开云体育

Hi Jeff;

Per my post:
@ Gary O'Neil - /g/nanovna-users/message/9184

I don't find any source of disagreement in your posts:
@ Jeff Anderson - /g/nanovna-users/message/9178
@ Jeff Anderson - /g/nanovna-users/message/9181

I will also confess that I overstated a Hackborn quote which modified its more accurate interpretation. He didn't dismiss anything, but rather makes the statement that all of the errors and uncertainties in the system are measured and remembered.

By that inexcusable but excellent example of my inability to make and defend my point; I will attempt instead to understand your understanding of the process, and search for where the two will hopefully converge.

After several reads and re-reads of your and Erik's posts; I think you two may be on the same page. Your post, and another by Dr. Kirby:
@ Dr. Kirby - /g/nanovna-users/message/9183

hint at a possible disconnect in "my" understanding, which may be linked to a vagueness in the use of jargon, or more pathetically, my lack of understanding of the jargon in use.

The way I am interpreting your posts, I see the use of the terms calibration, characterization, and correction. You also identify the noise and imperfect characterizations of the standards as not being corrected by the error correction process.... referring to a Hand quote.

You also make reference to HP and Keysight quotes... both of which I agree with as being correct. To my point; any statement that the "accuracy" of something (anything) used for the purpose of improving the accuracy of the measurement must itself be accurate cannot be argued. It is made true by the way it is stated and/or presented.

Clearly there is no argument that even with the highest of quality in the standards, at some upper limit of frequency, the manufacture of standards sets to the exacting dimensional tolerances required to guarantee that the reference plane remains constant becomes unachievable, significant rotational errors occur and corrections for the known and well defined imperfections are needed in the calibration in order to make meaningfully accurate measurements.

So my lack of understanding seems to lie in the question being what's the point of attempting to model imperfect standards of uncertain accuracy, and using that model to corrupt the ability of the algorithm to accurately measure and remember all of the system errors and uncertainties with uncertain guesses at what the ones that are measured have been characterized to be? Are not the errors that manifest themselves as problematic, only problematic because they result from differences in the location of their respective reference planes? the uncertainties of the parasitic reactance properties associated with each of the standards are measurable, and thus they will be "measured and remembered". As such, they are all present and accounted for in the calibration. Characterization of the standard reference plane location (degrees per GHz) would seem to be a more precise and accurate manner to compensate (not calibrate) for their respective rotational offsets without compromising the integrity of the calibration algorithm. After that; how precise does the rotational compensation need to be in order to sufficiently orient the regions of infinity to the VNA user such they are presented with the most accurate measurement the VNA is capable of providing?

This brings up yet another question. If the devices are "measured and remembered" as the math clearly dictates, what would cause a short and an open (defined as such) to appear anywhere other than the locations -1 and 1 without biasing the algorithm to place them differently? If they are intentionally placed at a different location, what is the justification for doing so, since this would seem to create a need to compensate for the induced post calibration offset errors ?


--
73

Gary, N3GO

Thanks Dave, I'll try that soon..hopefully tomorrow evening.

Hi Clyde,
Thanks for the quick response.
Here's a plot of the dummy load across the same span....looks good to me, but I'm here to learn from others.
I haven't tried VNA Saver yet...would have to spend some time on that; hopefully this week.

Thanks for the follow-up Chris. I ordered on Friday and pretty much followed the same procedure although I have not communicated with her since I sent the payment because they were already well into the weekend at that point. I chose the DHL shipping option so I hope to see some sort of tracking info tomorrow.

Port 00 or Port 01, that used for one-port measurement of s11, may not be a
good 50+j0 source over your frequency range. You exhibit everywhere better
than 15 dB return loss which is pretty good, but the periodicity of the
measurement is a bit disturbing.

Try recalibrating and remeasuring with a 6 dB attenuator on the s11 port.
That will assure a return loss in excess of 12 dB and stabilize the
impedance of that port.

