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- Опубликовано: 11 июн 2024
- This video describes why a "user" calibration is needed when using a VNA (vector network analyzer), what systematic errors it corrects for, what is meant by a measurement plane or calibration plane, and finally an example of how the calibration is performed on a nanoVNA. Note from this video can be found here:
www.qsl.net/w2aew/youtube/why_... 
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Congratulations Alan for being recognized by the ARRL member spotlight in the July edition of QST. Your videos are a treasure to the hobby.
Excellent video and really covered a much better understanding how to use this little device! I was ready to send it back until I watched how to use the menu. Customer service was harder to use on Amazon than your instructions. Thank You!
This is, easily, the most elaborate Yoo-hoo commercial I’ve ever seen ;)
Alan, your articulate and thorough descriptions and demonstrations are so helpful. We owe you a debt of gratitude. Thank you.
Alan, I'm so glad you did this video, much easier than the confusing manual that comes with it, in fact I've recorded your video, on to a usb stick ,for when I forget, which is often, until it synch's with the grey matter.
73 Paul M0BSW
I don't think I got a manual. I just got mine and I am learning by doing and watching videos.
Clear and to the point. No chatter or background noise. And I mean the speaker not the actual background. You and Mr Carlson are probably the best at getting info across for listeners that want just info and no junk. Thanks.
As a metrologist engineer in the VNA department of the VNIIFTRI, I think it will be useful to add some information for those who don't own NanoVNA yet. The main drawback of this device is that it has only 101 measuring points. It means that if one wants to scan, let's say, G5RV antenna over 3 HF bands from 7 to 21 MHz, the span between two adjacent measuring points will be 144-145 kHz. It is definitely a too wide frequency step to get at least any reliable measurements. In fact, 101 points are enough to sweep antenna over any 1 band no matter HF, VHF, or UHF. Another (practically small) drawback is that the test signal on lower frequencies is not a sinewave so if the device under test has resonances on harmonic frequencies it can influence the measurements.
As for me, I'd like to have an opportunity to define calibration kits for NanoVNA fore some extra precision, but to be honest, there are too many other sources of uncertainties, and even if I will calibrate NanoVNA using Keysight 85052D calkit the NanoVNA will not be much more precise than it is. Of course, I can get all the possibilities I want using Chinese KC901 or Russian PLANAR VNA but the price will be refreshing. Especially knowing that more expensive "real" VNA will require phase-stable cables with metrology-class sockets and calibration kits which are nearly as expensive as gold, and it's not a joke. In my opinion, NanoVNA is the best portable amateur measuring device in its class. Devices like Arinst, EU1KY, and Sark-110 antenna analyzers provide only one-port measurements, and most of them are already more expensive. OSA-103 provides 2-port measurements but requires a laptop, case, and extra modules for frequency range above 100 MHz. The least normal VNA is times more expensive than any of those above. MEAS (Measurement Equipment Acquisition Syndrome) is a very expensive disease. :)))
The 101 measuring point limitation is easily compensated for by using the nanovna-saver software. You can specify a sequence of multiple samples within your measurement range to get more usable resolution. It also will do its own calibration based on your sweep settings (which is quite necessary, IME). You can also do averaging across multiple sweeps to get nicer representation of your results. I never use my NanoVNA's built-in interface if a computer is nearby.
Why Rant about comparing it to professional devices that cost many thousands of dollars..some people like to keep things as simple as the job it was designed to do..
Congratulations on being a Metrologist Engineer !! That's all wanted to hear.!
@@andrewverran3498 MEAS is a costly disease. :) I myself own a NanoVNA-F and am pretty happy with it.
I bought one several months ago, and now I can begin to use it properly. (Also, shout out to the notification squad;)
Me too!
Me three lol
I've looked at the schematic and was amazed how you can just repurpose a bunch of cheap ICs to make a real instrument. It has: Wien resistor bridge, 3 mixers, freq generator + LO based on a multiple-output frequency synthesizer chip, and a multiple-input stereo audio codec as a detector. The signal generator frequency if offset from LO by some audio-range frequency delta, so when they are mixed, the mixer output can be fed to the audio digitizer for further amplitude and phase analysis by the firmware in the MCU.
