开云体育

My FCU refuses to honor charges on my card to Aliexpress. I no longer
tempt ordering from them. Three times. Same results. Likely due to
Chinese vender?

Dave - W?LEV

--

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

After using the original with the 2.8" screen, I'm looking to order the
4.3" unit. As best I can gather, there are three units available all with
different external presentations. These are:

1) NANOVNA-F along the bottom right with the Gecko to the right of
the screen on the vertical member.
2) NANOVNA-F along the bottom right with no Gecko.
3) NANOVNA-F along the side to the right of the screen - no Gecko..

I don't want a Chinese clone. Which of these three are legitimate and
worth spending my $$ on? I do NOT want to support the cloners!


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

ive found a screen the same as hermans 3.2 inch on aliexpress(thanks for the link herman),however it goes ok trying to buy it untill i enter my post code,it just says its in the wrong format,ive tried every which way with no luck,im tearing my hair out,anyone any idea whats going wrong?,cheers .

Hi,
Like others, I am having problems with Python PyQt5 etc. I am trying to get NanoVNA to run with a Raspberry Pi 4 with very little success. Works perfect on the Mac Pro. Do you or others know of a work around for this excellent program to work on this platform? Any advice would be much appreciated.
73
G8ORE

Garry,

Thanks, I may have formulated unclear but what you state is what I meant.
Uncertainties in M act as "error bars" making it uncertain where you are in the graph, Uncertainties in the calibration standards cause left/right shifts/compression/decompression in the positioning of the graph
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NanoVNA Wiki: /g/nanovna-users/wiki/home
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Erik, PD0EK

Erik;

My bad...I incorrectly stated that zero reactance is established at all three calibration points. Everything goes to infinity at the right edge of the chart. :-)

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73

Gary, N3GO

Hello again Erik;

I think you may be confusing the uncertainty in M with the uncertainty in the calibration standard. For example; if the calibration standard is 45 ohms (a substantial 10 percent error), Only the value of Z0 changes in your equation. However; calibration of the VNA with this standard (uncorrected) equates the value of Z0 to 45 ohms, but declares it to be 50 ohms. "IF" there are "NO" other sources of uncertainty in our measurement, this would force a 5 ohms real uncertainty in our measurement results. The mathematical (and graphical) consequence of this (now hidden) error is that it shortens (compresses) the length of the perfectly linear distance to the right from 50 to infinity by 5 units, the entire length which then gets normalized to the length of 1, such that all values remain inside the boundary of the Smith Chart. Conversely; it also lengthens (stretches) the the line representing the perfectly linear distance to the left from 50 to 1/infinity (zero).

Because we have decided that there are no other uncertainties in the measurement, we get a clear picture of the consequence of the 5 ohms of uncertainty as we move away from the center of the chart, and reveal that the uncertainty asymptotically approaches zero as we move toward the outside edge. Hence; it is my assertion that the consequence of errors in the load standard are most relevant and arguably critical for measurements of an impedance at or near Z0.

In an analogous manner, I might even argue that reactance uncertainties may have even less influence on measurements of DUTs exhibiting a real part less of less than Z0; since Zero reactance is established at all three calibration points.

In a practical sense, and given that even DIY calibration standards of high quality are not difficult to manufacture; it would appear that frequency accuracy and the precise definition of the reference plane are perhaps the most sensitive, and thus the most critical calibration parameters to be controlled. Ironically; uncertainties in those parameters diminish as impedance approaches Z0. What also becomes evident from these assertions is that the quality of the standards with respect to establishing the measurement reference plane increases as frequency increases.

--
73

Gary, N3GO

As QRP RX already wrote, you need to repeat the calibration with the new reduced span to have 101 calibration points in there.

Forgive me to add something trying to create a simple mental picture of what you are saying.
As the nanoVNA has a almost perfect bridge below 300MHz (apart from a phase shift due to transmission line lengths) the relation between a measured R and the output of the bridge (M) is mathematically M=(R-Z0)/(R+Z0) and graphically (for Z0 is 50) and when only varying the real impedance of R

Am I correct to assume your conclusion can be linked to the shape of this transform?
Around Z0 the dominant factor is the placement of Z0 and the uncertainty in the measurement of M leads to a linear relation to an uncertainty in log(R) but as the first derivative of relation between R and M is at a global maximum the impact of measurement uncertainties of M is at its minimum.
For high and low values of R the opposite is true. Even the smallest uncertainty of M around +1 and -1 leads to a substantial uncertainty in R.
I assume the same is true for the imaginary component where instead of R=50 (real component of Z0) the center of the graph is around iR = i0 (imaginary component of Z0)

This then would explain why during calibration the value of the real resistance of the load and its electrical length or its reactance are important to determine the center of the graph and the uncertainty in the center and the open and short for determining the extremes and the related uncertainties there.
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Erik, PD0EK

GIN&PEZ;

I have only advanced in my understanding to the extent that I have been able to confirm that the results of complex load measurements using the G-mini equations map virtually 1:1 to those obtained from and computed by the stand-alone NanoVNA. I have not looked at, nor have I attempted to identify and compare differences between the computational processes used to arrive at their respective results.

