I enjoy watching you videos. You made complicated things easy to understand and remember. Unlike many who produce videos showing their faces talking 90% of the time with 10% of which conveying useful information, you make very good use of time in a pace I can follow and enjoy for as long as it takes. I just bought a NanoVNA H4. With your wonderful instructions I was able to explore the use of Smith Chart hands on, in so many ways than I could ever imagined. "When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind.” ... Lord Kelvin You understand your subjects well and you can connect the viewers to your knowledge in an unpretentious way. Thank you and please keep up the good work.
Keep up the amazing work. You have made RF accessible to me, even though I never studied electronics. You calm, clear and methodical teaching style is pure gold.
I've only seen one other ham make instructional videos so well-made and easy to comprehend for us less-advanced hams, but sadly she went off in another direction. Thank you Alan for all the videos I've watched. I subbed after the first one I saw some years ago. 73 de w1ade
Alan, I served in the Marines for 9 years and 6 months . (honorable) You are the best teacher I've had the pleasure of serving this great country for. I took biology 101ish from the University of Maryland. "Intertidal organisms of Okinawa". I have seen the best of the best. I just would like to thank you for providing a far superior electronics education than most, if not all, top notch institutions. Realizing that you can manage to give it the elbow and give your videos away... To be honest, it brought back memories of when I first sat down with myself and contemplated 1 micro volt is one millionth of a volt...? Let alone Microamperes! Are you kidding me? Thank you for all you do!
Some of this takes me back to your video #88. I used that circuit to find bad coax on the job when troubleshooting. The reason I remember that video is I use it to refresh my brain when I need to use that inexpensive TDR to find bad coax on the job. The video is in my saved for reference set of videos on youtube. That is now true for all your VNA videos also. Keep on expanding my knowledge base. Thanks
The last analyzer I used was an Agilent PNA and wow, what a nice piece of equipment for over $30K. Being a ham and an experimenter I sorely missed having access to even the old "antique" HP analyzers. When I saw the nanoVNA being offered I figured I'd invest in the ~$50 for what I thought was going to be a cheap toy. I was wrong. The only complaint I have with it was the poor documentation and the touch screen; however, through your videos and others like it I'm able to realize the potential of this device. The menu screens are not intuitive and having you walk thru the set up process is a great help. Some of the screens don't match mine eg. it doesn't have marker peak search probably because I don't have the latest firmware. But, no matter I was still able to use it to measure a piece of coax. Just for giggles I took one of the cables that came with the device mainly because I didn't want to unbox a long length of RG-8U and measured it. I set the stop frequency to 500 MHz and the velocity factor to .66 and lo and behold once I converted from meters to feet the measurement was spot on. The touch screen drove me nuts in the beginning. You definitely need a stylus to access the menus. I managed to find the one I had for an old tablet and life was good! I really appreciate and enjoy all your tutorials. You really have a knack for clearly explaining what is really a complex concept. 73 de N1ABE>> Ps. Your lab is a hell of a lot neater than mine.
You know, it strikes me that RF is *very* similar to audio engineering, but combined with core EM principles. In my 10 years of professional work in audio, I came away with a primary insight: the most important element in getting a good recording is the room itself. "Room acoustics" deals with things like cancellation of standing wave modes and problematic reflections. So anyway, just a tidbit for folks that are technically interested in audio; you can make the leap into RF stuff no problem because it equips you with the core intuition, very very nicely.
@@danmoretti8898 It is! Also the same as, say, engineering a car's suspension. Those pesky waves show up everywhere :) I think the main thing that's different with audio is that you very rarely have to worry about transmission lines so much because the wavelengths are huge relative to most of the parts. Audio synthesizers specifically have a lot of concepts in common with radios and are a good place to start learning the concepts because the components needed and test equipment requirements are far lower and less expensive.
