How not to damage your NanoVNA when measuring SWR

[@athgt6630]

That feeling of satisfaction when, for once, you have watched the right video *before* doing something dumb.

[@joesmith-je3tq]

Glad you feel it helped. Hopefully it's prevented a few from becoming damaged.

[@freeloader700]

I had no idea you needed to ground out the coax before connecting. Glad I saw this before my VNA arrived.

[@williamselzer1722]

me too, thank you

[@teslar1]

One of those evergreen videos that is very relevant today. Thanks for this I’ve just ordered a new not so cheap vna and I’m now fully aware of what not to do with it

[@handyman7147]

I am getting my nanovna in a few days. Good that I saw your video. I would have killed my vna. Never thought of the static build up. Thank you for the excellent info.

[@daviddevillers6790]

Ordered a NanoVNA and TinySA a while back. Thanks for helping me ahead of time from damaging these instruments. Always appreciate your videos, Joe!

[@qzorn4440]

for a beginner it is no surprise to damage something without an educational video like this one to get started on the correct foot 1st. 😎 thank you so much and I am new to the NanoVNA.

[@joesmith-je3tq]

Glad you found it helpful. Have fun learning your new VNA.

[@vincei4252]

I guess the downvote was from the guy that climbed up his antenna then blew his NanoVNA?

[@judd_s5643]

I’m new to your channel and this is my first video I’ve watched and I must say that your presentation style is spot on. From this side of the camera you come across as if your talking to the viewer and not a room full of people. Very personable.

[@joesmith-je3tq]

Thanks and enjoy your stay.

[@nathanhaltman7235]

I have a high power AM broadcast station near my station. If I connect my HF beam to a power meter, it reads about 5 dbm. Therefore, I always use a band pass filter and 6 db attenuator before measuring the HF beam SWR with a HP 8753e.

[@MickDownUnder]

Nice insight Joe, as always. Maybe worth pointing out that static build up in a *DC grounded* antenna system can be kept under control by providing a path to ground (earth) via connection of the outer shield of the coax. I keep any wire (including coax) running into the shack/lab grounded if not in-use. We in Australia rarely see the static build up that you guys have to deal with in the more icy parts of this rock.

[@ebaystars]

I keep an eye on the weather radar in thailand by the gulf, 1 too many beers and a sleepy afternoon could be FATAL

[@denis_w1wv131]

Well done Joe, very valuable experience you shared.

[@TheMainsheet]

Thank you! for the clear concise explanations, very well done

[@PH2LB]

Again a very interested video Joe. You have put another project on my "need in the shack" project list : "Joe Smith NanoVNA ESD Saver"

[@joesmith-je3tq]

I suggest the Lex NanoVNA ESD Saver.

[@g0fvt]

I just ordered some SMA connectors to build a protector for my NanoVNA, I knew of the issue so had held off from using it for sweeping HF antenna. Your video gave me the kick to do it. Many years ago I killed my frequency counter with a similar mishap.... rare and expensive prescaler destroyed.

[@joesmith-je3tq]

I've been in the habit of grounding anything, including myself before touching anything ESD sensitive. Coax makes a very good capacitor, low ESR and could really do some damage.

[@KallePihlajasaari]

@@joesmith-je3tqI Is there the same danger from stored charge if the antenna connecting/matching network has a DC short? I recall placing a 90V Neon bulb across my 27MHz CB radio decades ago and watch the approach of thunderstorms. It would blink at an increasing rate until the rain started and let the wet antenna insulator drain the static. I did this because the PL259 would arc over and keep snapping in my bedroom as it exceeded the air gap discharge voltage so a few kV is easy to reach. It took me quite a while to first find the source of the erratic sound, the antenna was mostly unconnected when not in use as lightning induced damage is common during Highfeld thunderstorms.

[@radiotests]

Simply awesome. I was trained old school Navy when just looking wrong at ESD parts would boil them. We even had a six week course on how to save the Navy millions on blown SAs and cards covered in epoxy that were the getting ends of every search radar. I do wonder what kind of values I would need to consider for protecting the LiteVNA testing out antennas in the GHZ range. all my radios are pretty much VHF and higher. Thanks Joe!

[@joesmith-je3tq]

Personally, if this is something I were doing, I would just follow good practices rather than giving up performance. The LiteVNA does have a clamp directly across each input. I removed them on one of the LiteVNAs I have to see if we could improve the performance at all.

