开云体育

On Sat, Jan 4, 2020 at 11:24 AM, gary wrote:

Besides the Steber article on the nanoVNA, there is an article on a "Simple Inexpensive Accurate Vector Impedance Meter" by Koehler on page 23 that describes the design of an instrument nearly identical to the nanoVNA. Good information on the design considerations and how it works, Thirdly, there is a Technical Note on page 32 from Stensby describing a method to determine coax cable losses by making open and short-circuit measurements of reflection coefficients.
================================================================
For those not aware, ARRL has made the associated files for the "Simple Inexpensive Accurate Vector Impedance Meter" article publicly available at, .

As gary noted, the design is built along the lines of the NanoVNA, however; it is a desktop box without a display. An DIY adapter for making coil and capacitor measurements, useable with the NanoVNA, is also included in the file archive.

- Herb

#106': On The Fourth Load VNA Trick

@Jeff Anderson - 4 January 2020
/g/nanovna-users/message/9153

Hello,

Thank you very much for interest in our work,
and especially for quoting this excerpt by us,
as well as for the opportunity you are giving
to us to improve it !

Well, we presume that you are not following
this thread from its very beginning. So, let us
try our best to reshape this excerpt, as follows:

"
Therefore, the Absurdness does not belong to us,
but to VNA itself, because:

(a) It considers by default that all the Standards
of the Whole World are identical and they have
values equal to those of their Names, that is of
their Nominal Values (-1,0,+1), and

(b) It handles these Standard values in the very
same way we use them, that is : with linear
S-parameter equations.
"
Does it have an enough crystal clear meaning now?

Sincerely,

gin&pez@arg

#106':

@Gary
Can you help me to understand the reply from g&p?

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

On Sat, Jan 4, 2020 at 11:51 AM, gin&pez@arg wrote:

Therefore, it not our absurdness the fact that VNA considers by default that
it is enough for it not only to consider All the Standards of This Whole World as
identically having values equal to those of their Names, that their
Nominal Values (-1,0,+1), but in addition to that Absurdness to handle them
in this very same frame of our SOW : with linear S-parameter equations...

gin&pez,

Please forgive me, but your writing style, in my opinion, contains much too much extraneous "verbiage," and it is difficult for me (and probably others) to wade through the unnecessary words and sentiments in an attempt to glean the actual point you are trying to communicate. Trimming your sentences and paragraphs down to the essentials would greatly help you to express your points.

For example, what is the point you are trying to communicate in the paragraph I have quoted, above? Are you saying that all VNA's consider their SOL standards to have Reflection Coefficients of (-1, 1, 0), irrespective of the actual Reflection Coefficients of those standards?

Or are you saying something else? If it is "something else," then could you please explain your point in a clear and concise fashion?

Thank you,

- Jeff, k6jca

#106: On The Fourth Load VNA Trick

@Erik, PD0EK - 4 January 2020 - /g/nanovna-users/message/9131

Dear Erik,

We would like to thank you very much because you revealed at last your Subjective
World. Now, there is a chance to understand each other just on the basis of logical
reasoning, of course.

Well, we already openly set the crystal clear limits of our SOW regarding the kind
of "VNA Measurements" : linear S-parameter equations and their consequences;
nothing more-nothing less, but exactly all of this. All that can be logically concluded
and reasonably described within these very limits - which, by the way, you already
accepted too by proposing to us that picture (alas, still self-contradictory) you are
hosting at your website.

That's all. Crystal clear.

Therefore, it not our absurdness the fact that VNA considers by default that it is enough
for it not only to consider All the Standards of This Whole World as identically having
values equal to those of their Names, that their Nominal Values (-1,0,+1), but in addition
to that Absurdness to handle them in this very same frame of our SOW : with linear
S-parameter equations...

Start at last putting the blame - if you think that is really one such - to where it is belong
exactly, that is to:

The Fourth Load VNA Trick

which comes from that Much Bigger than our Small Objective World SOW, that is from
The Objective World of Linear S-Parameter Equations. And remember, please, that we
didn't invented this World, we simply present what are the unavoidable logical consequences
for anyone who would adopted it, as a whole of course and not by selecting only those parts
of it who thinks he likes because he finds them as most convenient for his purposes - that is
to form a Subjective World instead of an Objective one.

