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- Опубликовано: 2 июн 2024
- The user calibration, described in video #313 ( • #313: Why a VNA needs ... ), establishes a calibration or reference plane for the complex reflection/impedance measurement on the VNA. If you need to use adapters, fixtures, cables, etc. to connect to you DUT, you may need to apply a port extension to move the calibration plane to the DUT end of these "additions". This video discusses what a port extension is, why you might need it, and how to do it on the NanoVNA.
Notes from this video: www.qsl.net/w2aew/youtube/Nano...
0:00 - Start
0:15 - Review of User Calibration and Measurement Plane
0:56 - What if your DUT Connection and Calibration Plane don't match
1:40 - Port Extension introduction
2:43 - How-to do Port Extension on the NanoVNA
3:09 - Live demonstration begins - intro
4:09 - Effect of adding an adapter
5:36 - Add Electrical Delay to extend the port (port extension)
7:20 - Summary 
Наука
Really neat tool! Thanks for making such a great video series on these. I like being able to follow along at home using mine. 73 and take care.
Thank you as always! I think it's worth to mention a simple calculation of the delay value = (phase / 360) / frequency, it gives 167ps to correct 53 degree phase shift at 882MHz in your example.
To be precise one should take into account the velocity factor which is not equal to 1 in case of a non-air-filled coaxial line like in this example. That means that wavelength is shorter and the phase shift is greater than expected.
it been a while... need a refresher course on this... itt we went over smith charts
Your content is excellent, well organized, thoroughly explained, well demonstrated and well paced. On top of all of that your voice and delivery are both engaging and relaxing.
Thanks for teaching me and helping me relax.
Thanks for making this video Alan, it gave me the information I needed for testing antennas which needed adaptors to hook up with the VNA.
this is very useful. I will come back again looking for another tutorial
I learned the name electrical delay before port extension because the PNA at work calls it electrical delay. I didn’t know that electrical delay wasn’t the industry standard name of adding linear phase. That’s aside, great video as usual. I watch these before I go to bed. Great way to relax and learn/review things that I am interested in.
Newer firmware you can set the scale of one of the traces to "Delay" and it will give you an accurate electrical delay to input 👍🏼
Excellent explanation of a process to make this unit as accurate as possible. Thank you for sharing.
Great description and easy to understand for dumb folks like myself! Thanks!
Thankyou. This has driven me nuts doing cable cals as it always bothered me that i cant cal out the last adapter. Now I know what the solution is "Port Extension". And you mention that as my work is close to DC I need not worry.
Alan, your timing is perfect. I was just looking for a way to accomplish port extensions. Great
explanation. I look forward to all of your video's. Please keep the nanovna videos coming.
Hi W2AEW! Very interesting video. Good thing you made clear that this measurement plane shifting method only holds for situations when no real impedance transformations or non linear phase changes occur. I work in the RF industry and have found the .spar data from semiconductor manufacturers to also have used port extension for measuring a device on a microstrip eval board. In the resulting data very clearly can be noticed that a lot of irregularities are not deeembedded perfectly since the reflection curves are curling anti clockwise in the Smith chart. Incorrect device behaviour due to port extension, never seen it when correct TRL or TOSM calibration has been utilized. I.e. Coaxial SMA to microstrip transition on a RO4003 PCB are absolutely not suited for port extension, even at S band already. Definitely need an PCB cal kit.
You are definitely right. I always add calibration standards to test fixture PCB hosting the DUT. TRL calibration using these embedded standards placed at the desired reference plane performs quite well, provided that frequency range satisfies phase variation between 20 and 160 degrees for phase unambiguity as per TRL requirements.
@@paolomonai9511 Regarding the frequency ranges: utilize multiple TRL lines with center frequencies according to predetermined frequency ratio. Most of the time ratio 4. I.e. Line 1: 0.25to1GHZz, line 2: 1to4GHz, line 2: 4to16Ghz.
@@stefanhummelink3662 Yes, of course the use of muliple lines is the right thing to do for a very wideband characterization, for example multioctave bandwidths. Regards from Italy.