Not so much a Wien bridge, as a modified Wheatstone bridge. Otherwise very much agree that the nanoVNA is an amazing design.
Hey, great to see one of my favorite RUclipsrs in the latest QST magazine.
Really enjoy learning on your channel, Alan.
Keep up the good (fun) work.
I addicted to this channel. Thank you a lot. you made quarantine much meaningful.
I have measured NanoVNA Chinese calibration standards using R&S ZVA-40 in my office. It's pretty wonderful fact that these standards are pretty good in the working frequency range and even beyond 1 GHz! Although Open standard isn't a masterpiece of stability, but Short and even Matched load are usable for up to 3,5 GHz. Also NanoVNA itself had shown pretty usable stability and precision compared to ZVA-40, and this fact is absolutely wondering knowing the price of NanoVNA. As for me the most wonderful that it works well with full-size HF antennas in the city.
So glad you got one of these. I use mine quite a bit, so I'm looking forward to more videos so I can better understand it's uses.
Thank you so much for this great training videos, it helps me a lot to understand why. You are bring such stuff over to your students that I enjoy every second of learning.
Stay healthy, regards from Hannover/Germany, Helmut
Wait a minute - there was a piece of coax connecting the antenna to the VNA - so you were measuring the characteristics of the antenna and transmission line. Great video as always, thank you!
Yes, of course. But in this case, you'd also be connecting that same coax to the transceiver, so the impedance looking into the coax is what matters. If you wanted to design a matching network *at the antenna*, then you'd want to measure the impedance *at the antenna*, thus perform the calibration *at the antenna*.
@@w2aew Yes, absolutely! I was just joking, as you had explained so carefully that the part of the reason for doing a calibration was to correct the measurements to the measurement plane of the DUT - in this case an antenna. As I said, an excellent video.
@@davidv1289 Calibration to remove the effect of cables and adapters on the measurement is called "deembedding".
Very nice, straightforward explanation on how to calibrate the NanoVNA.
One addition that I think would be helpful for first timers to the NanoVNA is how to tell the difference between the Open, Short, and Load Calibration Standards provided with the unit.
Thanks, looking forward to more videos.
Ron - KJ5XX
Thank you for the video, Alan. I have one of these VNAs ordered, and on the way soon. This video certainly does help understand the operation and use of the device. 73!
Thank you sir for all your awesome videos! I have my VNA Nano on order, looking forward to playing with it!
Great explaination. Thnaks for the time you took to prepare and produce such a quality video tutorial.
The probe as a pointer always cracks me up
Thank you very much, sir, for explaining a very crucial concept very easily!
Great video. I have the NanoVNA-F [larger screen i believe $125] and I am enjoying learning about it's many uses. Incidentally I am learning about Smith charts now because of this device and your easy to understand videos on that topic also. Thanks and keep them coming.
Thanks Alan for the amaizing service you drop the world.
What is the name of the device where you write the schematics? What model of tablet is it?
Perefect timing, mine arrived yesterday and i ioened the oar el box tiday. So i will go through if sgep by step watching this excelkent and ooportune video !
Great job! Nano VNA or lab quality VNA both will always need calibrations. Your work is a fine example of why it's always required.
Yet another great video, you're now my #1 go to RUclipsr for all things RF. What is the tablet you've started using to do your drawings/notes?
it is from www.remarkable.com
Looks like a great little tool! I'll put it on Santa's wish list. A lot in such a small package! A lot cheaper than an antenna analyzer and WAY cheaper than $10,000 for the commercial unit. Thanks Alan!
Great work. I appreciate your ability to explain.
Thanks for another very informative video!
As always, a straight forward and easy to understand lesson. Thanks! BTW, I never use my Nano without Yoohoo either...
hey! about half a year I saw the remarkable in one of your videos ... I got one a few months later .. indeed - awesome piece of kit !
