#95: Three Methods to Measure Impedance with the NanoVNA
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- Опубликовано: 1 авг 2024
- Are you aware that there is more than one method to measure impedance with a VNA? You might find this video interesting.
To download files from video:
www.dropbox.com/sh/iy89dyl4a1...
www.w0qe.com
So glad I found your channel and WebSite. Outstanding presentations of complex technology both on YT and your WebPage.
Oddly Three Methods to Measure Impedance with the NanoVNA didn't show any measurements!
Larry, Great video! This information is so vital for making accurate impedance measurements Thank You
Thanks Joe!
Thank you, that was a very clear summary with good technical details behind it.
Thanks Don!
Thanks, great explanation!
Larry, I find your videos a great source of knowledge. The challenge to understanding measurement techniques is extremely important. Thank you.
Thanks Danny. I find this stuff to be very interesting and enjoy sharing it.
Larry
@@w0qe Larry have you every thought about writing a textbook to support a Smith Chart class? I wish this type of information was available when I started my RF career.
Danny,
I thought about it a while back but that sort of seemed like a job and I really like my life without a job. Go trail running one day, mountain bike on another day, debug beta versions of SimSmith and do occasional videos when the weather is crappy or if my body is too tired. Also I think the world seems to have shifted from book learning to video learning. The advantage of a book would be to be able to use it as a reference.
I also wish a lot of this information was available when I was younger. It is interesting to be able to see how competent the old RF guys were without computers. My video #44 on the Johnson Matchbox ruclips.net/video/OvRI1m4bBjQ/видео.html showed how a matching network with only a fair matching range could work great provided you were trying to match an antenna similar to what it was designed to for.
Larry, W0QE
@@w0qe Larry, I completely agree with you on it being a job, I'm just learning how to use this new learning method. I'm getting ready to retire my electromagnetic effects career and pursue my other distractions. I appreciate your videos and insight fulness, thanks, Danny KI6VBC
Very good post, impedance measurement is my most common use of VNA.
AIM-4170 is excellent in shunt mode, and I often make fixtures for high impedance measurements.
If I measure anode plate choke, I may add known capacitor in series to make impedance much lower.
Well I have had to watch this several times, stopping here and there while I hit alt-tab and switch between browser and SimSmith along with making notes for myself, and I have finally taken quite a lot away from this video.
Admittedly, a lot of your content at this point in my understanding goes 'straight over my head', but I am getting numbers that make sense and from past bench experience that I would expect if I had the same circuit in-front of me in real life.
I cannot express my gratitude in words, but Larry, you are one hell of an Elmer and have helped me so, so much since I first heard of SimSmith and subscribed to your channel.
73 De 2E0IIZ
There is a lot to be learned when you can simulate a circuit and make it agree with what you build and measure. Glad you enjoyed the video.
Larry, W0QE
Could you please provide links for an education on using the NanoVNA-F v3.1 from a beginner? From my perspective, you need to use a White Board on one side and slides or images on the other side. Many of your expressions need to be written out and pointed out. You are very familiar with the text you are reading but the reader is not. Its just too complicated showing code without a diagram. Its a clear summary for those who already know the subject. I've been in antennas all my life and cannot follow you.
Pretty easy to follow, as usual great video.
Thanks Dragan
@@w0qe Do you speak Russia?I don't understand your video. Because you speak like English man. Where are you from?
I live in the United States.
Great video!!!
Thanks
As usual, GREAT video for people that know and understand SimSmith. Being an old dog that is unable to learn new tricks I personally would have learned more if you would have also done this with the NANO or other VNA. TNX 4 the upload ! 73 N8AUM
No one is too old to learn new tricks! The Nano isn't much different that many of the other inexpensive VNAs.
Larry, W0QE
Larry, first off thanks for doing this video. I'm still trying to get the hang of all this.
One thing that hangs me up about SimSmith, is (to me) the odd grouping of compartments LG1 & LG2; which have components grouped together that are actually from separate distinct circuits. Can you explain if the reason that the boxes encompass the components the way they do?
Thank You Very Much & 73...