Dave - W?LEV

--

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

On Tue, Dec 31, 2019 at 08:52 AM, W0PWE wrote:

Chris - Did you actually order the NanoVNA on the Alibaba site or did you do
it all in e-mail with Maggie? I have contacted her via e-mail so all is good.
I just need to know what the process is. Thanks - Jerry

Sorry, didn’t notice your question till now. I started a chat with “Maggie King” on the Alibaba site via hugans store on their. I simply let her know I would only purchase via a paypal payment. She gave me the paypal account to send the money to ($50 for NanoVNA-h with PCB 3.4 + $10 DHL shipping), I sent it via paypal and notified her on the chat. She said got it, and I hope to receive it soon. ;-))

--
Regards,
Chris

Additional info...it's a piece of 1.25" hardline, and the response is much worse going up in frequency; ~-5 return loss at 146 MHz.

On Sun, Jan 5, 2020 at 11:22 AM, <nanovnagroup@...> wrote:

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.

I’ve had the EXACT opposite experience. I’m not a prime member on Amazon, and m,ost of my deliveries are delivered in 1 to 2 days, with free shipping (because I simply place orders over $25. If I buy a $10 item, I put it in the cart and wait a few days until I need something else that puts me over 25. I get an amazon delivery about 2 or 3 times a week. I have never in 15 years, had an issue with any order. And the few that I wanted to return(didn’t fit or I just didn’t like the quality..), were returned for free with free return shipping, and no questions asked. “On eBay, I have had to BEG companies/sellers to accept a return, have to pay the return. Shipping, often also a return fee, and I’ve had 5 or 10 instances over the last 15 years or so they just failed to accept a return even though there add states they accept returns. The only re-course is bad feedback, which is almost useless.

When you purchase on amazon, YOU decide which sellers you purchase from, OR you let Amazon decide. That could be what you are doing wrong, and why you report amazon sending you their choice of product. If you click on the sellers list, you can choose which one you wish to use.

Believe it or not, I’m not a big fan of the whole “Amazon” thing, mainly because I don’t like they way they are killing main-street and the brick and mortar stores. But having said that, you can not beat the “amazon experience”.

--
Regards,
Chris

Most rf lines like low density foam has a spec return loss of about 20 db.

Did you put the load on the output of the VNA? This looks somewhat normal
but the return loss is a bit marginal. I am curious about the return loss
of the load by it self. Do you have the VNA saver program to look at the
line in the TDR format?

I've calibrated my NanoVNA & connected it to an approximate 350' length of coax with a known good dummy load on the opposite end. The S11 plot is attached...not pleasing at all.
Can anyone on the list say what the cause may be?
I have ideas, but I don't want to sway anyone's opinion..

Hello again Erik;

@ Erik... - /g/nanovna-users/message/9167

@ Erik... - /g/nanovna-users/message/9166

@ Jeff Anderson - /g/nanovna-users/message/9158


I attempted a response to the above referenced posts, but terminated it because I find nothing in your comments, nor Jeff's that I take issue with. Your most recent post describing modification of the NanoVNA's bridge to accommodate different choices for Z0 in fact convinces me that you do have sufficient insight to grasp the point they have been trying to make; and neither they nor myself have been successful at communicating it.

What there research provides, and where the focus needs to be pointed is not the measurements themselves, nor how the measurements are made, nor whether or not the user desires to obtain or otherwise characterize the standards used for calibration in order to obtain ultimate measurement accuracy.

The research they've done does however provide the tools and insight needed to evaluate and challenge the value and utility of performing such a task. In the reflection coefficient regions of -1 and 1, independent of noise and dynamic range, the computed results are no more or no less precise, or accurate; nor is there any impact on the uncertainty in the measurements; since both fall at or very near the regional limits of infinity where magnitudes of error in the computed impedance values can occur without consequence in an application, no noticable relocation of the plotted response. Rotational errors result from incorrectly identifying the location of the reference plane, and these can be easily identified and compensated for.

The purpose of the experiment of using the gross difference in calibration loads was not intended to highlight the VNA's utility, but rather to demonstrate that even gross errors in load calibration (4:1 and 10:1), do not make the measured results any more or less accurate, so long as the value at Z0 is well defined.

