or 4 or 5... Yes, I

will

occasionally see errors with the hugen firmware but they are quite

rare and

usually pretty obvious. Repeating a sweep or measurement will clear

the

errant data.

I don't know much about the transfer protocol between the nanoVNA and

the

PC. From your comment above, I would have to assume that you do not

get

the frequency information in the same message as the data so there is

no

way to throw out data based on the fact that the frequencies you

requested

are not the frequencies sent from the nanoVNA. Is that correct?

A few questions, mostly thinking out loud. :>) I wonder if data is

being

sent from the firmware before the hardware has actually stabilized at

the

new frequencies you have requested? Would it help to pause a bit after
requesting a new set of frequencies?

I will continue looking for more clues to this issue.

--
Bryan, WA5VAH

--
Bryan, WA5VAH

On Thu, 3 Oct 2019 at 22:14, Oristo <ormpoa@...> wrote:

You got a nice smith chart blank on one side to photocopy and own use

etc :-)

Here is a Smith Chart that need only be printed:


It is generated using gnuplot, my favorite data plotting package:


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

it on the Smith Chart? I produce all my plots for VNA cal kits usin
gnuplot, as one can automate everything, reducing the risk of errors. But I
have never plotted it on a Smith Chart - only amplitude and phase on the
same graph, using two y-axes,

My company logo has a Smith Chart in it - I generated that with gnuplot.

Dave
--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

On Thu, 3 Oct 2019 at 21:38, Bear Albrecht <W5VZB.NM@...> wrote:

Here's United Parcel Service's reference material about shipping Lithium
batteries:


Covers air and ground, and lithium ion and lithium metal. Flow charts
galore.

There's more stuff out there on the web that I'm still reading.

W5VZB

Test certificates, flow charts, not more than 30% charged, 27 pages in
length. Irrespective of what air regulations state, a lot of couriers have
much more restrictive practices. I wanted to get a battery for my
multimeter some time ago, and Digikey had exactly what I wanted, but would
not ship it to the UK. The small batteries from Farnell are often in
containers with warning labels on the outside. The courier company probably
insists on it.

I can understand why some sellers ship batteries - it makes their products
more attractive. I can understand why others will not - they feel it is too
risky.

I had a VNA calibration kit returned once from one country (forget which),
by a courier (DPD) as it was considered dangerous goods.

I had another VNA cal kit get held in customs somewhere, on the basis of it
being dangerous goods. After making various comments, the courier was
finally satisfied the goods were safe, so they were accepted. I can imagine
if anything has batteries in it, there's a far greater risk of things being
returned or even destroyed if a courier does not want to handle it.
--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

You got a nice smith chart blank on one side to photocopy and own use etc :-)

Here is a Smith Chart that need only be printed:


It is generated using gnuplot, my favorite data plotting package:

Same here, but i stil i no negative Feedback for the seller. Strange.

Indeed. Downmixing retains phase difference

If you like to build a clone from the sdr-kits *Testboard*,
just use a FR4 veroboard 35 x 27 mm and solder 7 x 7 IC socket pins
and 2 SMA female plugs with a paper model, what you can get from
the web site

You need a few more IC socket pins for jumpers and samples to measure.

See the attached photos.

73, Rudi DL5FA

W5VZB

Here's United Parcel Service's reference material about shipping Lithium batteries:

Covers air and ground, and lithium ion and lithium metal. Flow charts galore.

There's more stuff out there on the web that I'm still reading.

W5VZB

On Wed, 2 Oct 2019 at 20:51, alan victor <avictor73@...> wrote:

Good day,

When I began this process of working with the NanoVNA, I was not certain
how the cal standards were being treated. Since the completed cal showed a
perfect open, short and termination, I was pretty certain they were NOT
defined as REAL SMA connector devices! The SMA connectors are NOT that
perfect!

Alan

Ignoring random errors (noise, repeatedly of connectors etc), the standards
should look perfect opens and shorts, i*f that is how they are defined. *You
could use an SMA plug with a few cm of wire and leave it open to make your
open, and put your short on the end of a few cm of wire. If the calibration
standards are defined to be perfect text-book opens and shorts, they would
look like that on the Smith Chart. If you then put the supplied short on
the VNA, that would look wrong.

