开云体育

This will mainly interest the DUTCH speaking members

I posted two videos on YouTube with my presentation on the NanoVNA

Part one is about complex impedance, transmission lines, S-parameters and the Smith Chart (approx 2 hours)


Part 2 is about the NanoVNA and its applications (approx 1 hour and 45 minutes)


Veel kijkplezier !

Luc ON7DQ

On Wed, Jan 1, 2020 at 09:55 AM, Birdman wrote:

Even easier (AND cheaper!), he could have Amazon sell them. He could "sell"
amazon 10, 100 or 1000 units and let them list, sell and ship them. He gets
paid, the item is listed to billions of users, and when we buy it, it is at
our door step the next day in most cases.

Regards,
Chris

Amazon has become a disaster. You never know from whom you are getting the product even dough you might have purchased from a specific seller and saw a specific picture of the item. If the sale is fulfilled through Amazon they can choose the product that will we sent to you from any sellers that claim to be selling the same item and ship from a location that most suits them, even if the product is only similar but has the same name and you might end up with something that is different or possibly not exactly what you wanted to get. Let alone all the counterfeit stuff that gets into the mix and that they (Amazon) don't give a fig about. And it might get even worse if you order multiple items, they will break up your order into multiple packages as it suits them best. That is why I try to avoid Amazon as much as possible. At least on ebay you will deal directly with a specific seller and are looking at the pictures of what you will get, and shipping is for the most part free, no extra "premium" fees required. Granted there might be from time to time problems on ebay with a few sellers, but in my 18 year experience buying through them they are easily dealt with and from my point of view service from the buyer's perspective has only been getting better with the "Concierge" service that costs me nothing. Then even once gave me a $500 voucher because a seller was slow to reimburse me and to cancel the purchase. When I asked what to do if I eventually I got reimbursed they said "keep the voucher, its yours and you can do with it whatever you want". So yes I am a bit partial to ebay, wouldn't you if you feel you are being treated well? Just my 2 cents.

It is about as good as you can get without a good TDR instrument.

The objective of looking for high Z resonance peak at quarter wavelength is to verify Vp. Stray reactance on the 50 ohm port will create some error in this measurement. Inductance of stub grounding also needs to be minimized.

To minimize effects of these strays it is generally better to do the Zo measurement at lower frequency (1/8 to 1/2 of intended use freq) with longer length stub line.

5% off on Vp yields about 8% off on Zo calculation.
10% off on Vp yields about 18% off on Zo calculation.

KV5R,

They are the handout for the courses on antenna and feedlines.
As such they are often read this, evaluate this question.

If your going to suck those files up, then get the books that go with them as many
do reference them for reading. If not you are just wasting disk space.

Allison
-----------------
No direct email, it goes to bit bucket due address harvesting in groups.IO

Folks, if you want these please remember that you may be accessing a system that is supposed to be restricted to University of Kansas students who pay for the courses associated with these files.?
Anyone in the US copying and then sharing the files could be in for a ton of trouble so please be careful.




On Sun, 5 Jan 2020 at 3:24 AM, David J Taylor via Groups.Io<david-taylor@...> wrote: Thanks, Dave!
If you remove the filename from that link, e.g.,
, there's an index of over 300
RF engineering course files there! I collected them all... :-)
--KV5R
=====================================

Any chance you might put them all into a single Zip file for others to
access?

Thanks!

73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

Thanks, Dave!
If you remove the filename from that link, e.g., , there's an index of over 300 RF engineering course files there! I collected them all... :-)
--KV5R
=====================================

Any chance you might put them all into a single Zip file for others to access?

Thanks!

73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

Many VNA's use a wheatstone bridge (few use V/I measurement). A wheatstone bridge has a design Z0 for which it provides most sensitivity. Z=(R-Ro)/(R+Ro)
This graph shows the output of the bridge depending on R for a R0 =50ohm.