And the moral of that is: ALWAYS get a sample first and measure it yourself!
@@hectorpascal If you want to be sure that a job is well done, do it by yourself...it is the only way!!! Regards from Italy.
Thanks for making a video that explains in more detail your answer to my question in my calibration video's comments. I appreciate this; I may try using this with the nanoVNA V2 when working at L band and above. That or I might finally go buy a female cal kit :)
Very helpful demo, I am still waiting for my nano vna to arrive...
Thanks for video. I want measure impedance of pcb antenna and this information very important for me. Now i know, how to shift measure plane.
This video got me pumped on using the port extensions for a measurement I made, thanks for the help!
Looking forward for more videos about using NanoVNA.
Please do a video about measuring and tuning baluns on the VNA.
and please add coaxial chokes to that, too. although they are pretty close to each other
And if you could, please include how to measure CMRR in a Balun. I have been looking into this and found some info but there seems to be multiple methods and nothing I found explains it in a away I fully understand. Thanks for all your great videos. I have learned a lot from them.
Thank you so much you were very helpful, learned a lot. I also realized that in setting up calibration with the RF demo board , I was leaving out 1 step (watching other video's that said it didn't need to be done when in fact it does) Open-short-load-and thru cal. I wasn't doing the thru. Thanks again, this video was very helpful also.
Thanks for the lesson, I like the idea of using complex impedances which is something I missed out of.
Hi Allen,
This explanation worth two thumbs up. :-) Stay safe. 73 WJ3U ex WB3BJU
Thumbs Up, thank you for teaching us!
Very very informative video... You are a great teacher. It would be just awesome if you please make video on different types of AGC for an RF receiver and how they work.
Your Best ❤
You can perform some simple deembedding using the software on the pc… this will allow you to account for the impedance of any adapters and the coax line itself.
Very helpful, thanks!
Thank you for this wonderful video. Would you please sir make a tutorial(or a series) about digital electronics or maybe explaining the serial data protocols? Your the best teacher of this field. Thank you for your work and hope you stay healthy sir.
That was another great and educational video. Thanks so much Alan. Would you consider doing a video on phase stable test cables? I'm way out of my league here but my OCD demanded that I get them and I'd like to know more about their importance. Thanks again for all of your efforts. You have taught us so much. Greetings from Arizona K8MB.
Well, I can't afford phase stable cables either, so I don't have any to demonstrate/show.
Great series! Thx
In some commercial VNAs this correction can be automatically done under "autolength" menu.
As always, great video Alan.
You made it so Even I can understand this. Thanks
Thanks for the video series regarding and info as always! Just noticed today on the groups.io some newer versions are on the way... and looking like cost effective to be used up to 6GHz. Now, if there was only a mod/hack that lowers the noise floor on the HackRF to improve that devices performance since is open source also and with two I'm thinking can be used the same. The oscillator upgrade is well documented for starters and designed to have.
Thank you! This is just great.
Thank you for another great video! I would also be interested in seeing a video working with baluns.
Check Gregg Messenger's channel
@@RobertResearchRadios Thank you. I also find Gregg's channel informative. But although I am quite new to this I feel that more could be done than measuring common mode rejection. For instance can I use the nanoVNA to measure the characteristics of an unknown balun without tearing it apart?
Thanks you for idear it very helpful for me.
Appreciate these nanovna operating videos, really helps puzzling out the menus. Would also like to see how accurate it is compared to your lab equipment. 73
What a great video, making the Smith chart easy to understand. Thanks! 73 de KT1R Lou
I've got several other videos that describe a lot more about the Smith chart.
great video
No question, there is your thumbs up.
Thanks again for another wonderful video! Can you tell me what kind of new stainless steel connectors you added to your VNA to protect the ports? And was calibration done before and after you added them? Also, would you consider a video on calibration kits? I have noticed that many cheap kits have opens, loads, and shorts that are not always 50 ohms.
They’re a pair of m-f adapters (connector savers) from Mini-Circuits. Calibration was done after adding them.
@@w2aew Thank you sir!