[@TheRayDog]

Thanks for posting. I'm using the short calibration piece from the nano to discharge.

[@earlyadapter643]

It's amazing how the LNA can be calibrated to measure SWR through an attenuator, i haven't seen or thought of this before. It will deteriorate a bit the accuracy but it's well worth the protection.

[@joesmith-je3tq]

The attenutator in of itself would not provide a lot of protection. If you followed this video, we worked it through four different levels. Even then you could still damage your VNA. The other potential problem is I was assuming the hams are using very low frequencies. The higher you work the more critical the component selection, layout.... would be.

[@earlyadapter643]

​@@joesmith-je3tq I work from 20 m up to 2.4 GHz. However in the world of microwaves, the cable is less likely to store a lot of charge :)

[@joesmith-je3tq]

@@earlyadapter643 20 mHz is 0.02 Hz. I've had people enter m in place of M in my software and ask me why there is a problem. lol. My last set of videos I have been playing with microwaves. Rather than cables I've been using waveguides. In part 3, I was experimenting with some 3D printed horns. While working without a wrist strap and managed to damage an amplifier. Knew better but felt that with the horn sitting at DC ground and the VNA and extender also grounded, the risk was low. Bad mistake. Anyway, my point was adding protection for higher frequencies is not as simple as for lower frequencies.

[@earlyadapter643]

@@joesmith-je3tq Thanks, i will certainly have a look at your videos about microwaves and hollow guides. A colleague around here made a beacon for around 70 GHz and also 130 GHz i think, with a Schottky diode at the intersection of different hollow guides, all locked to a GPSDO. By "20 m" i meant meters :) My VNAs are all still alive.

[@joesmith-je3tq]

@@earlyadapter643 Ah, ham speak. Consider not mixing units when defining a range of frequencies. I can't afford new test equipment for my hobby and picked up an old VNA a while back. Upon inspection, it was apparent that the previous owners had exceeded the input specification. Judging by the damage, it was connected to a power amplifier. In this case, a simple attenuator would indeed have saved it. That being a higher end system, I expect it sat in a lab and I wouldn't expect to see this to happen. With the low cost VNAs being popular with the hams, I don't think you can count on that. I posted a video of a ham who literally placed the VNA between the antenna and their radio to show how to measure VSWR. Have a look: kzbin.info/www/bejne/qnSrcpRjqM-ambM I think the best protection starts with education.

[@DavidLopez-bz4rj]

Thank you for the video, Joe.

[@murrayri]

I have just became aware of your channel. You now have another subscriber! I like your various termination PCBs. Did you make them or are they commercially available? I also tried to download your NanoVNA software but get a 404 error.

[@joesmith-je3tq]

Welcome aboard. While this channel has nothing for sale, I have seen others making similar boards which may be for sale. I would just check around. I moved my software from Github to Dropbox about a year ago as many people had problems sorting out how to use it. You can find the announcement and link here or use the link to EEVBLOG and follow my signature. kzbin.info/www/bejne/rnW9oYSJaLSobNU

[@worroSfOretsevraH]

How does a ham radio with a very sensitive front end, not get damaged when you connect a charged antenna wire to it? (or leave connected all the time)

[@rocketman221projects]

The receiver will typically have some protection in it, but you can still blow it up by connecting a charged coax to it. You should always ground a coax before connecting it. You can get coax switches that will ground the ports that are not selected. It's a good idea to put a bleeder resistor on the antenna or use a DC grounded antenna to prevent static build up.

[@MidlifeRenaissanceMan]

@@rocketman221projects I’ve always used some sort of feedline / matching transformer or inductor where the centre of the coax is at DC ground and the antenna is also at DC ground. Firstly it makes the antenna much quieter, and I have never seen any static discharge on the antenna or feedline.

[@HumanTimeMachine]

Dumb question What if you were to short the antenna center connector and braid with your thumb. Shouldn’t that rid of any residual static and capacitance?

[@joesmith-je3tq]

I wouldn't recommend touching contacts due to the fatty acids in your skin's oils. Not to mention the other stuff. But yes, your hands even dry would provide some discharge path. Now if it would bring it to a level that wouldn't damage a sensitive device, hard to say. Too many variables.