As most RF systems are designed with a Z0 of 50 ohm the VNA designers chose to balance their bridge at Ro=50 ohm to provide most sensitivity around 50ohm
So yes, you can calibrate with a different load but you do not gain anything as the bridge is used in a less sensitive area. This can be easily verified by trying to calibrate with a Ro=5kOhm. YOu will observe more noise.
What you should do (if the VNA allows) is to replace the internal bridge reference R0 with a different value to regain sensitivity at the new Ro and than calibrate with a load of the new Ro.
This is why people have been asking for how to use the nanoVNA with an external bridge where it is possible to replace the reference R0 with a different impedance.



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

On Sat, Jan 4, 2020 at 10:11 PM, Gary O'Neil wrote:

Three port terminations are identified as sufficient to represent a short
circuit (zero ohms), and open circuit (infinity ohms), and a load standard (Z0
+/-j0 ohms). These devices are measured and plotted on the display at the
locations representing the reflection coefficient values they are intended to
represent (-1 +/-j0, 0 +/-j0, and 1 +/-j0

Gary,

The point Jef wants to make is that above statement is NOT true for well characterized but non perfect calibration standards. The characterization (polynome) will describe where for instance the "open" should be seen on the smith chart. The same is true for the load. Adding a first characterization in the form of a small constant C makes the load move away from 0+j0 at higher frequencies. So the characterization of the calibration standard is not there to fix them at -1 +/-j0, 0 +/-j0, and 1 +/-j0 but to have the actual impedance reflected

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

GIN&PEZ, Erik, Jeff, et al;

Absurd and it's derivatives is probably not the most descriptive of the points being made. Consider this a trigger word that translates with emotional overtones. As all of us are aware, emotions can rapidly remove us from reason, and terminate useful and credible dialog. That said, absurd is an excellent choice, but only to those who have been following this thread in great detail, and contextually understand the word choice.

To those who aren't quite up to speed on where this project has arrived, it roughly translates to: "It is unbelieveably incredible that, since its invention, so much emphasis has been placed on VNA calibration with maximized precision, when it contributes more to errors and uncertainty in the results than enhance accuracy."

I have devised a simple VNA hardware description and one-port experiment that I think will demonstrate and illuminate the implications of this project, and reveals how the VNA relates to any user... at least in a one port environment The object of the experiment is to give readers an intuitve sense of what has been revealed in this thread; and provide sufficient understanding of the results to motivate them to challenge their current beliefs. It takes effort to follow the details sufficiently to comprehend its implications, and then study and defend the logic, reasoning, explanations, and conclusions that follow.

For much of this to make sense though, selectively challenging points of interest and comparing it with what the reader may already know and/or believe, may only serve to confuse and make the task of understanding difficult.

A descripton of the VNA hardware used for one port impedance measurements.

The common user views the VNA as a Smith Chart; a circle which represents the Mobius mapping of the complex plane from zero to Infinity centered at Z0 and often (not always) normalized to 1 +/-j 0 ohm.
By definition; maximum power is absorbed by the load when the load is equal to the characteristic impedance of the source (sometimes normalized to 1 +/- j0) . No power is reflected, the reflection coefficient is zero, and this minimum reflected power condition (measured as zero voltage) is displayed at the exact center of the chart.
A calibration process is required to establish the center of the chart as representing the characteristic impedance of the system, and to restrain all values of reflection coefficient to within the unit circle.
Three port terminations are identified as sufficient to represent a short circuit (zero ohms), and open circuit (infinity ohms), and a load standard (Z0 +/-j0 ohms). These devices are measured and plotted on the display at the locations representing the reflection coefficient values they are intended to represent (-1 +/-j0, 0 +/-j0, and 1 +/-j0 which also represent the complex real impedance locations of 0, Z0, and infinity ohms respectively).
Note that these points are plotted as precise and ideal, and as with the Smith Chart, these points being identified is sufficient to plot the entire complex impedance domain from 0 to infinity centered on the characteristic impedance of the measurement system.


An illustrative experiment of the power and utility of the VNA, and the unnecessary constraints of other than nominal valued measurement standards.

Augment your set current of SOL standards with two additional resistive loads of reasonably equivalent quality. I chose 200 and 500 ohms for my experiment.

1) Perform a normal calibration of your VNA. Observe where the Short, Load, and Open appear to verify your calibration was successful. Measure and record the value of your two newly created loads.