As regards using the VNA at a Z0 of 5k, your comments are spot on... Hence; I know you fully understand this point. It may however remain quite usable in spite of the increase in noise floor, but accuracy in the measurements will be no more or no less impaired as dictated by the accuracy of the load standard definition, and the tolerable uncertainty of the increase in noise.

For example when calibrated with 500 ohms, my 50 ohm standard resolved to 4.7 to 4.95 ohms without averaging. Considering this is a measurement made in 10:1 mismatch environment using an uncharacterized load standard of nominal value, this is a respectable tolerance; and one I would consider quite adequate for most applications that I would consider.

Consider also that any standard used at any frequency intended to serve as a zero ohms "standard" is quite likely closer to or, at the very least, as close as any product manufactured with the intention of zero ohms being a measurement region of great scrutiny or interest. Of course the same consideration would apply to the open standard definition as well.

Consider also that purchasing well characterized standard sets places your confidence in the uncertain but much improved accuracy of your results in the uncertain but reliable judgement of a third party, at a necessary but painful increase in cost; while allowing you to maintain the same degree of uncertainty in the accuracy of your measurements that you started with... at minimal risk.

--
73

Gary, N3GO

On Sun, 5 Jan 2020 at 21:58, Jeff Anderson <jca1955@...> wrote:

In other words, do NOT use (-1,1,0) as your SOL characterizations.
Instead, use the standards' actual characterizations.


- Jeff, k6jca

I just see your comment, and since I happened to have a VNA calibrated, I
stuck an Agilent short from an 85052B 26.5 GHz 3.5 mm calibration kit on
the test port via a special adapter needed for this. As you can see on the
Smith Chart, the arc starts at the far left (short) and is becoming close
to the right (an open) by 7 GHz.

The VNA was only calibrated to 7 GHz and I could not be bothered to
calibrate it again, but the phase at 7 GHz is about 19 degrees, so I expect
by 8 GHz or so the phase would be a text-book “open” despite it would read
zero ohms if measured on a multimeter.

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

Thank you Luc, very helpful!
Randy
NC8U

On Sun, Jan 5, 2020 at 11:28 AM, Jeff Anderson wrote:

. (And B. P. Hand recognizes this in the Feb 1970 issue of the HP Journal when
he states that imperfect characterizations of the standards are one of the
sources of error.)

A slight clarification -- Hand was referring to errors that were *not* corrected with the error correction process. Noise is one of those errors. Imperfect characterizations of the standards are another. []


Here are some other quotes regarding the importance of the accurate characterization of standards...

From HP's 8753D User's Guide [], Page 6-50: "When you use a measurement calibration, the dynamic range and accuracy of the measurement are limited only by system noise and stability, connector repeatability, and the accuracy to which the characteristics of the calibration standards are known."

Note that last clause: "the accuracy to which the characteristics of the calibration standards are known." In other words, the more accurately known the characteristics of the standards used for the calibration process are, the more accurate will be the measurements.


From Keysight, "Specifying Calibration Standards and Kits for Keysight Vector Network Analyzers []: "The accuracy of subsequent device measurements depends on the accuracy and stability of the test equipment, the accuracy of the calibration standard model, and the calibration method used in conjunction with the error correction model."

Note that "the accuracy of the calibration standard model" is one of the factors determining the accuracy of measurements.


From Mini-circuits App Note AN49-017 []: "Approximating SOL standards by their canonical/ideal reflection coefficients will undoubtedly incur significant inaccuracies in phase measurements as the phase cannot be treated as static due to the ‘line’ in the transmission line model"

In other words, do NOT use (-1,1,0) as your SOL characterizations. Instead, use the standards' actual characterizations.