Alan
In my 50 years in Engineering I've used the HP 8410,8509,8510 and PNA -X I wish your presentation skills were available then it would have been a boon to the field . This thing intrigued me WoW I could do my FA lab work from home with this amazing device I thank you know your videos I have spread the word
Best of 73's
Bill
WB2UFC
Thank you for your kind words! 73 de Alan
@@w2aew QSL btw what model is that the v4?? Also I was intrigued by the ant tuner you used with vna what is the make and model???
Bill
@@williamstevens3029 The VNA I showed is the NanoVNA-H4, and the tuner is a Ten-Tec 238C.
Excellent video! Thanks for this information, it helps me to understand how to calibrate nanoVNA and why to make this everytime I need to use to check the SWR in other bands. 73s TI2GBB
Thanks Allen. You just cleared up a question I had in mind, whether or not to include the cable in the calibration but upon thinking about it more I remember the cable is part of the antenna.
It all depends on what you need the results for. If you need to see the impedance of the DUT itself, then cal at the DUT. If you need to see the impedance at the coax input (since it is how the DUT is used, such as an antenna), then cal at the VNA.
Thank you very much. Looking forward to upcoming VNA topics. :) Stay safe, yall!
Nice demo, I picked one up last week, am waiting for it to arrive, I have some sma antenna from China that I need to verify the actual tuned frequency for.
Nice Video as always. Thanks.
Educational TV at its best 👍
Just saw the QST member spotlight on you. Congrats!
I went through it on my machine and I got it. I still have a lot to learn on this. Like setting the frequencies.
Excellent intro and refresher Alan. I had the pleasure of attending HP Training on their top-of-the-line instruments some years ago and used their best best Network Analyzer for a year or so. But, old age and being away from Ham Radio, and RF testing in General for over 35 years has stripped my brain of the basic how-tos. I believe I'll get a NanoVNA, Just Because is't so darn cool. Even if I never get around to using it.
Regards, Don, W5MML...🤠
8:25 it's the Copen or the electrical length of the open standard (at these frequencies it just mushes together to look like a lumped element so, yes, Copen) that need to be considered and in fact put into the firmware to use the SMA standards given for an accurate cal. I'd LOVE to know how to enter other cal coeffients. It could be done off board. These are great VNAs. i have two of 'em.
Great explanation. A few minor changes, but it is still great.
Another video from the great AW :D Must be my birthday...
As always an excellent video!
Great Video! As always.
Thank you.
Awesome video Allen.
Well that was helpful... I really didn't understand what I was doing with it. Thanks!
50 bucks for a tool that's as powerful as the nano VNA was a no-brainer
Nice write up about you July issue of QST. How do I know? After years of watching your excellent videos, you inspried me to learn more about HAM radios -> ff -> got my license and joined ARRL. Qst issue comes out (which I really enjoy reading) ... rest you know. All, I can say is thank you, you are a wonderful teacher and I appreciate what you do for us.
Nice man! Side topic: I reallyyyy need one of this remarkable e-notebook, these are gorgeous for engineering drawing
They are nice, pricey - but nice.
@@w2aew Here to Brazil with taxes it will cost 8x more 🤦♀️ hehehe
Thanks Alan, excellent and informative as always. Now I know why I got different results when I changed the co-ax length on my glider antenna design. Doh!! :)
Yes - remember that changing the coax length *will* change the impedance seen by the transmitter, but it will *not* change the SWR (except in the case of adding a lot of lossy coax, where SWR will appear to get better, but really doesn't).
Helpful video. I liked it
Thank you for your videos. Would like to suggest a new video that gives insight into ESD safety.
Great video, thanks!
super cool video and VNA
Great video, thanks
To perfection. well done.
Nice article in QST!
👍Very useful video - thank you.
Thanks for this video. "summertime...(delay)...and the living is easy.....(thanks to Alan & RUclips ".
This is great - thanks - when doing the calibration, why didn't you put the cable? Isn't that necessary for the calibration process?
Great presentation! You did not mention the torque settings for the connectors at high frequency needed to reproduce measurements.
thank you great information
Excellent clip.
It would be good to be able to measure extremely low return losses like -90dB by adding LNA, PA, Directional coupler, circulator, limiter and other circuits to the VNA, without damaging VNA or making the whole thing to become an oscillator. I guess we need to design another box to VNA to do that.
