开云体育

Here's the pdf:

はぁ (ha), that did the trick. I did the surgery on only one leg so there is still some imbalance, but the directivity improved from 8dB to 16dB, on par with the performance with tuning (see attached). Don't think I'll ever convince TOKO or mini-circuits to build baluns vertically like this though, and it won't fit in the shield can anymore, so I think the tuning will stay for now.

On Mon, 6 Jan 2020 at 00:28, Robin Midgett <K4IDC@...> wrote:

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?

VNA measurements require phase stables cables. The ones I use for microwave
use (upto 26.5 GHz) are 24” long and cost $5000 a pair.

The changes in phase you will observe with very long cables is going to be
much higher than short cables of the same quality. Flexing, temperature
changes are really going to screw you up with long cables.

When I do critical measurements I try to eliminate cables completely.
Measurements of my VNA calibration standards sold in kits are made

There are some ways to test cables for their suitability for VNA use. I
will add some details later on my website under the FAQ section.



There are other issues too, but they might not be relevant on the NanoVNA.
As the frequency of the source is swept, the detector looks for that
frequency. If there’s a very long cable, by the time the reflection is seen
back at the VNA, the source has changed frequency and its detector is then
looking for higher frequency than what it receives.

The solution on some VNAs is to slow the sweep speed down. Since the
NanoVNA does sweep that fast, it is unlikely to be the problem. Reducing
the span to the absolute minimum you can get away with might help, as the
frequency shift between each point will be much lower.

What’s the temperature stability of your load like? If you take a load from
room temperature and change its temperature much, it is likely to change in
value.

I have ideas, but I don't want to sway anyone's opinion..

I wonder if any of your ideas are the same as mine!

Dave, G8WRB.


--
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

Hi Peter,

go to my website and read more about this topic (ha3hz.hu)

73, Gyula HA3HZ

Hi Gabriel,

As an experiment, you could try to make a more symmetrical balun by placing the core vertically over the pcb and making sure the wires have equal length. Another request, could you publish the schematics in pdf? I'd like to study them and give some feedback. I don't use gEDA, I stick with KiCAD, Pulsonix, Ultiboard and Altium.
Happy 2020!, Reinier

Op 6-1-2020 om 08:40 schreef Gabriel Tenma White:

From: Robin Midgett

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..

Attachments:
350_ coax with dummy load.png: /g/nanovna-users/attachment/9185/0
==============================

Robin,

You might try a TDR plot and see whether there is an obvious discontinuity?

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

For an N connector, the seller must have an adapter option with a calibration kit.
My counterpart. It is very convenient to work. And the BNC option should be similar.
It solves many technological problems in production. (Apologies for bad English from Uncle Gogl.)

Please forgive me for using Chinese reply.
请原谅我直接使用中文回复。GD32F303更便宜的价格和更高的运行速度真的很吸引人，但是我们还是选择了社区更加熟悉的STM32F303CCT6，得益于高桥先生centsdr项目上stm32f303的应用，AA6KL 很快完成了STM32F303CCT6的移植，与当前版本的nanovna保持了高度的软件兼容性，用户甚至可以在当前的电路板上通过简单的修改使用新的MCU和4寸的液晶屏，这正是这个社区需要的。我们都有自己的工作，仅在业余时间开发，移植新MCU需要更多的精力，即使当前STM32F303CCT6版本也还不完善，选择一个社区更加熟悉的MCU可以吸引更多的爱好者。
您的厂础础项目是一个非常了不起的项目，应该会颠覆很多人之前的对成本和性能的看法。正如别诲测555最初发布狈补苍辞痴狈础时候那样希望通过这个项目吸引更多的年轻人关注射频，也广大爱好者提供更加实用的工具。
AA6KL 正在进一步完善它的开发，采用STM32F303CCT6和4英寸显示器的NanoVNA-H很快会推出，希望社区能有更多的爱好者参与。

胡根

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