[@kostaskritsilas2681]

A couple of ideas: 1. To have the Nano VNA inline between the antenna and power amplifier, try using a circulator. Put the power amp into the input, the antenna into the direct output, and the nanoVNA onto the second output port. The second output port is available at -10db and -20db attenuation levels. Also add an inline dc block to the second output port, and maybe add some inline SMA attenuators, which would be dependant on the power levels of the amplifier. You should calibrate out the circulator, dc block, and any attenuators. It would be acceptable to connect the nanoVNA onto the circulator when you want to check/measure the power amp/antenna system using the second port, and then just terminate it when the nanoVNA is being used elsewhere. 2. You can use a gas discharge spark arrestor and follow it up with a RF transorb/TVS. The gas discharge tube can take out most of the energy, and the RF transorb/TVS can take out anything that makes it past the gas discharge tube.

[@Basement-Science]

People hooking up a transmitter directly to a VNA remind me of people that try to "measure the current of their mains supply" These are people who dont even know WHAT they are trying to measure, but are doing it anyway.

[@felixcat4346]

Thanks for posting, always interesting.

[@DavidLopez-bz4rj]

My NanoVna was connected to a high static antenna and it survived very well, it zapped me through the vna.

[@solarflare4259]

Does the Nano VNA have no input protection built in? I would think it does but definitely another layer of protection would make me sleep better. Thanks for posting!

[@joesmith-je3tq]

Well, I guess that depends how you define it but I will say mine has no type TVSs or other clamps.

[@solarflare4259]

@@joesmith-je3tq Thank you! Good to know...

[@aronhighgrove4100]

Are the (unpopulated) filter boards you used around 17:26 available for purchase somewhere? Or are they purely to build attenuators?

[@joesmith-je3tq]

Those are my SOLT standards as well as they are used to measure components. Sorry, there is nothing on this channel for sale.

[@michaelst.angelo423]

Enjoyed the instructive video. Is the suppressor schematic and parts list documented anywhere?

[@joesmith-je3tq]

The idea of the video, as I mentioned in the video, was not to give anyone a turn key solution but rather explain the problems and potential ways to mitigate it. The problem as I talked about, there is no one size fits all. You have people plugging them directly into their PAs output or placing them on a BIG capacitor without discharging them. I would say the best solution is to learn how to use the device before you go connecting it to things you perhaps shouldn't. A bit of knowledge will get to a lot further than any type of clamp.

[@Yannis..]

Thank you very much for the info you share with us !!!! Just wondering if placing a high value resistor (maybe 100k) across the coax to constantly discharge antenna system would be enough to protect nanoVNA in case I forget to short cable before measuring ??

[@joesmith-je3tq]

Sorry but I really don't know. I assume you are suggesting a 100K ohms at DC. Have you characterized this resistor and it's mounting hardware over the frequency of interest? Is the return and insertion loss acceptable? Is this resistor and mounting hardware able to withstand the voltages and power at the frequencies you apply to it? If you are only asking if resistors can be used to drain off charge, then yes. Most power supplies will have bleeder resistors for safety. It's common practice.

[@Yannis..]

I am setting up my first amateur radio station so I will try bleeding resistor to also protect my gear (below 30MHz / 100W) keeping in mind the parameters you mention. I have some electronics knowledge but nowhere near your level and thanks again for your videos !!!

[@joesmith-je3tq]

@@Yannis.. What is it that you hope to achieve by connecting the Nano to your antenna? Is there a particular problem you are trying to solve? Just wanting to play with a VNA and your friends are connecting theirs to antennas?

[@Yannis..]

​@@joesmith-je3tq I just plan to install a multiband wire antenna for HF either end fed or dipole (trap or fan) 4-5 meters above a flat concrete roof and a total 10 meters above actual ground so I ordered a nanoVNA to help me during tuning procedure. I have played with VNAs and RF measuring equipment 25 years ago at the production line of long haul microwave links adjusting radios including space diversity receivers but unfortunately never involved at RF design and since then I changed career to IT.

[@joesmith-je3tq]

@@Yannis.. Wire antennas have been in use far longer than VNAs have been available. I wonder what you feel the benefits are of using a VNA to help tune your antenna compared with other methods?

[@Sonny_Eclipse]

Very good information, I wish I had the expertise to design and build one of these. I was disappointed that you did not provide a schematic and parts list.

[@joesmith-je3tq]

Sadly you completely missed the point that there is no one right solution. I too am disappointed.