To obtain the confirmation, required that I perform a single calibration of my NanoVNA using my imperfect set of calibration standards, immediately followed by a single sweep of my DUT*. This exercise yielded a calibrated NanoVNA measurement of my DUT and the set of the 4 raw data files (S, O, L , and DUT) that the NanoVNA used to compute its results, plus the NanoVNA's internally computed results that resulted from those same raw data measurements. All of the above were exported into a spreadsheet where using the G-mini equations I computed a new set of results which I could then compare with those produced by the NanoVNA.

I have done a limited amount of "what-if" experiments to emulate a crude but viable simulated differential analysis, but only to the extent that I was able to confirm that such testing can be performed in a quantifiable manner.

For example; I made the observation that the load value is a single interpolated data point along a logarithmic line that extends from 0 to infinity, and concluded that the accuracy of all measurements made with respect to this single fixed data point are highly dependent on the accuracy of the data point itself. It also appeared obvious (perhaps only to me) that the severity of the inaccuracy in the placement of this single calibrated data point is most critical, and possibly only critical in the immediate vicinity of the data point itself; observing that the extrapolated influence of the absolute error in the load standard compresses in significance as distance from the center of the chart increases. It seems intuitive that the ability to resolve any load standard error contribution erodes rapidly with distance from Z0, and the contribution of other uncertainties (linearity, noise, resolution in the vicinity of the measurement, etc.) would rapidly dominate elsewhere.

I have however only confirmed that the measurements near the value of the load standard being used (Z0) are highly sensitive to differential values (alternative loads) in close proximity to Z0, and the errors do not appear to propagate sufficiently to degrade the DUT measurement results noticeably. More exhaustive testing is required to perform this test in a satisfactorily convincing manner to yield quantifiable results, but I am severely limited in my ability to do so with the instrumentation I have on hand. My hope is that those with capabilities such as near perfect standards, calibrated reference impedance standards, and/or a very well balanced HW bridge are eavesdropping and gaining in their own understanding of what you are doing; and that they will eventually become motivated to chime in and contribute to this exercise.

Whatever the outcome; my ability to contribute is going to be limited to reproducing results that become useful and meaningful FACUPOV. :-)




* The DUT used in my measurements is a 7 foot length of foam RG8X coaxial cable terminated in a 1/10 Watt 3.3 ohms metal film resistor, and yields an approximately 15:1 VSWR collapsing spiral vs. frequency.



--
73

Gary, N3GO

Probably should add Python to the mix as candidate for your own application development..

Matlab is gold standard for college academics but it is more targeted at nuts and bolts simulations. It is expensive and has significant learning curve.

Octave is a great open source Matlab look alike. Most Matlab programs can be run with Octave. Octave has extension libraries for signal processing similar to Matlab. With relatively minor syntax items, a Matlab programmer can ensure their program will run in Octave.

Python was originally used often for test systems, the same group using Labview. It is very well supported open source and is one of the fastest growing programming application. If you plan on playing with Raspberry Pie you will likely be using Python.

#82' : On The Two-Port Sine Qua Non Practical Application - Source and Load
-
REF : 11 December 2019 - /g/nanovna-users/message/8136

Hello,

Allow us, please, to announce that we just uploaded an updated version at:



with slight modifications and added * e x p l a n a t i o n s * on the text.

Sincerely,

gin&pez@arg

:82'

Which had portions derived from a Project STM32-SDR which was developed by
Charlee Hill W5BAA, John Fisher K5JHF, Milt Cram W8NUE and Dave Miller
VE7PKE/VE7HR. The software was released as open source.
The STM32/SDR project has morphed to the IQ32 which is still in production.
Charlie and Milt over the years have created some wonderful things.

Dave
VE7HR


On Wed, Dec 11, 2019 at 12:53 PM Joe St. Clair AF5MH <saintc@...>
wrote:

I think the Texas hams Larry is referring to are Milt Cram (W8NUE) and
Kees Talen (K5BCQ) who once offered the AQRP Vector Impedance Analyzer kit.
The last time I looked that kit was no longer available.

--
72 de Dave
VE7HR

I think the Texas hams Larry is referring to are Milt Cram (W8NUE) and Kees Talen (K5BCQ) who once offered the AQRP Vector Impedance Analyzer kit. The last time I looked that kit was no longer available.

Hello,

This email message is a notification to let you know that the following files have been updated in the Files area of the [email protected] group.

• /NanoVNA_Console_Commands_Dec 9-19.pdf

Uploaded By: Larry Rothman <nlroth@...>

Description:
This is the latest update of the Console Commands for the NanoVNA as of Dec 9th. It replaces the previous version. updated some command descriptions (per QRP's new v0.4.3 F/W) Please let me know of any errors or omissions.