Kind regards,

gin&pez@arg

#106:

Besides the Steber article on the nanoVNA, there is an article on a "Simple Inexpensive Accurate Vector Impedance Meter" by Koehler on page 23 that describes the design of an instrument nearly identical to the nanoVNA. Good information on the design considerations and how it works, Thirdly, there is a Technical Note on page 32 from Stensby describing a method to determine coax cable losses by making open and short-circuit measurements of reflection coefficients.

It occurred to me the T-check is the single vna equivalent of the vna comparison formula (ratio of cross ratios)
The T-check also works if you connect the same single load to port 1 AND port 2 which is exactly what is done in the ratio of cross ratios check.
The T-check compares the two directions of the measurement (port 1 to 2 with port 2 to 1) by taking the inverse of one direction and check if the ratio is one.
Seems the same approach. Correct?
--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

Thank you Lucio for the Web and Android client information! Happy New Year!!

On Sat, Jan 4, 2020 at 08:49 AM, Lucio I?LYL wrote:

A few answers to find here:

===============================================================

Thanks Lucio,
I had already found that article during my research. The pictures referenced in the article were first released at this forum by Gabriel. I've noticed in the past that much of the content regarding the NanoVNA that rtl-sdr.com generates seems to come from this forum. This forum is a trail blazer for other outlets in regards to good solid technical information.

Again, Gabriel's design efforts are well documented. Primarily looking for creditable resources regarding hugen's and edy555's concrete design efforts.

- Herb

- Herb

Very good on the saver. On the hardware side, the delay when entered handles the "de-embedding" or negation directly. In any case, a hands on exercise or experiment is probably with a ton of arithmetic. So try this:

You can readily do this at HF, say calibrate from 100 kHz to 30 MHz. Make yourself a nice 220 ohm load, I used a small 1/8 W resistor. A chip R would be great. But just about anything that is for the most part NON REACTIVE at HF will be fine. Place it at your CH0 port as though this is you antenna under test.

You should see a nice tight single dot on the Chart at 220 ohms.

Now I took a nice piece of 50 ohm cable, TLINE. It was maybe 4 or 5 feet long. Place the 220 ohm R at the END of the cable. Now look at the swept chart s11 trajectory, looking into the cable with you vna. It will be a sweeping arc starts out at 220 ohm and moves clock wise with an ever decreasing R value. The 220 ohm resistor value appears at the input as a new value as altered by the TLINE.

Now, will de embed the TLINE by using the vna electrical delay feature. I dialed in about 13500 psec and your value will be different based on you length of TLINE cable. As you enter in new values of electrical delay you will note the CW rotation of the 220 R begin to collapse back to the original measured dot.

You have de embedded the transmission line. Can you calculate the exact value of delay required? Sure.
Depending on the physical nature of the cable, you can calculate the exact delay. If the cable is well behaved, i.e. uniform, this works very well.

Alan

Be aware you have to enter a negative offset delay in the calibration panel of nanoVNA-saver when de-embedding a cable or stripline
But it works!

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

A few answers to find here:


--
*73, Lucio I0LYL Rome, Italy*

Gabriel Tenna White's version 2 hardware and firmware design efforts are well documented on this forum and on her GitHub pages. Hugen and edy555 reportedly have version 2 efforts in the work, but so far, nothing as concrete as Gabriel's design. Hugen has documented a 4-inch F303 branch, that admittedly is not a version 2 design.

I was just wondering if any forum members have come across credible resources where either Hugen's or edy555's version 2 designs could be followed. My own research has not turned up anything close to what Gabriel has released, but I have not delved into any foreign language resources.

Since edy555 originated the NanoVNA design, I'm surprised he is not at the forefront of the V2 design effort. Gabriel's V2 design appears to have leap-frogged both his and hugen's. Still, its early in the race and the anticipated 2020 releases of the NanoVNA V2 show great promise.

- Herb

Next to the 25ohm check and the T-check, Kurt wrote an excellent proposal on how anyone can check another aspect of the quality of the calibration
/g/nanovna-users/message/4609

What can we use from this "errors of "errors"" discussion to help the community?
Till now I find it extremely difficult to come with something practical

--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

I guess this is why R&S introduced the T-check many years ago as a simple approach to establish quality of measurement

In my own simple words, L calibration establishes the center of the smith chart, O and S define the boundaries so using a fourth known load such as 25 ohm (being substantially different from the 3 calibration loads and easy to create using two calibration loads and a Tee) shows the accuracy in one direction This for sure does not eliminate the amplification of errors when moving away from Z0 but at least gives a understandable indication of quality.