2) Recalibrate your VNA using one of the new loads as the load standard (e.g. 200 ohms). Observe where the Short, Load, and Open appear to verify your calibration was successful. Measure and record the value of your two remaining loads.

3) Repeat step 2 using the last of the two new loads.

Do not be concerned with what you observe during this experiment. You will become informed. All calibrations will result in the load always being in the center.

*

The following is what I expected to observe and my measurements were in agreement with this:

A) For test case 1, using my current set of standards, I measured the anticipated values of 200 and 500 ohms real as displayed on the NanoVNA.

B) For test case 2, using my 200 ohm load as the calibration standard, I measured 12.5 ohms real for my original 50 ohm calibration standard, and 125 ohms real for the 500 ohm load.

C) For test case 3, using my 500 ohm load as the calibration standard, I measured 5 ohms real for my original 50 ohm calibration standard, and 20 ohms real for the 200 ohm load.

Notice that my A results are the correct values of the newly constructed loads... This is because the NanoVNA firmware assumes my measurements were made in a 50 ohm measurement environment and scaled the display for Z0 accordingly.

In my B measurements, the NanoVNA makes the same assumptions about Z0. This is a fixed value in the firmware. However this wasn't the environment I calibrated the system to measure. I defined Z0 for my measurement to be 200 ohms, but the NanoVNA displays its results based on its Z0 assumption of 50 ohms.

Corrrecting my B results by an appropriate scaling factor of 200/50 = 4, I simply multiply the NanoVNA readings by 4 and this becomes 4 * 12.5 = 50 ohms and 4 * 125 = 500 ohms, thus my displayed results are as expected.

In the same manner, multiplying the results in my C measurements by the Z0 scaling factor of 500/50 = 10, my measured results become 10 * 5 = 50 ohms and 10 * 20 = 200 ohms, and the displayed are again as expected.

Probe around your NanoVNA while performing this experiment. You will make some obvious but unsuspecting observations. For example the VSWR of the 500 ohm load is 10:1 when calibrated in a 50 ohm measurement environment, but when calibrated in a 500 ohm measurement environment, the SWR is 1:1 and flat across frequency, and the 50 ohm calibration standard is 10:1 and flat across frequency.

So what does all of this mean from a common user's point of view (FACUPOV)?

The VNA is exposed as nothing more than a complex ratiometer. It displays the ratio of a reflected wave to a transmitted wave. This is of course the definition of the reflection coefficient. This is also the condition displayed graphically on a Smith Chart.

Measurement accuracy is strictly defined by the accuracy in which the ratio can be resolved, and the known/characterized/accepted true value of the reference to which it is compared (user defined as ZO).

Errors and uncertainties are measured, remembered and not introduced into the results... e.g. the uncertainty of using measurement hardware having a dramatically mismatched (10:1) Z0 source impedance is transparent in the measurements.

Amateur radio operators are resourceful creative and inventive creatures. It won't take long for us to realize that we can calibrate our instruments in any arbitrary impedance of our fancy, moving the results closer to the center of the Smith Chart where its displayed behaviour is expanded and made more optimally visible and easier to analyze.

Most intriguing about this project is that through all of the work that has been put into bringing these new perspectives to our attention, nothing needs to change in either hardware nor software; although opportunities to make it more efficient have been revealed along the way.

The requirement for precision calibration standards correction was dismissed when the automatic network analyzer system was first described in 1968, but ignored until now. Perhaps that really is a bit of an absurdity. :-)

--
73

Gary, N3GO

On Sat, Jan 4, 2020 at 03:55 PM, gin&pez@arg wrote:

Hi gin&pez:

After that said, also allow us, please, to consider now that our way to use
this mathematical model, that is * w i t h o u t * the introduction of additional mathematical
expressions, is by this very fact the most simple way to confront with this really existing issue
- which by way, it also covers the non-default operation of your VNA - simply because our way
covers the measurements by * a n y * VNA.

What additional mathematical expressions are you referring to?