[@victorb22622]

I never thought that nano vna could be damaged,but then i have to have these much other stuff ,what you shown.but again question arise is ,even touching finger to rg8 cable change the figures and you are attaching these others devices and connectors in between antenna and nanivana.

[@joesmith-je3tq]

Sorry but the wording is too poor for me to understand what you are trying to convey. I would imagine most RF equipment like the NanoVNA can be damaged from ESD events. Much of my equipment can also be damage by having a DC bias.

[@pa4tim]

The blow up by antenna measurements is not because they use TX (I hope, it would be pretty stupid). The problem is there is a huge build up of static on big antennas. But I think you talk about this. But to be sure (language barrier) I had a 50 meter dipole with open line feeders. I have seen sparks jumping over between the open feeders that were about 4 inches apart a few ours before a thunderstorm but also on hot days with not a cloud in sight. And fiddling around with the tuner I sometime got zapped by the static. I since that happened to often always had 100k resistors from each feeder to ground. An other point is that the signals for lets say 20 meters where you have set the VNA to, are low, but on the same antenna are the signals from DC to daylight and on for instance on 500 kHz to 1,5 MHz there can be a huge AM broadcast signal. That can overload your VNA. If I measure bigger broadband antennas I use an external directional coupler or bridge or use a f,i. 10 dB attenuator

[@joesmith-je3tq]

I was amazed with some of the posts on groups.io. This is what prompted me to post this video. I suspect there were hams that saw two connectors, knew that their simple SWR meters went in-line between their antennas and radios and promptly hooked up their VNAs expecting similar results. After all, even the ham radio store we bought the LiteVNAs from advertises them as antenna analyzers. Poor hams never stood a chance, nor did their VNAs. A few asked about trying to measure their antennas with local radio stations causing problems. I showed at one time using an external coupler and amplifier to increase the signal level. Most just seem to want to measure SWR, which is easy enough without a VNA. We had a thread running on EEVBLOG and I showed a simple in-line power meter that could also measure SWR. Fun little project. kzbin.info/www/bejne/gHnWmJWrbMelj6s

[@thingsbeensaidanddone.2378]

Hi. I am On7dbr. Thanks for video! I just have a small pass trough box. In that box you can but anything you want. I make just one turn coil and it is a pass for 145 Mhz. On DC it is a short. So there is no esd because it discharges any load all the time. Gr Reza

[@ronsampservice3066]

YEP! Gotta check how big the signal is with a VOM or a scope and ALWAYS use an attenuator, and start with the largest attenuation and work down till you can measure the signal. You can find info online to build a signal pickoff too. So the signal your vna, scope or whatever, sees is 1/10th or 1/100th or whatever of the true signal.

[@jertres2887]

I get 4 db for the pi attenuator instead of 3, using an online calculator. But that’s pretty close..

[@MrDwadi84]

Hi Joe interesting video, I have question if it apply to even to latest Nanos, I just bought latest V2 revision with more measuring points and extended frequency range. Great that you wanna provide this method to public - very good idea. I think you also could contact with authors if this antenna analizer in order to implement such protection to latest designs.

[@joesmith-je3tq]

Questions end with a question mark(?). I think you want to know if you can damage the latest V2 from similar test cases like I mentioned in the video. I would imagine that ANY test equipment can be damaged with the right operator! The VNA is not an antenna analyzer and has many uses in the hands of a designer. Adding protection like I show would hurt the performance. As I stated in the video, there is no single solution. Again, it's best just to use your head and follow some simple practices, like learning to bleed off excess charge before connecting any test equipment to anything. Not connecting to things you should not. Learning about what you are trying to do, before you attempt to put it to practice.

[@MrDwadi84]

@@joesmith-je3tq sorry don't be rude and I am also not native english speaker mixed witch dyslexia - it is normal for me that I often fix my posts with editing. Back to the topic sorry for wrong words about naming VNA antenna an, I found that many HAM channels that I sub. name like that, maybe it is caused by them because it is their main purpose to use it like that. I know also that "Nano" can do many more - so agin I am sorry about my small knowledge ;) I always tried to extend my knowledge in many things that I like to do. I wanna take HAM exam, but due to covid in my country (Poland) exams are closed for now so I use my free time to learn beyond common questions from exam, that haven't changed for years, maybe this is reason that many HAM operators not develop skills in this matter, many people from my country thinking that they buy cheap Baofeng and use this as PMR radio and use its full power that much is much more than regulacjon allows. So I gave you a sub because I think I could learn more that only using the radio to pushing buttons. Thanks for understanding.