@@bundo13 Cheers! As you would imagine based on your example of the car suspension, there are plenty of energy buildup problems in audio! The rest of my post here is probably stuff you could have guessed, but I wanted to share anyway. As a rule in audio, transmission issues come into play anytime transduction occurs. So 1) capturing audio (particularly in stereo) and 2) playing audio through speakers. In the former case, phase coherence becomes a really important thing to have a handle on with mic placement. In the second case, we often run into problems with resonant cavities (rooms). If your room is too small, it becomes a high pass filter due to bass frequencies not being able to fully propagate through a cycle. This makes for a dishonest mixing environment, and your mix will sound weird on playback in most environments. HF buildup is a huge problem in small rooms as well. In auditoriums, propagation rates begin changing in a manner that's thermally dependent, which is why live sound sucks for the first couple of songs. The crowd brings a substantial amount of heat. Until thermal equilibrium is reached, the EQ is completely off. So anyway, longitudinal transmission through a gaseous medium is really where transmission stuff gets wacky. Between synthesis; microphone placement; mixing; and live acoustics, audio engineering is a very broad and interdisciplinary process. But again, its just the same as any other type of engineering in that sense.
@@danmoretti8898 Fascinating! Thank you for posting all this, I am certainly no expert in audio or RF but I learned at some point to post what I think I know on the internet because writing it out helps me solidify it in my own head. I should have clarified that I was thinking of the electronics. Audio frequencies propagating at very high speeds in electrical circuits have huge wavelengths, but can certainly come into play when at the speed of sound in air. So I think that reflections and other transmission line effects can mostly be ignored when designing the electrical side. Not to say the electrical side is trivial of course, just different things that are the big factors in overall quality. I have to admit the first thing I was learning about where I feel like I really started to get a handle on wave math was when I was learning about transmission line speakers, because they're just so darn cool. I found it much easier to imagine speakers and sound waves when thinking about stuff because those things are so much more familiar in our day to day lives. I often think about antennas as speakers and impedance matching circuits as horns still! I also use these as analogies when trying to explain what I think I know to other people as well. I find it much easier to imagine how a shout echoes off of a cliff wall than about how an electrical signal reflects off the end of an open transmission line. So I appreciate your examples, I've never messed with audio design at such scales. It's very interesting, and I feel like the more ways we have at looking at the same fundamental concepts, the better we can understand it. Interesting tidbit is that Bose has even worked on electromagnetic dynamic suspensions for cars. I may not always agree with the value prospect of Bose's products, but I've always respected their engineering!
I remember RadioShack had mini electronic note books that were beautifully hand written for text and schematics, your writing reminds me those tiny booklets that dates back 30-35 years ago !!!
Great lesson!! Also how the NanoVNA's low cost can yield good measurements versus a 20K VNA!!! Be great for EE class labs where super expensive instruments were handled by the instructor (1971 for me ) and how "hands-on" lab work is so much more instructive. The instrument automation expedites the time and attention factor for instructional learning. Many Thanks!!!
They are evolving so quickly eventually SOON a NanoVNA will do what an 8753ES will do, which costs 7-8k used in ok condiiton. Once they have a reversible test head it'll allll be over.
Silas Marner considering the price point, the nano VNA offers value for education, and hobby use. However, the performance doesn’t come close to a 8753 or a field fox: span, dynamic range, points, coupler,....
I really in joy your your videos I have watched most of them and always lean something I'm 66years old and just get started in ham. I plan on testing in Feb 2021 to test so I'm trying to get as much knowage as posable be for testing and getting on the air and you have help greatly. Thank You Keep up the Great videos
Try this with 75ohm cable. The rotation should be centered on the new characteristic impedance rather than the center of the chart. This trick is often used in splitter networks to transform when 50ohm is split into two 100ohm lines. Rotating round 75 for ¼wave will transform the 100 back into 50ohms. Great video. Very clear.
you could always just normalize to a 75Ohm load during calibration to get around this, but the firmware isn't setup to tell you the correct calculated impedances from this normalization. If the NanoVNA firmware developers are reading, a feature to change the impedance normalization of the chart after calibration or before the calibration so the calculated impedances would be correct would be great.