For the nanoVNA this has proven very valuable as the calibration was perfect till 900MHz but the T-check (or a measurement of 25ohm (almost) pure resistance) showed considerable opportunity for improvement.

As the T-check can be done using any impedance it allows any user to establish a sense of measurement accuracy at the used impedance.

It is my strong wish to translate thave this lengthy thread translated into something practical a average nanoVNA user is able to understand. For that reason I was asking about the choice of the 4th load to ensure the % error in the cross ratio has a real meaning. "substantially independent" is not usable for the average user. Is 25 ohm substantially different? A pure capacitor but at what reactance?. It would be of benefit to the community (that has to endure the many mails on this subject) to have simple guidelines that can be applied easily with relevant meaning
--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK

On Sat, Jan 4, 2020 at 06:08 AM, Gary O'Neil wrote:

I believe the reference to "absurdness of identicality" was with respect to
the notion that different load values... which, when calibrated, produce
identical results (-1, 0, 1); and those results are expected to yield
perfectly corrected and accurate measurements.

Gary, are you saying that different "characterized" SOL standards, when measured after calibration, produce identical results. (-1,0,1)? If so, this is not true -- they produce the results equivalent to their modeled impedance (a model represented by a cal kit's calibration coefficients).

And therefore, the more accurately one can model this impedance (for example, using a 3rd-order polynomial to describe the fringe capacitance of an "Open" load) , the more accurate will be the measurements.

Are you saying this is not true?

...Through this process, the common user becomes satisfied with the
accuracy of the measurement, unaware of the in inaccuracy introduced by their
attempt at improving it.

Not sure what you are saying, but if you increase the accuracy of the models of the standards you increase the accuracy of the measurement.

I am also puzzled by this quote in your earlier posting...

the also very revealing and important consequence of polynomial error
correction attempts; and my observations... FACUPOV... of their uselessness,
and the propagation of their contributions to uncertainty in the otherwise
straight forward definition of the uncertainty boundary profile.

Which "polynomial error correction attempts" are you referring to as being useless? The fringe capacitance polynomial? Something else?

Thanks for any clarification.

- Jeff, k6jca

I had what seems to be the same problem, but with the last version, updated Windows Vista Professional. The error message was "could not load Qt platform plugin "windows" in "" even though it was found."

I was unable to find a solution, except for the recommendation you also received - use Linux. To which I had the same objections as you have.

Good luck! I really hope there's a solution.

Doug

I find it interesting that some very educated folks like Dr Stebers are quick to critique things but you rarely see them helping with the creation of improved documentation or helpng others on the forum for something like the Nanovna.?

At least there are other very knowledgeable experts on this forum from around the globe who are willing to contribute to the increasing sum of knowledge on this forum with value added tips, techniques, documentation and personalized help in many instances and all the participants are to be heartily commended.?

Cheers to all for 2020!
Looking forward to the new V2 forum (?) Maybe coming soon ?


On Sat, 4 Jan 2020 at 9:49 AM, Nick Kennedy<kennnick@...> wrote: His overall impression seems pretty favorable - like many of us amazed that
such performance could be available at such a price.

He found impedance measurements to be very good in the range of 12 to 200
ohms and acceptable from 5 to 500 ohms.

He cautions potential buyers that clones appearing on the market might be
of varying quality, and that available manuals might be poorly translated
from the original Japanese or Chinese.

Otherwise, " ... if you like to play with hardware and software you may
find this little gem an wonderful toy for experimentation."

73-

Nick, WA5BDU

Search under the concept of de-embedding and on the vna you will use the function electrical delay.
73' Alan

Pentium 4 machines (originally with Win XP) run very nicely with any of the popular Linux distros (like Linux Mint 19.3) ,obviously 32 bit .
With a ( nowadays low cost) SSD the system is fast . Go for it !

I know that. As a matter of facts, on this PC I have a dual boot with Debian Buster. And the main HD is an SSD (I have 4 additional disks on this tower).
Yes, I could boot with Debian and run nanovna-saver under it, but all of my ham software (also that written by me) is specific for Windows....
So I would like to be able to run that utility when booted with Windows.
But the reports from others that say that they are able to run it under Windows make me think that maybe there is something to be adjusted on my installation. It is Windows XP Professional, SP3, but now I have the suspect that some Python library must be missing... the programming language of the utility seems to be Python... I have to investigate a bit deeper.

Thanks to all the suggestions.

Alberto