@@w2aew I forgot to mention why I requested a calibration kit video. I'm expecting the NanoVNA-F soon and there is a beta firmware to increase the frequency to 2.7gigs. Cheaper kits may be okay up to 900 M but calibration may be off at 2.7. Thanks!
For those interested: www.minicircuits.com/pdfs/SF-MQK50+.pdf
Given that many people including me loving your way of explanation...I request you to explain Maxwell equations in your style if possible. That would be great help :)
How does adding this delay differ from just doing a new calibration to include the extra connector? I thought the cal took the extra length into account.
Performing the calibration at the far end of the added connector, fixture, etc. is the PREFERRED thing to do, this will take the extra length into account. You would use Port Extension *only* when it isn't possible to do this (maybe due to mis-matched connector types, etc.).
@@w2aew If I am using a small coax cable from my VNA that does not have a standard SMA connector on the DUT end but rather a stripped piece of wire that I solder to my board, can I just use a 0 OHM, 50 OHM and no resistor to perform the calibration ?
@@eduardorey8238 often times yes, but gets trickier as you go higher in frequency.
@@w2aew I also need to solder a coax to the PCB to tune the Pi network of a Bluetooth LE ceramic antenna. Is there a way to verify that the 50 Ohm resistor behaves like a resistor (inductive/capacitive part stays negligible) and that the calibration is somewhat valid?
@@marcspeck If you complete the calibration to the ports of the VNA, then solder the same type of 50 ohm resistor to the end of the coax, and connect that to the VNA, it should still look like a 50 ohm resistor (because a properly terminated 50 ohm line will look like a 50 ohm resistor). Then you'll know that the far-end termination is OK. Otherwise, you can use Port Extension.
NanoVNA is also a signal generator, powerfull enough to radiate at several meters of distance if connected to an antenna. It can be used to test antennas in the near field and receivers.
Thank you for that explanation. Is it fair to say that you can do open short load at the end of the coupler right?
Thanks for making a video that explains the process in detail. Can you please make a "Basics" video explaining Op Amp as precision signal rectifier and logarithmic amplifier?
They're on my "long list" of future video topics.
@@w2aew Thanks, till then we wait and enjoy your excellent video !
Great informative videos. Is there a way that that I could measure the impedance of a choke/line isolator/ferrites on the feed line to my antennas just to see if i have the correct impedance value for the frequency ?
The answer is a qualified yes - meaning that there are a few ways to measure impedance, and each method has different limits of impedance it can measure accurately. Some involve some calculations. I hope to do some videos on it - it is a very popular question.
Excellent demonstration! I'm just waiting for a 4" screen nanovna version to be announced. Having poorer eyesight than the younger guys who design these great, but tiny, instruments really sucks! :(
Yes! Maybe one with a HDMI output ?
I have had instructors in the past that, for me for example, made everything so easy to understand but for others flew right over their head. Your style makes it easy for even the slow Learners to understand but not boring for someone, for example, like me. Thank you so much for doing this for us!
If you need a larger display, you can connect it to a computer and use a program like NanoVNASaver.
Me too
The one that I am using is a 4" screen. It is the NanoVNA-H4. Another 4" version is the NanoVNA-F.
Thanks!
Love your videos. I have learnt more from them than any of time I spent in school traggling numbers.
I have one question though. I need to match an antenna to a PA with an output impedance other than 50ohm and my VNA only has 50 ohms output. What should I think about when doing this?
Maximum power transfer from the amp to the antenna system (antenna plus feedline) will occur when the input impedance to the antenna system is equal to the complex conjugate of the amp's output impedance.
Thanks Alan for the video. I sure wouldn't figure this out from the 1 page "manual" that came with my unit. I ended up buying the NanoVNA-F version not knowing there were other versions. I ordered it "without battery" as paying almost $50 extra for a battery seemed exorbitant considering what batteries cost in China. Surely it would still have some small battery that would maybe give 1 hour of use? After all it is a portable instrument. But NO, it seems to have no internal battery so I have to power it from a power bank. Why would you make a portable instrument without a battery?? I had hopes at first that it did have a battery as I get the flashing red light when connected to power and the blink rate goes down but no luck. Will go back and re-watch your other videos. Thanks again.