The female standards supplied with the kit are not bad at all. The problems
are going to occur when using most other connectors - everything except
APC7 is going to have some problems.

To check if I understand this correctly I ask, There is also a phase difference between reference and difference voltage from a bridge. I should have remembered that. And now they are mixed to 5kHz to make it easier for DSP and so on.

I may start this as a new thread titled Measurement of Components... again.

In any case, I put together the nice n' easy alligator BNC connector interface which is easy to deal out.

The part under investigation is a 1 uH inductor whose SRF is above 150 MHz. Nice. I can measure it down at 3 MHz or so with no worry about SRF complications.

I do a shunt mode measurement, one port only and a SOL calibration directly at the VNA CH0 port.
The frequency range is 1-30 MHz, 101 data points. I then add on the BNC alligator clip interface to the VNA.

My first observation is that this test set system with the alligator clips open and laying on the table has a shunt C of 10 pF at 3 MHz. I then short the clips together and find that the series inductance of this test system is 300 nH.

Next I connect my 1 uH inductor and note the CW movement of the chart with a readout of 1.37 uH at 3 MHz. I have at this point an inductor under measure with a shunt C of 10 pF and a series L of 300 nH.

I can remove the shunt C first by noting that the measured reactance must be of the form of the product over sum of the DUT and the shunt C of the fixture. Hence, the actual reactance measured, Xa must be:

Xa=(Xc*Xm)/(Xc+Xm) where Xa is the actual reactance of the DUT, Xc is the shunt C of the fixture and Xm is the measured reactance. You will note, if the Xc value is significantly LARGE then Xa=Xm and the only fixture component that I would have to remove is the stray series inductance.

The measured value of above experiment returns an Xa equivalent to 1.37 uH. Now I must remove the stray 300 nH and I arrive at a corrected value of 1.07 uH. This value correlates with an independent vector Z meter measurement within 50 nH measured at the same operating frequency.

Key here, you must calibrate with know standards to remove the aberrations-imperfections of the VNA instrument hardware, this is level one. Then level two must address the inherent parasitic values of the test set. This is essential. Then apply the appropriate arithmetic to find the unknown DUT itself.

Alan

Mike,
see attached for a first sneak peak of what I'm working on.

I think I'm currently under-estimating the roll-off by measuring it from
the -6dB point and to the end of the data. Is there a norm for how to do
these measurements? Or should I just make it up as I go along?

[image: image.png]

--
Rune / 5Q5R

On Thu, 3 Oct 2019 at 15:45, mike watts via Groups.Io <wy6k=
[email protected]> wrote:

Yes, all of those filter measurements would be useful for things I do.
Those functions would elevate you from "hero" to "demi-god" in my world.
:-)
Mike WY6K


"... somewhere in the distance, there's a tower and a light, broadcastin'
the resistance, through the rain and through the night..."

On Thursday, October 3, 2019, 4:20:50 AM CDT, Rune Broberg <
mihtjel@...> wrote:

Hi Norbert,
the application can run calibrations at far more than 401 points - I have
certainly done 5050 points at one point. ;-) But it does this in the
application, and not on the device, due to the hardware limitations.

I agree that a function to find cut-off frequencies for filters etc. would
be interesting, and I've put it on the list of features I would like to
implement for the next version, ie. for next week. I don't make any
promises though :-)

What measurements would be relevant to provide? Cut-off frequency, span for
band-pass, dB/octave and dB/decade fall-off, pass-band ripple?

--
Rune / 5Q5R

On Thu, 3 Oct 2019 at 11:12, <norbert.kohns@...> wrote:

Hi Rune,
thank you for fixing this issue!
I have a question for you in respect to the required number of data

points

to measure a band pass filter. With 101 points it is most likely not
possible to find the -3 dB points because the sample point is way off

from

-3 dB on both sides of the band pass. With 401 points it would work. An
automatic feature of measuring the bandwidth would be absolutely cool!