I think something like this: Port 0 of VNA to PA then to circulator, forward path circulator to D.U.T. Return path to Port 0, which could cause this thing to oscillate!
I always liked your pen and paper sketches. The new e-ink notepad is nice, just going to take long-time viewers of your channel a while to adjust. 😱 change!
I wrote a series of articles on noise bridges years ago for a couple qrp publications. We've come a long way since then! Thanks for the work you put in to these videos Alan. BTW, what e-ink tablet are you using in these videos? Tnx, N8UX
Yes, we've definitely come a long way from the Noise Bridge days, and light-bulb dummy loads / tuning indicators! The e-ink tablet is from www.remarkable.com. Pricey, but very handy for creating/editing/revising my notes without using a ton of paper - and no need to scan afterwards.
Thanks for the nice video. My question is why my upper right reading on 7mhz is jumping from 7.000 to 7.230 freq. when i try to sweep the bands. Thank you
You need to mention that the calibration of Isolation and Thru and what they are used for are covered in #315. I ended up here when searching for how to calibrate but didn't discover #315 until going down the rabbit hole a while.
Great video but left me with an appetite. Would have been perfect if you went a little farther in interpreting the wave forms, especially the SWR and what a good and bad SWR looks like. But otherwise VERY informative, and looking at the title of the video, was 100% spot on (this isn't an antenna tuning video). Thank you!
TNX for another great video! Cool little pocket sized Gizmo, much easier to lug around unlike my HP-8712ES !
73 N8AUM OH, when do you get on the air ?
Thanks for sharing. Also, can you please share what the tablet device you are using to take/share your notes and diagrams?
It is from www.remarkable.com
Nice video 🖖 👍
Could you explain how is possible to receive the RF signal using a light bulb as the RX load.
I know EM waves are moving from the transmitter to the receiver generating a oscillatory current and turning on the incandescent light bulb.
Would be nice to understand how exactly it works, and demonstrate it.
Great video! Thanks. Often I need to make a connection to a PCBA to match an antenna. I can calibrate out my cable in the normal fashion; open, short, load but then need to calibrate out the "adapter" to the PCBA. I often use port extensions to do that. Is the NanoVNA capable of that? Also, I have been hooked on your videos for awhile now, have not seen them all but was wondering if you ever did a video on using port extensions and if not would you consider doing one?
Yes, the nanoVNA has a Port Extension feature. They don't call it port extension though, they call it "electrical delay". It is found under the Display>Scale menu.
Excellent video and well explained. What is that "tablet" or e-notebook you have your notes written on? It looks great.
It is from www.remarkable.com
Thanks!
I have been using vector network analyzers for many years. NanoVna is perfectly useful for amateur use for vswr measurements or for S11 parameters. For more demanding use, for example adjustment of tunable filters, its sweep is extremely slow, therefore there is no feeling of adjustment in real time, for me it is the greatest lack of NanoVNA.
On the other hand in the PC application NanoVna Saver I am surprised that it is possible to use the calibration standards for other calibration kits beyond sma kit, I have been able to check the use of a calibration kit N that has worked pretty well. There should be no problem calibrating TNC, BNC, 7/16 or any other. The only thing that you need are the parameters from the maker of the kit or modeling yourself the behaviour of your standards, that is not an easy task.
The best thing about being able to calibrate a VNA is being able to remove test leads both in reflection and transmission. It is important that the test leads are stable, otherwise the calibration will be useless, calibratión only will remove systematics errors.
To know more about this topic emlab.uiuc.edu/ece451/appnotes/Rytting_NAModels.pdf.
Thank you.
Alan, first of all, thanks for this amazing video. I have a question that I wasn't able to find in the comments. In the end of the calibration, you used some coaxial cable to measure the antena parameters, but the calibration was done without this cable. So, what is the correct calibration procedure (with or without the coaxial cable)?
Both are correct - depending on where you want the measurements to be valid. If you want to measure the input impedance of an antenna - at the antenna's input, then run the calibration at the end of the coax where the antenna is going to be connected. If you want to measure the impedance looking into the coax that feeds the antenna (where the transmitter connects), then run the calibration at the VNA port where the coax will connect.