[@joesmith-je3tq]

@@MrDwadi84 I'm sorry you feel that I am being rude by trying to help you learn how to ask your questions. This is a skill we all can benefit from. You will find me to be direct as well as typically data driven. Try not take it personal. I think I mentioned during the video that I played with radios in my youth and learned a lot from reading books and playing with RF circuits. Eventually I lost interest as I became more interested in electronics and digital design. If you like electronics, there are several very good channels to join that will offer much higher quality content. I would imagine there are some that combine your radio hobby with electronics. Try youtube's search. I've had people tell me that they use the old HP8753 series for looking at SWR. Odd in itself but I don't think I have heard one of them tell me it was an antenna analyzer yet. But I keep waiting....

[@MrDwadi84]

@@joesmith-je3tq maybe it is common mistake by removing from Nano this other things that we could take benefis. For me this point that you stated - about static discharge is courious cound you explain this bit more? What antennas was common common reason of this problems. Wire antennas, verticals, brams, or maybe Yagi-Uda's IT is just puree curiousity... I ordered some socket adapter with gas tube to ground my vertical HF antenna to 6m grounding pole - Is this any safer or should I use your method to be more secured? Also your one piece calibration standard is great, is there any possibility to buy this from you? - it looks very handy, much better than that I got with my Nano V2.

[@joesmith-je3tq]

@@MrDwadi84 I doubt a direct hit by lightning will care too much about the type of antenna it hits. I think the safest thing to do would be to follow some simple guidelines when using sensitive equipment. I would have thought that having some sort of grounded suppressor inline would be common practice. Depending on the transient, it may not be enough to save what ever is hooked to the cable. As I mentioned in the video, most of my experience with ESD surrounds the HBM for EMC testing which is a lot different than the transients you are asking about. There may be some good books available on the subject. I've never researched it but I am sure the commercial stations have a good feel for it.

[@SpinStar1956]

Hi Joe. First-off, thanks for all the videos, insights and techniques that you have presented. Just getting back into all this RF and the instrumentation is fabulous and affordable. Question: Would it be reasonable to use a NE-2H (or several) as the GDT since they fire around 65 volts? If so, it might make it a little more accessible for people building these protective devices. 73...

[@joesmith-je3tq]

As I mentioned in the video, I've seen them use the old neon lamps as a clamp. Also as I mentioned, the type of clamp you design would be dependent on your circumstances which includes not making one at all. The goal of this video was not to provide a generic clamp that someone could produce but rather give some ideas on what would be involved in designing one.

[@departament5]

Can I use something like CA35RS Coaxial DC lightning protector to protect NanoVNA ?

[@joesmith-je3tq]

As I stated during this video, there is no one size fits all answer. The goal is to show viewers how to go about designing a protection circuit and some of what you may need to consider, not to offer a recommendation on products or provide a turnkey solution.

[@joesmith-je3tq]

Maybe read this thread where a few hams chime in on the discussion. nanorfe.com/forum/ESD-safer-circuit.html

[@WogChilli]

I'm a new hobbyist, getting my license soon. I wish I understood even half of what you were discussing. Basically what I did absorb is; static bad for nano. Is there a way i can earth the antenna before i hook it up to protect the nano? Conduct to ground ie. Water pipe?

[@joesmith-je3tq]

As the video talks about, there are a lot of variables. Applying a low impedance path from the center conductor of the coax to its shield before connecting anything up I would expect is common practice.

[@WogChilli]

Would that be like placing a resistor across the conductor and the shield?

[@joesmith-je3tq]

@@WogChilli Resistors can certainly have a low impedance.

[@MikeG-js1jt]

Why are they even involving attaching the radio when testing an antenna? such as sweeping an antenna for swr?

[@joesmith-je3tq]

You would need to ask them. Here is a video where a ham is teaching other hams the proper way to use a VNA. kzbin.info/www/bejne/qnSrcpRjqM-ambM

[@michaeld4502]

Which nano version would you recommend for measuring Omni and Yagi in the 902-930 MHz range? Great video.... Wish my eye sight was good enough to make this device...