Another EXCELLENT presentation Alan, You've convinced me to buy one. I've always wanted a TDR. In the mid 70's I also attended Training on the 7704 O'Scope and all its plugins, to include the TDR PI. I was AMAZED at the perfection of GR connectors, the pure GARBAGE of "UHF" Connectors, plus the fact that you could observe a glitch in a half-inch coax when you squeeze it with your fingers. 😲 Fast forward about 10 years I was working in Saudi Arabia where my office had a flunky from the "Wiring Department" run cable for a 10BASE-2 network. Nothing worked! I borrowed a portable TDR and found opens at almost every computer in the network. Because...and get this...the flunky didn't know that he had to "crimp the center pins." 🤣😂🤣
I am building a 60 foot length of RG-8X with a PL-259 on each end. This was very helpful. I had roughly measured 60+ feet (middle of chest to finger thumb hold = 36 inches). I was learning how to use my Nano VNA H4 to measure the length. You made it very easy to get an answer. I used the Transform with the linear format on Trace 0. The answer came up at 19.3 meters using 50 Khz Start and 230 Mhz stop frequencies. I had to use an 80% VF to get this number. Then I used a tape to measure the the length which came out as 12-5 foot lengths or 60 feet plus 40 inches. Right on 63'4" or 19.3 meters. I post as feedback on the 80% velocity factor, for the RG-8X. Mine was labeled Davis RF / Div of Orion Wire. It is new. I then measured the SWR and came up 1:1 from 140Mhz - 150Mhz and 420Mhz - 450 Mhz. I will use the to feed my 2M - 70cm J-Pole. Thank you for some great videos on the Nano VNA and the science behind what the instrument is doing. The Tiny SA just arrived and I will be looking at your videos on this. I really appreciate your notes. I punched my Tech and General last March. Very helpful to this new Ham.
Alan, this video might be one of my new favorites that you've produced. I absolutely love how you're able to teach complex subjects by putting them into context that non-EEs can understand. Brilliant! Thank you!! 73 KA3YAN
@w2aew Much appreciation and respect! I really like the whole series on measurements with the NanoVNA. Please keep making videos in this series to fully exploit the NanoVNA's capabilities. I recently purchased one, but getting details on it's limitations (101 sample points in the bandwidth settings) and how to use it (best settings for stop frequency vs resolution of length) was difficult for me to locate, until you started this series. This series and the extras (Smith Chart, transmission line effects on observations...) is GOLD! With your formula for setting the stop frequency for cable length, I suppose I could find the velocity factor of an unmarked cable after measuring a shorter length of a sample piece of the coax.
You should consider using it in conjunction with a PC and nanoVNA saver; this will allow you to use practically arbitrary sweep point setups with more accurate averaging capabilities.
Just got my nanoVNA a week ago and was wondering what I could do with a Smith Chart. Off to measure my feeder line loss now :) Thats a great explanation of how to use the NanoVNA - Thanks w2aew.
Thank you w2aew for great videos. In the demonstration of forward (or backward) waves, the negative amplitude means reverse movement w.r.t. positive amplitude, but they are moving in the same direction.
Great vide4o. Ran off to Ebay and bought one of these (US seller, with case). Looks like a nice little box. Much easier than my HP TDR for sure plus it has the advantage of me not having to remember how to do a smith chart every time I use one. Thanks W8DKM
Thanks for taking time to help answer questions. This looks like an awesome little tool. Nice to see a real "live" Smith chart. This is an excellent aid in understanding rf.