If this is your mathematical model:

G = (S*(L-O)*(g*s+l*o)+L*(O-S)*(g*l+o*s)+O*(S-L)*(g*o+s*l))/
((L-O)*(g*s+l*o)+ (O-S)*(g*l+o*s) + (S-L)*(g*o+s*l))

Then, to create *accurate* representations of S. O. and L, you must derive the values of S, O, and L in a similar fashion to how they are derived for any other VNA that uses the standard 3-error-term one-port calibration technique. Are these SOL calculations the additional mathematical expressions you are referring to?

And at this very point also allow us, please, to emphatically declare that we
don't find anything erroneous in our point of view, that is the one From A Common User
Point of View FACUPOV, since we already looked ahead to exclude VNA cases in which this
default operation it is not their default. Our claim still holds for all those
still existing VNAs which do consider by default such an Absurdness.

Finally, allow us, please, to also emphatically say that * I F * after all
that provisions of your VNA, the unknown load value is still * c o m p u t e d * using the
expressions which are consequences of this very net linear S-parameter model,
* T H E N * you have not get rid off the Core Uncertainty of the Measurement still existing :
(a) in your Standards,
as well as (b) in the inaccuracy of your VNA readings.

My apologies, I do not understand the point you are trying to get across with the above two paragraphs.

So perhaps it would be better if I state my point-of-view:

Your equation (which is very elegant, congratulations!):
G = (S*(L-O)*(g*s+l*o)+L*(O-S)*(g*l+o*s)+O*(S-L)*(g*o+s*l))/
((L-O)*(g*s+l*o)+ (O-S)*(g*l+o*s) + (S-L)*(g*o+s*l)),
is, at its essence, a function of G in terms of 7 variables, those variables being: s, o, l, S, O, L, and g.

The well-known 3-term error model for one-port calibration consists of 4 equations (equations 1, 5, 6, and 7 here: )
Note that when equations 5, 6, and 7 are inserted into equation 1, the result is a function of G in terms of 7 variables. And those seven variables are the same as your equations's seven variables: s, o, l, S, O, L, and g.

If you then assign values to s, o, l, S, O, L, and g, and solve either your equation or the equations that represent the 3-term error model, you will get the *same* answer for G.
See: /g/nanovna-users/message/8569

So -- we have the same input variables, and we have the same result. This implies, to me, that your equation and the equations representing the 3-term error model are functionally equivalent. My guess is, some smart person (not me) could take the equations that represent the 3-term error model and manipulate them so that the resulting equation is equivalent to your equation.

When you mention "expressions which are consequences of this very net linear S-parameter model", and then you state that, because of this S-parameter model, "you have not get rid off the Core Uncertainty of the Measurement still existing : (a) in your Standards, as well as (b) in the inaccuracy of your VNA readings", I become confused. Are you stating that the 3-term error model has uncertainties and inaccuracies that your equation does not have?

I'll point out again -- both your equation and the 3-term error model use exactly the same variables, and both generate exactly the same result when values are substituted for those variables.

Therefore, to my mind, both your equation and the 3-term error model's equations must have exactly the same uncertainties and inaccuracies.

Anyway, after all that said, may we ask you now, please:

- Do you ever wondered why your VNA still leaves this Absurdness available to
its user ?

My apologies, gin&pez, but I do not know what absurdity you are referring to.

- Do you ever wondered how its measurement is finally extracted to be
presented to the user ?

If you are asking me if I know how my VNA calculates S11, the answer is yes.

Best regards,

- Jeff, k6jca

Alan,
THANK YOU, I have to re-read and save this and give it a whirl to understand it better. I’m a visual guy, so I have to see it before I can understand and believe it...

My interest is mainly in Marine VHF antenna’s, almost all of which come with a hardwired length of cable to avoid connectors being subjected to salt water/elements in the marine environment. So this is going to be standard setup fair for me. ;-)

————
Regards,
Chris

Thanks for the tip, Harold. I shall have a look. Based on the quality of
the Smith Chart treatment, they must be excellent. Just hope others take
advantage. Have a read of my QRZ page to find out what I'm all about. I
get a lot of satisfaction working technical and teaching with the HS
students at Berthoud, Co., HS

Dave - W?LEV

--

*Dave - W?LEV*
*Just Let Darwin Work*
*Just Think*

#106": More On The Fourth Load VNA Trick

@Jeff Anderson - 4 January 2020 - /g/nanovna-users/message/9158

Dear Jeff,

Thank you very much for your most valuable information, by which you declare that
your VNA introduces, to the linear S-parameter equations model, * a d d i t i o n a l *
mathematical expressions, by which it tries to express the "physical impairments"
of the Standards.

