Some of this goes right over my head. I have a Nano VNA-F and from your tutorials and a few others I am starting to understand how to use it. I even did a short presentation to my club and they didn't shoot me down so I reckon I got it about right. And we have some real electronic experts and I'm just a now retired mechanical engineer by training. Looking forward to the next one as I also have a pre amp stage to test out and I'm not entirely sure how to do it. Thank you Ralph.
Yeah, it takes time to sink in. Learning this stuff is not an overnight thing. Oh, and please note that I have a series of VNA introductory videos that goes over all the basics like terminology and the like. Here is a link to the first video in that series: th-cam.com/video/8IhJMGxU5xA/w-d-xo.html Maybe some of that will help? You are very welcome! I totally enjoy being a help to folks! 🙂
I like theory videos but the more interesting content is exploring why things don't match what you expected, that's where real science/engineering comes in. I appreciate the videos and explanations, I recently purchased a NanoVNA to get a more hands on understanding of various concepts like how ground plane size and material proximity affects performance of various antenna. I find reading books and articles is a good start but I need to be able to play with test equipment and components to build a more intuitive understanding, it's been a cool tool so far and your videos have motivated me to become more educated on these topics. Looking forward to the upcoming video on measuring a preamp.
I do a lot of the same stuff! Have you tried virtual antenna experiments with an antenna modeling program? I use 4NEC2 (because it is FREE). I usually do all the modelling and experimentation virtually before I implement it in real life. I have a number of videos on how to use the program. Here is a link to the first video in that series: th-cam.com/video/Zd6BT558YRA/w-d-xo.html 🙂
I don't think it's as bad as you made out. I generally like to look at the location of the passband to estimate the quality of the filter rather than the center peak. Since the -3dB values are pretty good, I think the filter is overall pretty good. Just remember, a small bit of parasitic capacitance could move the maximum point a good deal considering how flat the passband is. Looks like I'll have to get a nanoVNA, as it looks like an interesting tool. Cheers!
Thanks! On top of all of that, there is also a lot of stray inductance in there (like the jumper!). Totally an UGLY implementation clearly not intended as something I'm going to keep. I re-engineered the filter for a lower frequency range (for fun and sanity) and the final frequency response turned out real nice. I think you would have a blast with a nanoVNA! 🙂
Thanks for making all of these great videos? I wonder how you can check an I.F. transformer on an old (1940) radio with a VNA? No videos or anything available on this subject that I can find. Take care and 73!
Well ... first you would have to take it out of circuit. For a quick check, you could just connect things up. Be aware of the signal voltage level limitations that may or may not exist for it. You MAY need to attenuate the port signal to accommodate those limitations. For more precision, you need to determine what the input and output impedances *should* be so you can match impedances in the measurement. The proceed as shown here. Check out the video on the making measurements in a non-50 World (th-cam.com/video/dgDS4rjb-GU/w-d-xo.html). This should help on this. 🙂
Everything is shown in the video as it was done, while it was done. Because of the way VNAs work, when you do the "calibration" properly as I did in the video, all of the oddities that might have been introduced by the "pluggery" is "calibrated out." What I mean is that the VNA reads all of that stuff during calibration and then "backs it all out" during the measurement. This way, your measurement is ONLY of the unit you are testing. 🙂
Well you're in luck! The very next video that is coming out (in two weeks) is measuring the frequency response of an active device. I will be using a 20 dB receive preamplifier for the demonstration which operates in the 144-148 MHz range. 🙂
Hi Ralph, Is there anything special about the open and short standards, can one just modify a connector with a short and call it good. What about the open standard can the same type of connector used for the short standard be used, but without the short installed?
Really good question! The big difference between very expensive, lab quality shorts and opens and the kind that are "good enough" for our use is certain aspects of construction and calibration (measurements of delays and the like). For what we do, you can take a connector, remove its center pin and you have an open "standard." The short standard is a bit more of a challenge. I used braid (coax shield or pieces of solderwick) to make the most massive short between the center pin and the body of the connector that I could possibly make. For what the average guy does, this would work just fine. Hope this helps. 🙂
@@eie_for_you Ralph, Yes its does thanks for the explanation I do have the SMA standards for the VNA, but no N-type or PL type standards. Looking on Ebay and other places the price of lab quality standards can get pricey so making my own is my best option as of right now.