[@joesmith-je3tq]

Assuming you just want to measure VSWR, maybe consider a good VSWR meter? At a GHz, you could make up a coupler and use your scope. If you are trying to measure radiation patterns, maybe a portable SA and your phone for GPS tracking? These low cost VNAs are a very good tool to learn some basic concepts. If you want to experiment above 300MHz, I like the V2Plus4 but they are seldom in stock. Another recent option is the Lite. If you want to experiment below 300MHz and would like to use it for narrow band work, I would stay with the original NanoVNA. I have not made a review of the Lite, but I did for the V2Plus4. kzbin.info/www/bejne/jpK8c6OGeNRkp80 Of course, if you can't work with a squarewave drive, you will need to open your wallet. kzbin.info/www/bejne/r2fMgId7ipuNsNE

[@DeanDubovac]

Hi Joe, greate video, unfortunately I manage to burn my nanoVNA before watching. :( Do you seel this protection device as kir, or can you share BOM or PCB design? Thanks.

[@joesmith-je3tq]

The goal of this video was not to provide a generic clamp that someone could produce but rather give some ideas on what would be involved in designing one.

[@DeanDubovac]

@@joesmith-je3tq Thanks. I will definitely try to do it.

[@williamburrowes1714]

Hi Joe, Great video. Can you tell me what software you are running and can you supply a link please? Thanks.

[@joesmith-je3tq]

Take the time to read the description.

[@brandonjc6695]

Any interest on running the Aneng AN870?

[@joesmith-je3tq]

If you look at reviews for other Aneng products I have looked at, they perform very poorly against my tests. I have no interest spending the time to look at their other products.

[@terrybaileysr.3714]

Forgive me being a noob. I just ordered a nanovna-h4. It has not arrived yet. I ordered it so I could check SWR. So I thought I was supposed to hook it to my coax run to my antenna and get my SWR reading. So this is not what I do? I am confused. Every video I watched showed testing for SWR.

[@joesmith-je3tq]

Personally, I would use an SWR meter to measure SWR. Why are you wanting to use a VNA to make this measurement?

[@terrybaileysr.3714]

@@joesmith-je3tq Why? Because it is $70. I am not buying a $500 SWR to test a homemade dipole for a $100 radio.

[@joesmith-je3tq]

$500 for an SWR meter? Wow!

[@WaschyNumber1]

Nice video 👍🖖 I thought the nano is to Measure the swr of new antennas and the ohms ect and not for be burnt to hell 🤔 I'm totally new with the nano and ham radio, I'm in the process to make my license and learning all kind of stuff 😊 it's nice that people like you helping other people not to destroy ther equipment 😊

[@joesmith-je3tq]

Enjoy your new hobby.

[@reggindog3436]

As much as I like electronics it seems you could make this into something much more robust and turn the measurement into a more thoughtful process by just making a box with a NC pushbutton switch. Press the button and get your reading.

[@MakeDoAndMend1]

Ps Think about the millions of TV connected to aerials. They have protection built in. So it must be a bad design if susceptible to static etc. Cheers from old George

[@joesmith-je3tq]

Most of my higher BW equipment are not protected against ESD and have warnings on them. I would imagine if you forked over a quarter mill for a new Keysight, it will be similar. Of course, the people using equipment like this are normally well trained. Your simplistic comparison to a TV says a lot.

[@MakeDoAndMend1]

@@joesmith-je3tq Well said. Ps very few B/W tvs in the UK these days. 👍

[@bryanwheeler1608]

Most such devices have LC input circuits, where the inductor is at ground potential on one end. Others, still, use series capacitors to offer isolation from the Mains voltages in the case of breakdown of the isolation between Active & ground in the switchmode power supply, this will obviously protect the Tv from any DC potentials as well. Also, TV antennas often use feed methods which appear to DC as short circuits, hence preventing any charge buildup on the antenna. Many Amateur Radio beams, do the same, so the "charged up coax" problem is not universal, which just makes the exceptions where it occurs more insidious.

[@bertbronson8395]

That scenereo of 4kv on 1.5nF would yield about 5.3 mJ - even a cheapo tvs could handle that easily - but it wouldnt reach that with the tvs installed. Not sure how the tvs might affect the readings though. I am not sure whether the nanovna is capacitively coupled or not (seems to do dc so IDK) - but if it were it wouldnt bleed off a charge so perhaps that could damage it - but I would imagine it is dc coupled as far as 50 ohm is concerned. I am not very knowledgeable on rf or radio - but you have some good stuff in your video. I am trying to find tips like these so I dont blow my nanovna or tinysa out doing something stupid.