The

TAPR software is able to perform a calibration at 401 points or even more
than that, so I am certain that you could do that as well. I have no

glue

on how difficult that would be, but more data points for calibration

would

be a huge improvement.

Kind regards
Norbert, DG1KPN

Rune,

Thanks for your kind comments.

Here are some suggestions regarding your 4 questions above.

1) What window do I recommend?

A Blackman window has very low peak sidelobes (< -58 dB) which is unnecessary in a TDR application using a nanoVNA. The Blackman window achieves this at the expense of impulse response width. The pulse we see on the screen is wider than it needs to be. You could narrow the impulse response a bit by choosing a window with higher peak sidelobes such as a Hamming window (-43 dB peak sidelobe). The peak sidelobe of a Hanning window is <-31 dB which is a littler higher than I would recommend; however, it would be an acceptable choice for many applications. Make sure that the length of the window and the length of the samples in the frequency domain from the VNA are the same length. And, you window both the real and imaginary parts of the data in the exact same way.

2) Should you zero pad the data?

I would recommend zero-padding the data. I can't be sure but it appears you are already doing this based on what I see in your TDR plots. What I am seeing could be, in part, an artifact of the Blackman window you have chosen. Zero padding has the advantage of interpolating the time-domain data for the user. This enables more precisely estimating time delay for cable length if the cable is open on the far end from the nanoVNA.

3) How long should the IFFT be?

I would multiply the number of samples in the S11 data by at least 2 (4 would be better for frequency data of less than 500 points) and then take the next higher power of 2 for the IFFT length. If you are not familiar with how to do this. Here goes. If n is the number of samples (say 505), you use the equation IFFTlength = 2^(integer(log10(4*n)/log10(2)+1)). Basically, the log10(x)/log10(2) is the log base 2 of x. So for 505 samples from the VNA you would use a 2048 point IFFT of the windowed (see above) 505 samples from the nanoVNA. An even longer FFT won't hurt (n*8 in the equation above); however, it is probably not important to any measurement that comes to mind using the nanoVNA.

Changing the IFFT length does change the time-domain scaling of the samples being plotted compared to a non-zero-padded version. The relationship is inversely proportional to the IFFT length. In-other-words: the zero padding gives better time-domain sampling in the data. The window function chosen dictates the 3-dB width of the impulse; however, the length of the IFFT determines the time-domain sampling of the output.

4) What part of the output should be displayed?

Most IFFT algorithms will place the data we are interested in within the first half of the IFFT output. That appears to be the case for what is shown in version 0.1.0 of your great software. Therefore, you can just plot the data from the first FFTlength/2 samples. Of course, you need to plot the absolute value of the complex numbers out of the IFFT. I am pretty sure you are already plotting the absolute value.

I hope this helps with your continued development of nanoVNASaver. It is already a great tool.

Let me know if you have any questions.
--
Bryan, WA5VAH

On Thu, 3 Oct 2019 at 18:03, Henning Weddig via Groups.Io <hweddig=
[email protected]> wrote:

according to ebay my order is just shipped. It was marked shipped with a
a tracking number, so I can track the status of the shipment.

Henning Weddig

Same here, but clicking on the tracking number says that the label has been
created, but not actually shipped yet.

If this was $200 I would be a bit more concerned, but $20 is not much
money. If the VNA doesn’t show up, and it takes me a couple of months to
get my money back, I am not bothered.

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

No problem. There are many names around for the same file.That is why I uploaded them in the files section and dated each one.
Forum member ORISTO has created a WIKI page that describes the various releases:
Firmware Versions (with links)?by Oristo Po

More Forum member should be browsing through the WIKI /g/nanovna-users/wiki and FILES? /g/nanovna-users/files sections of this group.
There is a TON if info in there folks !!
And don't forget to print a copy of the Oct 2nd User Guide (29 pg) for reference while you're at it.
/g/nanovna-users/files/NanoVNA%20User%20Guide-English-reformat-Oct-2-19.pdf