Cheers,
The Groups.io Team

Hello,

This email message is a notification to let you know that the following files have been updated in the Files area of the [email protected] group.

• /NanoVNA-User-Guide-English-reformat-Dec 9-19.pdf

Uploaded By: Larry Rothman <nlroth@...>

Description:
This is a translated, reformatted and edited version of cho45's excellent NanoVNA User Guide. The document is 37 pages and is formatted for printing. Updated Dec 9-2019 - Added new section on Developer Extended Features, general updates.

Cheers,
The Groups.io Team

Gary,

Indeed, the model is precise, and its uncertainty is only based on uncertainty in the measurement of the 3 calibration standards and (this is not stated in their formula's but I assume the extent to which the standards are known . It is stated that G = -1,0,+1 but how about uncertainties in these? Not calibration set is perfect.)
This model allows the analysis of the impact of each uncertainty separate so you can compare calibration standard uncertainty with measurement uncertainty impact.
The derived equations are as far as I can see (but I am no expert) the same as what you get when you ask Maxima to solve the 3 calibration equations for G = -1,0,+1 . Or have they been able to get a additional level of complexity reduction?
Do you already understand to what extent the uncertainty boundary calculations are different from a differential analysis w.r.t o,s and l? Any higher order terms included?
Very interested to see the real test case data. With a very well balanced HW bridge a VNA will get almost perfect o,s and l data and that will imply the calibration uncertainties and measurement uncertainties both have a lineair impact going through a mobius transform.
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Erik, PD0EK

Hello again Erik;

I think you are close but not quite precise in your understanding. Or possibly I’m not yet precise in my own. :-)

All uncertainties are embedded in the model as they are uncertain entities that exist in any measurement. There is no attempt here to sort out the uncertainties, much less in any precise manner. The equations are only a compact (minimized) set required to compute the one and/or two port results while attempting to not degrade the integrity of the calculations resulting from mathematical manipulation.

Measurement accuracy is influenced by the known inaccuracies of the standards used, but not defined by them. The true accuracy in the measurement is bounded by the collective contributions of all uncertainties in the measurement, and not simply (and incorrectly) allocated the preciseness of the standards alone.

The uncertainties in the results achieved by the equations are acknowledged; but addressed as an independent and separate but parallel computational process. This is described in terms of a mechanical (graphical) construction of the bounded limits of regions and intervals surrounding each data point independently. The limits used in describing the uncertainty boundaries are user defined, easily or conveniently determined, and are as precise as the user determines to be justifiable. The construction process is illustrated in the animated videos posted in msg # 7235, and articulated in detail in the series of 5 white papers posted at the beginning of this thread. I have only skimmed over these to date, but I believe them to be complete as presented.

I believe the equations derived thus far in this thread are intended to stand on their own as maximally efficient algorithms for both one and two port S-parameter measurements.

The Uncertainty boundary calculations are a second proposed contribution that attempts to bound the region about each measured value to the most relevant and unavoidable real constraints that have the potential of modulating the measurements away from their true and precisely accurate values. These results would be the ones used to define design margins needed to specify limits of guaranteed performance.

My expectation is to discover that the use of expensive characterized standards versus a well designed and fabricated set of nominal standards contribute only minimally toward the achievement of maximally accurate VNA measurements. At the very least, I anticipate this learning exercise to provide clarity with respect to the sensitivity of uncertainties that can be defined and user constrained or controlled.

This has not been a fast paced learning process as much of the material is quite new to me, and I offer my description of this for your consideration in your own pursuit of understanding. On any aspect other than the derivation and verification of the G-min equation, I remain a student of this process.

--
73

Gary, N3GO

Greetings Thomas,
Your best solution for a low-cost scanner is the RTL-SDR dongle, and some scanning software.
The best one (currently) is the RTL-SDR.COM V3, ($23) which has a very good TCXO, software-switchable direct-sampling mode (for freq range DC- 25MHz), input protection (diodes), aluminum case, and SMA input. It will receive in bandwidths up to about 2.56MHz, and there is software that'll step it along, so you can cover a sweep from 25-1800MHz pretty fast.
The only down-side is that rtl-sdr dongles have no bandpass filtering and will show spurious signals, so you just need to keep its RF gain set low enough that they disappear. They are greatly improved with addition of notch filters for AM and FM broadcast bands (~$10-20 each).
For (free) software, SDR# ("SDR Sharp") is probably the most popular, with many plug-ins, including a full-featured scanner plug-in. There is also software that'll step it along and generate RF heat maps.
I'm not advertising for them, but I know what works... I use mine as a "poor man's" spectrum analyzer and freq counter, and after software calibration to a freq standard, it works quite well.
Don't get a cheap plastic DVR-B dongle; they have terrible oscillator that wanders around all over the place.
73, --kv5r

Fully agree
I'm have been supporting public domain SW for more than 15 years (and still am)
The step from having some SW that is usable versus SW that is robust for any usage is rather big and requires a lot of time.
Not sure I will want to do that for all SW's I make.
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Erik, PD0EK