@@U812-k7j Yeah, lab quality standards are ridiculous. You could use your nanoVNA using a port extension to evaluate your resulting standards. Cal with the SMA standards, add adapters to bring you to where you can connect your homemade standards, do the port extension, then connect your standards and see how they look. As a note ... in the professional R.F. world, the SO-239 is referred to as a "UHF female" and the PL-259 is referred to as a "UHF male." Knowing this will help you find stuff on the more professional sites. 🙂
Well...depends on the quality you are looking for. The hard one is the load standard. A good quality N-type RF termination like this one (www.mouser.com/ProductDetail/Mini-Circuits/KARN-50%2b?qs=xZ%2FP%252Ba9zWqbbyDyxB2ryNg%3D%3D) is probably sufficient for a lot of what we do. My first short and open standards were just N connectors. The open was the connector without a center pin. The short was a connector with a MASSIVE short between the center pin and the body (I used some braid out of some coax). I made the semi-mistake of buying a kit through Amazon. The short-open was amazing (that is the two ended one). The load was TOTALLY BAD NEWS. I dropped back to my 50 termination and threw the one that came with the kit in the trash. There are a number of DIY calibration kit articles out on the internet as well. If you do decide to create your own load, DO use surface mount resistors. They carry a whole lot less RF baggage than their leaded cousins. If you want a real calibration kit that is professional quality, then you are talking MAJOR $$$. You can drop thousands of dollars on that one. Because I have a higher end VNA, I wanted a better calibration kit, but I didn't want to spend that kind of money on one. I found a *reasonably* affordable one here: www.kirkbymicrowave.co.uk/Sales-and-Services/Vector-network-analyzer-calibration-kits/N-calibration-kit/. $680 USD. Hope all of this helps. 🙂
True that! And this was just a throw together filter for demonstration purposes. The values were assumed based on their source (the marked container they were in). Oh well, if this were a real project to create a real filter for a real end use, then several things would have changed including the really crude implementation and the absolute determination of component values and their potential tolerances both in value and as they respond to temperature variation in the anticipated application environment. 🙂
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Some of this goes right over my head. I have a Nano VNA-F and from your tutorials and a few others I am starting to understand how to use it. I even did a short presentation to my club and they didn't shoot me down so I reckon I got it about right. And we have some real electronic experts and I'm just a now retired mechanical engineer by training. Looking forward to the next one as I also have a pre amp stage to test out and I'm not entirely sure how to do it. Thank you Ralph.
Yeah, it takes time to sink in. Learning this stuff is not an overnight thing. Oh, and please note that I have a series of VNA introductory videos that goes over all the basics like terminology and the like. Here is a link to the first video in that series: th-cam.com/video/8IhJMGxU5xA/w-d-xo.html
Maybe some of that will help?
You are very welcome! I totally enjoy being a help to folks! 🙂
You know it's going to be a good day when Ralph posts a new video. Thanks Ralph! Learning is FUN.
🤓Thanks! ... and you are welcome! Yes, learning IS fun! (and it keeps your brain healthy, too!) 🙂
I like theory videos but the more interesting content is exploring why things don't match what you expected, that's where real science/engineering comes in. I appreciate the videos and explanations, I recently purchased a NanoVNA to get a more hands on understanding of various concepts like how ground plane size and material proximity affects performance of various antenna. I find reading books and articles is a good start but I need to be able to play with test equipment and components to build a more intuitive understanding, it's been a cool tool so far and your videos have motivated me to become more educated on these topics.
Looking forward to the upcoming video on measuring a preamp.
I do a lot of the same stuff! Have you tried virtual antenna experiments with an antenna modeling program? I use 4NEC2 (because it is FREE). I usually do all the modelling and experimentation virtually before I implement it in real life.
I have a number of videos on how to use the program. Here is a link to the first video in that series: th-cam.com/video/Zd6BT558YRA/w-d-xo.html 🙂
Fantastic video! 😊 73s
Thanks, man! 🙂
Thank you! This is the best video I’ve seen on this topic.
Thanks so much! 🙂
I don't think it's as bad as you made out. I generally like to look at the location of the passband to estimate the quality of the filter rather than the center peak. Since the -3dB values are pretty good, I think the filter is overall pretty good. Just remember, a small bit of parasitic capacitance could move the maximum point a good deal considering how flat the passband is. Looks like I'll have to get a nanoVNA, as it looks like an interesting tool. Cheers!
Thanks! On top of all of that, there is also a lot of stray inductance in there (like the jumper!). Totally an UGLY implementation clearly not intended as something I'm going to keep. I re-engineered the filter for a lower frequency range (for fun and sanity) and the final frequency response turned out real nice.
I think you would have a blast with a nanoVNA! 🙂
👍Thank you sir.
You are welcome! 🙂
Great, thank you for your video. I'm starting to measure what I'm building:) At the mememnts balluns only. But this is ultra helpfull. Thx again.
Thank you! ... and you are very welcome! 🙂
Ralph 👋😎
Thanks! :-)
Thanks for making all of these great videos? I wonder how you can check an I.F. transformer on an old (1940) radio with a VNA? No videos or anything available on this subject that I can find. Take care and 73!