W0QE can you show examples of measuring group delay and phase in various RF device using the NANOVNA because I'm don't understand what is the purpose of why would you want to know the group delay, time delay, phase of RF devices for what reasons?
Good info. My take-away is a 2-port VNA can measure a much larger range of loads than a 1-port.
Elwood,
Not sure if I would say a wider range but maybe be more accurate over a wide range vs a 1 port analyzer.
Larry
Larry, can you consider making a video, using the nanovna, on how to measure 1:1 coaxial chokes used to keep RF of of the outer shield of antenna feeds?
do you want to measure its common mode rejection or its self inductance ?
i guess i'll use a reference ground plane , two shorts termination at both sides to perform common mode injection and then load the shield/inner conductor to 50 ohm from the reference ground plane.
gen(50Ohms)(referenced to the ground plane) -->Sparam Test set S11 port (referenced to the ground plane) -->shortedcable(shield/innercond)--> Sparam Test set S22 port (referenced to the ground plane) --> receiver (50ohms referenced to the ground plane)
could be seen as triaxial test bench method
You can simply measure impedance between two ends of coax shield. High impedance is expected, so you can use series method. I use AIM-4170, it is fantastic in shunt mode.
I experimented a bit with ceramic and crystal filters to see if I could determine their input and output impedances using a NanoVNA H4. I used the series measurement but ran into some difficulties. Trying to determine the S21 value proved to be problematic as the value varied widely because of the passband ripple of the filters. I'm not sure whether I approached the problem correctly or not - maybe I got it all wrong! Can you perhaps elaborate on how exactly one should go about determining the S21 value using a NanoVNA ? A practical example of how to do this would be of great value.
Jacques,
From the words you used I am going to assume that you are measuring filters that someone else designed and did not design them yourself. My apologies if that is incorrect and please let me know. All crystal filters that I have ever measured had design impedances in the range from about 20 ohms to 300 ohms so I would just measure them in the standard shunt connection mode. To get them to measure correctly you will need to measure s11 and s21 with the output terminated correctly but this is the value you are trying to determine. Making the problem more difficult is that the filter bandwidth is very narrow and you need to sweep a small range with a large number of points.
I have done a couple of videos on crystal filters (videos #26 ruclips.net/video/LyAQqqIsBOM/видео.html and #27 ruclips.net/video/Y0_H8e4QTy8/видео.html ) which might help.
The filter will only have the proper s11, s21, s12, ans s22 when it is properly terminated. Would a video on this topic be helpful?
Larry, W0QE
@@w0qe Hi Larry, thanks for your prompt reply! Yes, I'm measuring commercial filters (Yaesu XF-92A and Murata CFM455D) purely as an exercise to learn. From what I could gather online the Yaesu filter has an impedance of 500Ω and the Murata is 1500Ω, which is why I tried the series S21 measurement. I'm very new to impedance matching but really want to get a good grip on anything related to the topic - I find it all quite fascinating. I will have a look at the videos you referred me to and experiment some more. I think a video on the topic will be of great interest to many people. Once again, thanks for your time! Jacques ZS1PL
@@w0qe yes, yes please! I was doing the same exercise as Jacques with an ECS monolithic crystal filter at 10.7MHz 7.5kHz wide. The datasheet shows 4pF//1.8k and it's easy enough to get an L match in auto mode in SimSmith and it works fine but I am trying to figure the proper method to mesure these values in the first place when you don't have the datasheet and a 50 ohms VNA. An LCR gives me the 4pF, but measuring one side on a 50 ohm reflection bridge while the other end is open gives me 25ohms at f0, way off but seems reasonable for a single crystal, i.e one side of the filter. getting lost here...
Thanks for that video. 73. PU2OOM
Thanks>
Larry, W0QE
tooo fast to comprehend
Clickbait! The video has no specific information about nanoVNA measurements, just a general explanation of the basic principles.
It is too bad you feel that way and hope you didn't waste your time with the video. Too many people feel as if the nanoVNA is less than a real VNA and that is not true and it may be accurate enough for most users. I make absolutely NO money from any of my videos so what would be the purpose of clickbait?
Larry, W0QE