@@w2aew Thanks Alan!
I was wondering when Alan would buy a NanoVNA and do a video on it!
Will any stylus work ? One for a computer or it has to be one for a mobile or tablet?
I want to understand and calibrate the Isolation and Thru. Do you have that video?
Fantastic video, Alan. I'm new in the RF field, so this is really valuable to me. How does the performance of the NanoVNA compare to a more traditional high-end VNA? There must be some tradeoffs there I think.
Also, are you using the calibration kit included with the NanoVNA or do you recommend replacing? Looks like the load you are using differs.
It would be really interesting to see if the nanoVNA could measure stuff other than antennas and filters. For instance plane impedance in a PCB.
It lacks speed, dynamic range and IF bandwidth adjustment. When sweeping over large bandwidths I find it easy to miss narrowband notches that fall in the gaps between measurement points. But it really is pretty good for a lot of tasks.
@@scienteer3562 cool, thanks :-)
The nanoVNA has lower dynamic range, only 101 test points (unless you use the external s/w), no IF BW adjustment, no averaging, - but - still *very* useful. I was just using the OSLT kit that came with it.
AWESOME vid.... I never heard about that. On minute 2:30.. what's that tablet..and where can I find it??? THANKS a lot my friend.. 👈🏾🎩!!!
e-ink tablet from www.remarkable.com
Thx for clear explanation , I bought the same one for quick measurement and it's great. For better measurement I have my trusty HP8714 :) hacked from HP8713B :D
Great tutorial thanks. How do you get your Blue trace to be on CH0 along with the other two that default to CH0?
Found the option sorry! To change the trace channel, select DISPLAY CHANNEL CH0 REFLECT or CH1 THROUGH.
Why would you want to display the reflection coefficient? because mostly you display the Return loss and VSWR but why the reflection coefficient?I have never used a Network Analyzer that was able to display the Smith Chart at the same time with the Return Loss and VSWR like you did in this video. HP Network analyzers in the 80's when displaying the smith chart I don't think there was a way to display the Return loss and VSWR at the same time as the smith chart. The complex impedance of the antenna is a combination of the impedance of the antenna and the Ratio of the forward wave and reflected wave?
Thanks for the video!
Would it be better to run the calibration at the end of the cable rather than directly at the nanoVNA ports so that the measurements capture as little of the additional cable length as necessary?
Sometimes it isn’t possible or convenient to calibrate at the end of the cable. Cal at the DUT end of the cable is generally only needed when you need the actual complex impedance or reflection coefficient from your DUT. Additional cable will not change the return loss or SWR, it only changes the input impedance.
Thanks for this and other nanovna videos. Is there a way to calibrate these to 75 ohms? I haven't seen anything that addresses this and it would be nice to do so as many/most of the rx only antennas and receiver connections are 75 ohms.
Everett
KE5MMT
Not sure it's really practical to do with just the nanovna. There might be PC based software that will help with this.
The lack of concentricity in the Y direction of the long open (i.e. spiral being centered perfectly) indicates the reactive portion of the cal coefficients presumed (and hey, they may be zero) are off, typically in the L coeff for the short (or the Copen for the open). Less likely at these freqs. would be the load inductance.
Thanks for that. I don't think there are any reactive components included in the cal standards on the nanoVNA - I believe they're assumed "perfect". What do you expect for $60, including the "standards". Thank you for the education on the calibration standard nuances.
@@w2aew I agree.. hah hah! I worked at Casacade Microtech for 6 years on probe development and met the zen masters of this stuff. The nano VNAs are nothing short of amazing, and you did a great job presenting them.
How do I change all the options, if they are not correct set in the nano, I'm totally beginner on this stuff.
Been doing electronics for a while, but RF has always been black magic to me. Thanks for the very helpful videos.