Well ... first you would have to take it out of circuit. For a quick check, you could just connect things up. Be aware of the signal voltage level limitations that may or may not exist for it. You MAY need to attenuate the port signal to accommodate those limitations.
For more precision, you need to determine what the input and output impedances *should* be so you can match impedances in the measurement. The proceed as shown here. Check out the video on the making measurements in a non-50 World (th-cam.com/video/dgDS4rjb-GU/w-d-xo.html). This should help on this. 🙂
@@eie_for_you Thanks!
@@W1RMD You are very welcome! 🙂
id like to see the sum of all your pluggery and how it messes with the results
Everything is shown in the video as it was done, while it was done.
Because of the way VNAs work, when you do the "calibration" properly as I did in the video, all of the oddities that might have been introduced by the "pluggery" is "calibrated out." What I mean is that the VNA reads all of that stuff during calibration and then "backs it all out" during the measurement. This way, your measurement is ONLY of the unit you are testing. 🙂
please make videos about how to measure active filter used in frontends(88-108 mhz). or if you have any suggestion...
Well you're in luck! The very next video that is coming out (in two weeks) is measuring the frequency response of an active device. I will be using a 20 dB receive preamplifier for the demonstration which operates in the 144-148 MHz range. 🙂
Hi Ralph,
Is there anything special about the open and short standards, can one just modify a connector with a short and call it good. What about the open standard can the same type of connector used for the short standard be used, but without the short installed?
Really good question! The big difference between very expensive, lab quality shorts and opens and the kind that are "good enough" for our use is certain aspects of construction and calibration (measurements of delays and the like). For what we do, you can take a connector, remove its center pin and you have an open "standard." The short standard is a bit more of a challenge. I used braid (coax shield or pieces of solderwick) to make the most massive short between the center pin and the body of the connector that I could possibly make.
For what the average guy does, this would work just fine.
Hope this helps. 🙂
@@eie_for_you Ralph,
Yes its does thanks for the explanation I do have the SMA standards for the VNA, but no N-type or PL type standards. Looking on Ebay and other places the price of lab quality standards can get pricey so making my own is my best option as of right now.
@@U812-k7j Yeah, lab quality standards are ridiculous. You could use your nanoVNA using a port extension to evaluate your resulting standards. Cal with the SMA standards, add adapters to bring you to where you can connect your homemade standards, do the port extension, then connect your standards and see how they look.
As a note ... in the professional R.F. world, the SO-239 is referred to as a "UHF female" and the PL-259 is referred to as a "UHF male." Knowing this will help you find stuff on the more professional sites. 🙂
Hello, where did you get N-type open/short/load standard connectors? Any helpfull link/name? Thank you, 73
Well...depends on the quality you are looking for. The hard one is the load standard. A good quality N-type RF termination like this one (www.mouser.com/ProductDetail/Mini-Circuits/KARN-50%2b?qs=xZ%2FP%252Ba9zWqbbyDyxB2ryNg%3D%3D) is probably sufficient for a lot of what we do. My first short and open standards were just N connectors. The open was the connector without a center pin. The short was a connector with a MASSIVE short between the center pin and the body (I used some braid out of some coax). I made the semi-mistake of buying a kit through Amazon. The short-open was amazing (that is the two ended one). The load was TOTALLY BAD NEWS. I dropped back to my 50 termination and threw the one that came with the kit in the trash.
There are a number of DIY calibration kit articles out on the internet as well. If you do decide to create your own load, DO use surface mount resistors. They carry a whole lot less RF baggage than their leaded cousins.
If you want a real calibration kit that is professional quality, then you are talking MAJOR $$$. You can drop thousands of dollars on that one. Because I have a higher end VNA, I wanted a better calibration kit, but I didn't want to spend that kind of money on one. I found a *reasonably* affordable one here: www.kirkbymicrowave.co.uk/Sales-and-Services/Vector-network-analyzer-calibration-kits/N-calibration-kit/. $680 USD. Hope all of this helps. 🙂
@@eie_for_you Wow, Thank you very much for you help:) This will help me a lot. 73
@@zygmunt73 I am very glad for that! 🙂
Haha. Already adjusting theoretical prediction by changing values used in calculations. Knowing component values accurately is step zero.
True that! And this was just a throw together filter for demonstration purposes. The values were assumed based on their source (the marked container they were in). Oh well, if this were a real project to create a real filter for a real end use, then several things would have changed including the really crude implementation and the absolute determination of component values and their potential tolerances both in value and as they respond to temperature variation in the anticipated application environment. 🙂
@@eie_for_you I'm sure you could do all that. Just need to get an lcr meter and do things in order.
@@jspencerg I prefer to use my Tektronix VNA when values matter. In this case ... not so much.