This simply means to us that your particular VNA recognizes the most obvious fact:

"The Names of the Standards - that is their Nominal Values (-1, 0, 1) in accordance to
(S, L, O) order - do not express their values".

Thank you very much, indeed !

Because, this is exactly what we are trying to say in this Group from the very beginning.

After that said, also allow us, please, to consider now that our way to use this mathematical
model, that is * w i t h o u t * the introduction of additional mathematical expressions, is by
this very fact the most simple way to confront with this really existing issue - which by way,
it also covers the non-default operation of your VNA - simply because our way covers
the measurements by * a n y * VNA.

And at this very point also allow us, please, to emphatically declare that we don't find
anything erroneous in our point of view, that is the one From A Common User Point of
View FACUPOV, since we already looked ahead to exclude VNA cases in which this
default operation it is not their default. Our claim still holds for all those still existing
VNAs which do consider by default such an Absurdness.

Finally, allow us, please, to also emphatically say that * I F * after all that provisions of
your VNA, the unknown load value is still * c o m p u t e d * using the expressions which
are consequences of this very net linear S-parameter model, * T H E N * you have not
get rid off the Core Uncertainty of the Measurement still existing : (a) in your Standards,
as well as (b) in the inaccuracy of your VNA readings.

And it is still there, because it is * i n s e p a r a b l y * associated * w i t h * the
mathematical model in use itself.

That's all the crystal clear truth.

Anyway, after all that said, may we ask you now, please:

- Do you ever wondered why your VNA still leaves this Absurdness available to its user ?

- Do you ever wondered how its measurement is finally extracted to be presented to the user ?

With our best regards,

gin&pez@arg

On Thu, Jan 2, 2020 at 09:08 PM, David Eckhardt wrote:

Thanks, Dave!
If you remove the filename from that link, e.g., , there's an index of over 300 RF engineering course files there! I collected them all... :-)
--KV5R

Something is escaping me... there are a few reports of persons that are able to run nanovna-saver under Windows XP SP3 (as I have).
But the API in kernel32 that the program complains to be unable to find, was introduced in Windows Vista and it is rightfully absent in XP....
Additionally, when started from a DOS box, I receive this message :

Error loading Python DLL 'M:\Temp\_MEI30322\python37.dll
LoadLibrary: The specified procedure could not be found.

Now, going to the Python Web pages, it is clearly stated that Python 3.7 DOES NOT run under Windows XP....
Confused....

Alberto

On Sat, Jan 4, 2020 at 01:33 PM, gin&pez@arg wrote:

Hi gin&pez

"
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

Thank you for the clarification.

I am curious why you make this claim (a), because, in my experience, it is not correct. I offer as evidence any number of VNAs (or VNA software) that allow the user to characterize the three standards in terms of their actual physical characteristics (delay, loss, mismatch, and actual impedances (e.g. as a function of fringe capacitance, etc.).

For example, my 8753C does not "consider by default" that the Reflection Coefficients of any SOL standards are (-1, 1, 0). It actually considers *all* standards to have physical impairments that keep them from being the ideal (-1,1,0). And the only way to make the VNA use Reflection Coefficients that are (-1,1,0) is to go through the rather painful process of manually setting to zero (via the 8753C's menu system) each of the impairments for each of the SOL standards that have been pre-programmed (by HP) into the VNA.

"
Does it have an enough crystal clear meaning now?

It is much clearer! Many thanks.

- Jeff, k6jca

@Gary O’Neil, N3GO
/g/nanovna-users/message/9132

Dear Gary,

Well, allow us, please, to remind you that we would not arrive at this
- most spectacular, indeed ! - conclusion, if you did not insist to ask
all those questions, while the only thing we asked from you it was to
be staying tuned...

Kind regards,

gin&pez@arg

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