There are safety concerns regarding the shipment of Lithium-based batteries - some people would rather not take the chance. And some hobbyists already have these on hand, and can save money by receiving a cheaper unit without one.
Can you talk about or show a lot of different examples of when to use the electrical delay setting in RF circuits? Why would you want to use the electrical delay to measure an RF filter, RF amplifier, etc?
Hello Alan! I didn't realize such a calibration factor existed. Thank you so much!
Where did you get the housing for the Nano? Noting comes on AliExpr
I believe that all of the NanoVNA-H4 models come with a housing.
Thank you sir for another very well done educational video. Since a scalar network does not measure phase, are extensions less of a problem? I assume that when using a scalar network to measure something such as VSWR / return loss, the VSWR / retrun loss of the RF adapters / extensions will be the parameter that largely effect the instruments measurement?
Even though they don’t measure phase, the amplitude of the signals on a line with reflections is still affected by phase.
@@w2aew Thank you!
Fantastic video. Yesterday I watched a Keysight webinar on a similar topic. Can you make follow up video on that 4 port copper board on your tabel on say some simple DUT? Also where can I buy those sma connector savers? What is the technical name for them?
0 dB attenuator pad? I took a look on digikey and a 1 dB pad is like 142 $ ? Can you post the link to buy these savers?
Great video!!!
The connector savers are also simply known as a male-female adapter. Here is a good example:
www.minicircuits.com/WebStore/dashboard.html?model=SF-SM50%2B
Thanks for your response, still lots of line on smith chart with it hooked to RF demo board. I understand the calibration but don't understand why the extra lines in the cap and inductance area of the smith chart ,when using this demo board. Using nano VNA F-v2, is there a setting I'm missing during the process, to calibrate at the end of the supplied cable.
I don't have an "F" model, but I assume that the calibration process is the same. Setup your stimulus frequency range, clear the existing calibration, run through the cal process applying the open/short/load at the end of the lead, APPLY the calibration and save it.
If you have an antenna at the end of your coax and want to find the vswr and resistance on your nanovna do you have to add in delay, or can you just open short load calibrate on the nanovna itself ?
If the antenna is balanced or has a proper counterpoise, then the coax will not change the SWR. The coax *will* transform the impedance, but not change the SWR. So if your goal is to learn/measure the SWR at your transmitter, then simply calibrate the VNA locally and make the measurement. If you wish to learn the actual feedpoint impedance of the antenna itself, then either calibrate at the end of the coax (then connect it to the antenna), or use the electrical delay setting to move the reference plane to the antenna (assuming you know the exact electrical length of the coax).
Hello, thanks for your videos, very instructive.
I have a PCB antenna to test with the NanoVNA and I cut the SMA cable to solder it to the PCB. I am having trouble correcting my delay because the phase is well over -104° at my high frequency which is 3Ghz and I have 165degre at the lower frequency 2GHz. My antenna resonant frequency must be around 2.45GHz.
Also, the curve in the Smith chart almost surrounds the first circle. What can I do to correct this?
Thanks
I've been watching a few of your videos and I have to say they are very informative. I was wondering if you would be able to show how the NanoVNA could be used to tune a 440 bandpass duplexer. I've only seen one video on it and that was in a foreign language and while I commend the users attempt, I feel the translations made it difficult to completely understand what was being done. You also seem to point out problems and pitfalls when it comes to the limitations of the NanoVNA and I feel that is helpful as well. Thanks
I think that you'll find that the NanoVNA lacks the required dynamic range to properly tune a repeater duplexer. This video shows this: ruclips.net/video/GipCVEsiqXc/видео.html
@@w2aew Yeah, it was kinda funny right after I asked the question I clicked on your video and found you had beat me to it haha, Thank you for getting back to me though :) 73's
you bet I did learn something new ! But tell me, why not recalibrate at the end of the extention or pigtail and then test at the end of that extention or pigtail ? I did test with a coax cable that ends with aligator clips with small wires and readings are everywhere ! I wanted to use those type of cable to test windings of a balun but I don't think it will be usefull unless I could correct those cable/aligator clips with electrical delay ? I've calibrated those test leads with OSL and still have crazy readings... Thank you for all these great tips on nanovna !