I'm doing my first VNA measurements (with a miniVNA Tiny) and after doing the OSL calibrations with the terminators directly on the SMA connectors of the VNA, I tried to connect a SMA to IPEX pigtail, which was then connected to a 50 Ohm load on a demo board. I was expecting to see the SWR increase, but it increased all the way to 1.92:1 at the highest point, with several "rounded" lower peaks in the entire range of 1MHz to 2.99GHz. As I have no experience in the field, I don't know if it's normal, but it seems quite high, considering both the pigtail and load should be 50 Ohm (DC resistance verified to be 50 Ohm). Can anybody shed some light on this?
Good video, thanks. But at what frequency does measurement plane calibration become important?
It depends on whether you really need accurate phase measurement at your device under test. If you only need SWR or return loss and don't care about the exact complex impedance or the phase of S11, then it doesn't matter.
Thank you for the video. It puts me one step closer to understanding how my NanoVNA works.
One question though. You demonstrated that even a short piece of coax can dramatically affect the measurements. However, you didn't connect your coax when you were calibrating the NanoVNA. Could this introduce an error in the measurements of your antenna?
Not an error, but just a different impedance due to the measurement location. When you have a non-resonant antenna as a load, the IMPEDANCE seen at the transmitter end of the coax WILL change with the coax length, but the VSWR will NOT change with coax length. So, if your goal is to measure the antenna SYSTEM (antenna+feedline) in order to adjust it for minimum SWR, then calibrating at the VNA and measuring at the tx end of the coax is perfectly OK (and correct). However, just remember that the IMPEDANCE seen at the tx end of the coax is not the impedance of the antenna itself. In order to measure the impedance of the antenna itself, the calibration plane has to be at the antenna - either through direct calibration with the standards applied at the antenna end of the coax, or possibly through port extension.
@@w2aew thank you for the reply. That's a lot to take in, and I have a lot of ground to cover. I will study this a little more.
Great video! Thx!
Just a question: Can we do the calibration with an 50-ohm extended cable? Or we should use electric delay function? which one is the proper way?
Ideally, you would attach the cal standards at the same place/location that your device-under-test would connect. If that is at the end of a cable, that's fine. The idea is to calibrate "out" the affects of the cable (attenuation, delay, phase).
@@w2aew Thank you!!
Great video once again. What NanoVNA model are you using? And who makes that neat e-ink pad you're using (high quality PDF exports 👍)
I think it's the ReMarkable ebook.
I'm using the nanoVNA-H4, and the e-ink tablet is from www.remarkable.com
$399 + Marker from $49
Would be good if you did a complete calibration including the thru and isolation.
I'll include that in a future video where I talk about measuring a device like a filter.
Thanks for the video, great help in calibrating my VNA V2. I have a question for you, when I connect my antenna directly to the VNA is get a nice circular smith chart, when I add the extension coax I get a smith chart that is made up of lots of overlapping star shaped patterns. What would be the cause of this? I have check the coax for continuity and shorts. Thanks
When you add coax, each point on the Smith chart gets rotated around the center by an amount that is proportional to the line length in wavelengths. Thus, the higher frequency points get rotated more than the low frequency points, which can space those points out further, making the curve more jagged or star-like.
@@w2aew Ah I see, so as long as the impedance stays near 50 ohms and the SWR near 1, I should be good to go. Thanks
@@simonhanlon7518 yep!
In most of your videos, you reset the calibration, calibrate, and then save it in one of the memories. Does reset affect the saved calibrations at all? And if you are recalling a saved calibration, would you do the reset first or just use the recall function?
Reset only affects the calibration that is in use at the time. It doesn't clear any saved calibrations. It's a good idea to clear the one in memory before either running a new cal, or recalling a saved calibration.
great video! what eNotebook are you using?
www.remarkable.com
if my antenna is fed with rg213 ,should i calibrate my vna after the adaptors etc and calibrate it by putting the open short load etc at the end of the coax where it joins the antenna,ie after all the adapters etc?
As long as the coax is not part of the antenna/counterpoise, then the SWR will not change with the coax lead length - in which case it doesn't matter which end you calibrate at. When measuring/adjusting an antenna, it is usually best to calibrate at the same location where the transmitter is going to be connected (NanoVNA takes the place of the transmitter).
Neat , thanks!