Extremely educational and understandable , thanks! I've just ordered today the nanoVNA -F , so it's time to get back to the school desk before it arrives in a few weeks time! 73 ! Linas LY2H
Hi Alan, Was taking a break from practice exams for my online Extra test session Monday evening and noticed you uploaded this video. Much of the video is in questions on the test regarding impedance for 1/2 and 1/4 wave transmission lines. I now have them straight thanks to the video. Stay safe. 73 WB3BJU
Thank you Allan ! I appreciate so much your videos. I wish I could have this illustration when I was studying at the University. I learned this concepts with ugly math as you said!
Thanks for really helpful series of videos on the NanoVNA. Like many radio hams, I bought one to experiment with, without knowing anything about them. The more I watch, the more I (slowly) begin to grasp how to use it and what a nanoVNA can do. Can these instruments measure how a home-made rf choke is performing or what frequency an antenna trap is working etc? It would be very useful if it did.
You make this so easy to grasp. Your presentations are incredibly organized and smooth flowing. You obviously know your stuff. How I found you is that "The IMSAI Guy" referenced your videos in one of his in regard to your making dummy loads. AD6AE
Thanks for the video. I got a NANO VNA last year. Great little bit of test gear for the price. Helped to set up my dipoles and inverted vee instead of just an SWR meter, I knew if I need to shorten or lengthen them. I'm going to try measuring the length of a piece coax. How to amaze people with technology if they say you need a tape measure. I guess this is how a cable fault locator works. G4GHB
Thanks you Sir..I like you video's and explanations.Very Informative.I learned aload from you sir.Can you make a video how we tune the phase harness for a 1x2 array antenna matching circuit.Thank you sir.
So if you have access to a PC, you can use a piece of software called NanoVNA-saver to do this too. If you increase the number of segments you can get around the 101 point limitation. It even will calculate the coax length and you can select the coax type or manually enter the velocity factor that way.
I've recently discovered your channel and truly amazed by the quality of your videos! I started from #1 and planning to work my way up to the top :) May be in one of your future videos you can explain what complex impedance means applicable to the antennas? For example an impedance for a half wave dipole is 73 + j42.5 , but what does it mean? Are we always supposed to see reactance in the resonate antenna? Thanks and please keep up the good work. 73! Victor, PA8MM
Thank you - I hope you enjoy my series as you work through them, and please excuse the poor video quality and shaky cam on my early videos. I do talk a bit about complex impedance in later videos. Note that the definition of resonance is the lack of reactance (only resistance). Resonance does NOT always mean 50 ohms!.
‘Hope you learned a little something today’ pff… who are you kidding… Excellent content as always Alan! Any recommendations for a bench top signal generator in 2024 that doesn’t weigh 30kg? Something suitable for testing receiver sensitivity and calibrating AD83xx based power meters. I have an early RF Explorer sig gen but it’s limited to 24MHz and up. Can the TinySA Ultra sig gen functionality replace an HP or Anritsu? Should I look at constructing reference RF sources at key frequencies and then attenuate? Your input would be most welcome. 73 John
Thanks for this systematic explanation of measuring coax length and distance to fault. It is very easy to follow. I have followed the process to check a 100 ft. (30.5 m) coil of RG8X. On the linear scale, sweeping from 500Khz to 125Mhz with the transform function set up in low pass, I get one single peak at 14.65m . If I flip the ends if the cable I get the same figure. Is my nano vna-h defective? I have calibrated before. starting.
Hard to believe such an inexpensive piece of equipment is able to produce so much information in the right hands. Mine will be here from R&L next week. Wonder if it uses the AT Mega 328 Microcontroller? No tellin how far these will go as VNA's, or how big the screens will get.
Thanks for this video. As I see it you can have a Los SWR but not Resident. Or my thinking wrong. And it's gotta be better than my MFJ259. Been off the air for 20 plus years. 73 KQ4CD Paul
These little Chinese whiz-bang devices provide amazing capabilities, for the price...but the MENUS! I think I could set up an improvised TDR, with a scope & pulse generator, to do this, in less time than figuring out, and working through, the menu!