Unfortunately, flying leads with alligator clips just don't work well with a VNA because there is no controlled impedance - it varies as you move the leads around. The only way to get somewhat consistent results is to affix the leads to a stable physical location and then calibrate. Even with this, it will be difficult to get consistent results.
@@w2aew Maybe I should have get the BNC/Banana binding post instead, they are "fixed"... Thank you for the precisions and awesome videos !
Maybe you're happy with a guitar pick, but found a nintendo DS Lite stylus works perfectly on the NanoVNA, and you can get them absolutely dirt cheap.
Hi Alan, I was just about to email you and ask about this very topic of port extension as many UHF RFID fixed reader antennas connectors are RP-TNC so I cal with SMA and then do port extension to compensate for the SMA to RP-TNC adapter to get S11 of the antenna. Thanks so much!
-Lou
Awesome, glad this video was helpful! Nice to hear from you, old friend!
Thank you so much, i was thinking i would need more cal set for pl249. do think this would work over a longer say 5m length of 50ohm rg58 ?
Port extension assumes a nice, lossless extension of the 50 ohm environment. Depending on your frequency of operation, 5m of RG58 may introduce a few dB of loss, thus giving some misleading results when using port extension. Better off building your own OSL cal kit to use at the end of the cable if your goal is to establish your measurement plane there.
Could you do an item on cavity .. i have a 2c39 on 1200 Mhz that uses a cavity and i haven't got a clue on how that works. RUclips does not yet have an item on this topic
Off topic, but regarding converting a vintage scope into a curve tracer using the octopus circuit, can you use an early '70s portable black & white TV instead of a scope? Thanks!
Not really very practical - mainly because XY operation isn't very straighforward. It can be done though...
@@w2aew Alan, here is something interesting I've just now noticed after watching your videos for years; at 57, this new hobby reminds me of my 8~10 year old days. Had to hurry and take it apart and look inside. I.E Nice fly reel, 4 screwes later... Boing! Cahboom!... So I asked about a curve tracer crap portable tv. If it was easy, everyone... But, if some crazy person made a small b&w tv curve tracer, would it only be black and white? No cool green colors?
I've been using port delays with my higher end VNA and with my mini VNA tiny for a LONG time. I just didn't know how to get to them with my newly acquired nano VNA. The VNA View software hides it here View->Port Length Extension. The "Saver" app sports a "Delay" parameter in the calibration, but it doesn't appear to do anything. Thanks for pointing me in the right direction. (btw, do you play the guitar?)
Nope - I don't play guitar - I have no musical abilities whatsoever.
Which model nanoVNA is that in your video and do you have a link to buy it?
This is the NanoVNA-H4. In the US, here is a good source:
www.randl.com/shop/catalog/product_info.php?products_id=75145&osCsid=h25v4pc5ilnipaj13ddg8bs1p0
Hi, Alan, I have a Nano VNA and I have noticed the features are different to what I have on mine and I am wondering what version of firmware you have and have you recently updated it. I am curious as to what version of firmware it has?. Can you at some stage give an explanation of what they mean between the gain of S11 and S21 as return losses? I have used it on a homebrew antenna change switch and I am trying to work out how much of my injected signal is lost the SWR for the switch is reasonable up to about 70cm.
Many thanks.
Mine is the NanoVNA-H4 running the firmware it came delivered with (v0.5).
S11 is a reflection measurement - which tells you how much of the applied signal is being reflected back towards the source, and the phase shift induced by the reflection off of the DUT input impedance. It is also known as the reflection coefficient. 0dB means 100% reflection, and negative dB values indicate a smaller reflection. A perfect match would be a very large negative number. Return Loss is just changing the "sign" of the Reflection coefficient. Thus if the magnitude of S11 is -10dB, then the Return Loss is +10dB. The greater the number, the more return signal that is "lost" at the DUT input (i.e. more signal accepted by the DUT).