- Jeff, k6jca

I cant upgrade my VNA-H FW 0.2.3-2 20191018 with new releases after October 2019 with DFuSe 3.0,6 from Google disk by two reasons: Have got Upgrade successfully with NanoVNA-H_20191125.dfu, but old version still remain innanoVNA.Verify was OK,Upgrade OK....but nothing happens in VNA,
Second reason:
I do not dare to continue after Verify due to --> got Error :File difference at address
0x08000001 -File byte is 0x04 Read byte is 0x02. This happens with several releases on same place 0x08000001 and file byte and read byte are different with different releases(for example - 0x0D and 0x051).
Have made copy of mine FW 0.2.3-2 20191019 with DFuSe -No errors after Verify !
Any Help will be appreciated.
Peter/Lz2pg

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

Hi Gary,

"It is unbelievably 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."

For the vast majority of VNAs, the above statement is simply *not* true. In fact, for *any* VNA (or VNA Software, such as NanoVNA-Saver) that allows you to define the impedance and delay characteristics of the SOL standards, improving the (verifiable) accuracy of these characteristics then programming those characteristics into the VNA will enhance the accuracy of the final result.

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

Not true for the vast majority of VNA's or VNA software that allow the user to input the non-ideal characteristics of the standards.

After calibration, the S and O points are not plotted as "ideal" (i.e. -1, 1), but instead plotted per their *actual* impedance and/or delay. For example, a "short" that has been characterized to have delay will not plot as a point but as an clockwise arc on the unit circle, starting at 9 o'clock.

(The "L" standard, being the 50 ohm load, is a special case and plotted as a point at the center, but this is because, by convention, the typical VNA Load Standard is assumed to have the same resistance as the system's characteristic impedance, e.g. 50 ohms, which is why it is important to have the Load standard be as close to 50 ohms as possible, unless your particular VNA (or VNA software) allows you to set this to a different value).

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. :-)

Are you saying that the requirement for precision calibration standards, as part of the correction process, was *dismissed* in '68? If so, I believe this is not correct.

HP (with its employees Hackborn, Hand, Rytting, and others) created a VNA error-correction technique that, by measuring a VNA's errors using SOL standards with **precisely known characteristics**, can give accurate S11 measurement results. And the more accurately the standards' characterizations are defined to be, the more accurate will be the calculation of the inherent VNA system errors, resulting in more precise results, after these errors have been corrected out of the measurement. The requirement for precisely-defined calibration standards was *never* dismissed. (And B. P. Hand recognizes this in the Feb 1970 issue of the HP Journal when he states that imperfect characterizations of the standards are one of the sources of error.)

The simple fact is -- assuming you can program into your VNA the known electrical characteristics of your standards (delay, loss, Z, etc.), then the more precisely you can define these characteristics to be, the more accurate will be your final results.

For those VNA's that do *not* allow one to input the physical characteristics of your standards (e.g. the NanoVNA running stand-alone), the user should try to ensure that the characteristics of the standards used for calibration are as close to the internal definitions used by that VNA . For the NanoVNA this is an open with no delay and fringe capacitance of 50 fF, the short is a perfect short, and the load is a perfect 50 ohm load. Or use external software (e.g. NanoVNA-Saver) that allows the user to enter into the software the actual characteristics of the standards.

- Jeff, k6jca

Thanks Luc for taking the time to write and translate this document. Very well done...

Roger

From: KV5R

On Sun, Jan 5, 2020 at 02:24 AM, David J Taylor wrote:

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

Umm, I love to, but no... U.Kansas makes them publicly available (not restricted to student accounts), but re-packaging and posting them, without written permission, would not be appropriate or legal.
73, --KV5R
================================

Understood, thanks!

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

Where do you want the radiation to go?

Biquads typically have strongest pattern broadside to the bowtie. Mounted flat on the ceiling, that would be primarily to zenith. Are you planning to communicate with orbital satellites?

If you are looking for terrestrial communications, a wall facing your desired repeater might be more desirable. Also pay attention to the polarization of a biquad (Im fuzzy on which axis is the polarization plane for that antenna) but your application will probably want vertical polarization.

And if you want your biquad to behave as a unidirectional antenna, stand it off from a ground plane 1/4 wave. This will also increase the gain 3dB in the other direction.

73;
Bob KV4PC