One could measure the velocity factor of the coax before starting these measurements. The "assumed" can be way off and its very easy to do. A good tape measure would then be the primary standard.
How would you do this? I would like to measure the velocity factor of some material I have. The manuf’s spec seems to be off. I calculated what I believe it to be, but it would be nice to verify with a measurement.
I watched a few other videos on NanoVNA and parameters, and you clearly know the details of what you're talking about. How come you don't have a "Thank you! $" button under your videos?
Can you explain or link resources to something that explains what the "Low Pass Impulse" transform option actually does in signal processing that enables us to see what we want better here? I've found in the manual on page 14 says what we are doing is simulated operation as a time domain reflectometer (TDR) to measure the distance to a power reflection (short or open) when selection the "Low Pass Impulse" transform option: (nanovna.rf.pl/Manuals/NanoVNA-User-Guide-English-reformat-Dec_9-19.pdf ). This explains how to get the outputs we would want for this measurement in a simulated TDR fashion, but what is actually going on under the hood? Do you know a specific resource myself and others might find helpful?
I was wondering if you might clarify something, I have been taught that the coax length should be one half wavelength of the frequency that you're using adjusted for velocity factor in order not to create additional SWR. So are you saying that this principle is not accurate?
Explained and a way the common man can understand, thank-you. I fear I have unwittingly ordered a cheap clone, how will I know if it's good or bad?....or will it be obvious. Bear in mind I'm learning so not much experience.
Great video, thanks. I have probably the original version of the NanoVNA, so I wonder if it operates differently. Using your exact procedure to measure a 15m length of RG58A/U, the Linear trace is flat...no peak as you got. However, if I turn on the SWR trace, I see a small peak at about the 15m point on the marker. This is an open (unterminated) coax. Any idea why it's not working? Thanks much!
This is really useful at the moment, I have the NanoVna and was searching for this very subject. Thank you so much. I have a long piece of coax that has a VSWR problem and I'm sure this will solve the issue or at least let me know where the fault is along the cable. Thanks again. Andy. PS just Subscribed and Bell'd ( is that a verb?)
Very neat writing, print, mine's horrible and when it gets older I am at loss to read it. And at 69 yrs old it's just getting worse so I record and transcribe my " notes" if I want to archive them usually nothing worth saving.
Short version: I didn’t want the small screen on the original. That left the H4 vs the F to get 4” screen. It seems the H4 has a bit more active development behind it vs the F. But the F has a metal case which is nice. So, a bit of a tossup. I went with the H4. The new V2 goes to higher frequency with better performance, but it is still in its infancy and not widely available with a case or large screen yet. This may be the better choice in a few months once large screen, enclosed versions become available.
Hi Alan At 12:05 h min in your video: If you now calculate very precisely and meticulously: 299 792 458 m / 315 Mhz / 4 = 24 cm. But the short piece of transmission line is only approx. 18 cm long. Where do you think this discrepancy comes from? Is that just the level of accuracy to be expected from a $60 device, or do you see the cause elsewhere? Your videos are always great - what of the finest on the subject of electronics on RU-vid!
Your calculation doesn't take into account the velocity factor of the coax. That explains the difference. Signals travel more slowly in the coax vs. free space.
@@w2aew I've deleted my previous answer, because meanwhile I did some further experiments - and you are (as expected ;-) right: I took a RG-174 cable with a known velocity factor (VF) of 66% and than multiplicated the NanoVNA result length with this VF (x 0.66) and voilà - I got a calculated cable length of 206 cm - and the *_real_* cable length almost exactly 206 cm as well.
Thank you for explaining how to measure the impedance of a coax cable. Would you measure the parallel wire (Ladder line)? I did the same thing for tha ladder line using 1.2mm wires taped together without a spacer. It seems to be more or less 45 to 50 ohms. Is it correct? Or I am doing something wrong.