S21 is the transmission coefficient - i.e. how much of the applied signal passes through the DUT. If the DUT is an amplifier or active mixer, etc., the the signal coming out of the DUT can be greater than the applied signal. In this condition, S21 would be a positive number and would represent gain. When there is attenuation through the DUT, some of the applied signal is lost, and the S21 will be a negative number.
Hey Alen, if you had a nice Johnson Messenger 4230, and you lived in SLC UT with a window facing west, and you had NO antenna... I'm thinking two 10' sections of 3/4" pvc (easy & quick to assemble/disassemble, and cheep). But I have no idea of optimal cable run details. Any brief thoughts? I've been staring at my Johnson for two years now, and I'm still not sure how to handle it. Cheers! Dan ;)
There really isn't an optimal cable length - SWR does not change with cable length.
I didn't see any indication that delay had been added, are the settings persistant or are they set back to zero when you turn the device off?
They are reset to zero when to turn the device off. When the electrical delay has been added, it is shown in white text in the upper left of the display (Edelay value)
@@w2aew Thank you so much, once I got off my lazy butt and did it myself it became apparent, you are a muse, god bless.
I want to measure antenna performance, at the Balun, while it is in the air. So, could I do calibration (Short, Open, 50 ohm process) at the Balun's disconnected coax connection point, with the NanoVNA located at the far end, in the Shack (at the Transceiver connection point)? Thus eliminating the transmission line & lightning protectors from the readings, as I trim the antenna. Then reconnect everything and measure again at the transceiver end, to see the impact of the coax feed system.
Yes, if you can perform the SOL calibration at the balun end of the cable, this will take out the effects of everything up to that point, and will be superior than using port extension. Just be sure to perform that calibration over the same frequency range as your intended test.
@@w2aew Awesomely presented & timely videos on the whole VNA topic, which I am just starting to explore. I hope to apply the insights gained to my HAM Antenna DIY projects. Thank you so much for posting these videos.
I have been using the MFJ-269 as my 'goto' tester; and expect to receiver a nanoVNA -F shortly. After going thru the long list to nanoVNA variations found on Amazon, I picked the '-F' version; mainly for the larger display and the ability to store field values.
Do you have any comparative comments on the '-F' version of the nanoVNA, vs the one you use in this video ??
@@cache4pat I've never used the -F, so my comments are based only what I've read. The metal case on the -F is nice. Also, I like the fact that the -F *properly* labels the ports as Port 1 and Port 2, instead of CH0 and CH1 like the -H/H4. The -F also has vertical axis labels which are nice. But, I think the -F doesn't go all the way to 1.5GHz like the -H4. I think the RF performance of the -F is little better.
👍👍👍
Could you do the same thing by running the calibration with the extender installed
Yes you can. This tip is useful for situations where it might not be possible or practical to run the calibration with the extension included.
@@w2aew .I just ran through this with my Nano V4, Really easy.. And I understand why this would be helpful without disturbing your calibration settings. THANKS AGAIN ALAN !! *73* N8QZH
What is different between using the electrical delay feature and calibration after adding port extension?
One assumes a perfect 50 ohm extension and one doesn’t.
@@w2aew Thank you.
Why would I use this method, rather than a standard OSL calibration which included all the hardware upto the measurement plane? That is to say calibrate at the point of DUT connection.
Sometimes it isn't possible to use the OSL standard at the measurement plane of interest. One example is testing the impedance of a printed circuit antenna that is sitting at the end of a microstrip transmission line on the circuit board. The VNA would connect to the input of the transmission line, but the desired measurement plane is at the antenna end of the line, where the matching network would be applied. Port Extension would be used to "move" the measurement/reference plane from the input of the line, down to the far end (antenna end) of the line.
how are you getting no multiple circles on the smith chart with a lead hooked to S11. I've recently purchased an RF demo board and with the leads provided I cannot get rid of the multiple rings on the chart, even thou many videos don't show what I see, with the exception of 1 video and the guy just gave up at the end and said, not what he expected to see.
Are you calibrating to the end of the coax leads (putting the open, short, load at the end of the leads when calibrating)? That should remove the phase shift and resulting rotation on the Smith chart with nothing connected.
Complex impedence is very complex.
I wish someone would program the firmware so you you could use the jog wheel to adjust the electrical delay the same way the HP analyzers work like the 8714E series and the venerable 8753's.No guessing reqiured just wheel away!
Would love to buy a nano vna
How can we measure the NFC tag signal stregth using nanoVNA?
You really can't - it does not measure power directly.
Has anyone looked at the tracking generator output on port 1/CH0 using a scope? I was surprised to see that for some frequencies the output was sometimes a square wave instead of a sine.
It's actually *always* a square wave. It only tunes natively to 300MHz. Operation from 300-900MHz uses the 3rd harmonic of the squarewave, and operation from 900-1500MHz uses the 5th harmonic of the squarewave.
@@w2aew ahhh got it, thanks! Actually, I'm having a hard time calibrating it in the 900-1500 MHz band. The reponse here is not flat afterwards. Have you experienced this also?
@@mstjerning8919 I seem to get a decent result in 900-1500MHz. Not perfect, but not bad. It isn't going to be as good as the sub-300 and 300-900MHz bands for several reasons, the primary of which is because the stimulus signal is so much lower. It is 15-20dB lower than the fundamental (180 to 300MHz)
🌷
why can't you just do the calibration with the port extensions already attached ?
In the case I showed in the video, you could. However, in real life, it may not be practical to apply the calibration standards at that point (it might be buried in a circuit board trace or inside of an assembly).
The Electrical delay and Group delay are measured in RF filter circuits and RF amplifiers circuits to measure how long it take the RF signal to get from input to output which is the electrical delay and measure the passband frequencies which is the group delay because of why? the reason why to know the electrical delay and group delay of the RF filer and RF amplifier is because it will "distort" the receivers AM/FM/PM modulator circuit? and the RF receivers sensitivity input front end circuit?
You can think of Group Delay as a plot of electrical delay vs. frequency. Often times, the delay through a circuit will vary with frequency, and this can cause distortion in wideband RF signals.
@@w2aew how can electrical delay and group delay cause distortion in the RF signal? When using S21 gain or S21 phase I don't see the distortion in the RF, how can you tell an view the distortion on a VNA or Spectrum Analyzer? The Distortion will look like what
Unsubscribed from the channel because Google no longer sends email alerts for new content on this channel.
I will not go and be logged in 24/7 to get notified, they had to just make it opt-in.
I'm very sorry to see you go - I have no control over this. Are you saying that if you click on the "bell" icon that you are no longer seeing notifications?
Is it possible to just cailbrate the VNA after the adapters or cables are installed? I've been doing that to "move" the measurement plane to the end of a coax, but I fear that may have been a bad idea
Good question, as I have been doing the same thing and it seems to be working just fine. To me, I thought calibration took everything into consideration to include internal PCB delays and all to include cable length to the terminating end?
Hell yea! W2AEW shows the method in the video to work great of you do not have the option to calibrate at the end of your system connections! For lower frequencies this method by W2AEW works perfect, but if we as RF designers need absolutely accurate data you shall and cannot mitigate the correct and full 2-port TOSM or TRL calibration to calibrate your VNA system to either the end of your SMA(or i.e. smp) cable if your only interestes in the behaviour of your DUT with its connectors in total as a black box, OR to calibrate the VNA system to a plane right next to you DUT in a PCB for instance. For the latter your require a PCB callkit that contains the same connector transition to the actual PCB and should have a open and short standard at the plane location of interest. The callkit should also contain an through, which are simply two open standards connected back2back (no exactly true since the open standard it self should compensate for the fringing field at the open end).... The KIT also contains a match/load (perfect 50 ohm termination).
@H Higgins yea, sounds familiar. Luckily I get to use SMA/B/P interfaces for all my RF applications 😎.
For sure. Just connect the cables and perform calibration
Performing the calibration at the far end of the added connector, fixture, etc. is the PREFERRED thing to do, this will take the extra length into account. You would use Port Extension only when it isn't possible to do this (maybe due to mis-matched connector types, etc.). You have been doing it right!