[@joesmith-je3tq]

Schematics for the original NanoVNA are available on-line. LiteVNA does have a clamp build into the unit. Of course, that's no match for the ham who transmits directly into their VNA with a 5kW PA. When it comes to preventing damage to test equipment, the most valuable tool you have is your head.

[@bertbronson8395]

@@joesmith-je3tq 5kW would be smokin LOL! Yea I worry about that stuff all the time. I really dont know much about vna's but at like $50 I couldnt resist. These things have like a 10mW input limit if I am not mistaken so I assume that limits you potentially to like 0.707v over 50 ohm I assume. Likely that is why I blew my Hameg HM5011 SA out with a fx generator many years ago SMH. So I am trying to see what the basic limits on these things are.

[@joesmith-je3tq]

Measure the output voltage then NEVER exceed that on the input.

[@SergeantExtreme]

I'm an absolute noob who isn't good at building electronic components. With that being said, what would you recommend as a something pre-built? For example, one thing I found while Google searching this issue is the Alpha Delta ATT3G50U. Would this do as good a job as the device you constructed? Thanks for any replies.

[@joesmith-je3tq]

IMO, just being aware of the potential to damage your test equipment with ESD and using some common practices to safeguard against it is the best thing you can do.

[@ernestb.2377]

Great stuff Joe. Recently I have bought a nanoVNA. It is still alive, but I will definitely try to build (or buy) something like this. Thank you very much for your time making the video. I have learned a bunch. Never thought over that the long coax could get charged. As is the VNA output low impedance, would it be detrimental for the SWR measurement to have a high ohm resistor in parallel? That would bleed the potential DC/static.

[@joesmith-je3tq]

Of course, had you watched the video and understood, you would know your statement on bad SWR is incorrect.

[@MakeDoAndMend1]

To me the answer is to incorporate in the design some protection circuit into the nano etc. Over many years using a working with test equipment. Multimeters such as Fluke. Beckman . Taylor and in the early days even Avo had a circuit breaker built into their bakelite analogue meters. Fluke uses pcb spark gaps and fast fuses. To stop or prevent damage from improper use. Tel line boxes have gas discharge tubes in the master socket in houses. Switch mode power suppliers have transient protectors as well as in rush current circuits. The list goes on . So to me its design is bad and for the price of adding protection is pennies. Especially with today's technology. Cheers from old George

[@joesmith-je3tq]

You are talking about equipment that works are very low frequencies. Protecting equipment that works into the microwaves and not compromise the signal integrity is not as simple as you suggest. Of course for the radio group connecting them directly to their amplifiers and charged up cables, they may not work about a couple hundred MHz. As I said in the video, it's all a trade off.

[@MakeDoAndMend1]

@@joesmith-je3tq Well as long as its clearly marked in the instructions booklet that under certain circumstances it could be damaged it shouldn't be such an issue. Cheers from old George. Ps my order for one hasn't arrived as yet. But they sent me a completely different product. No idea what it is. Video soon. 🤠👍🇬🇧

[@joesmith-je3tq]

Post a link once you have your video up. I'll have a look.

[@joesmith-je3tq]

@@MakeDoAndMend1 I saw your comment on the Tiny SA. From their site "WARNING!!!. The input signal must be below +10dBm otherwise the tinySA can be damaged. WARNING!!!. Using the supplied antenna makes the tinySA very susceptible for ESD damage or overloading. Only use the antenna with great caution. Never put the antenna close to a transmitter antenna " Of course the radio group can have 50' of coax charged up. Far from any HBM ESD event.

[@LawpickingLocksmith]

first part boring but rest made it up. Thanks Joe.

[@krzysztofsp8rak4]

What is this oscilloscope?

[@joesmith-je3tq]

There are no oscilloscopes in this video and I am sure you read the title.

[@krzysztofsp8rak4]

@@joesmith-je3tq 12:07 What is this?

[@joesmith-je3tq]

@@krzysztofsp8rak4 That is a old LeCroy 64Xi. There's a playlist off the main page with links to some of my other vintage LeCroy DSOs. I also own an old 8500A 7200 and 7200A.

[@krzysztofsp8rak4]

@@joesmith-je3tq Thanks for the answer ;)

[@skaramicke]

Surely it’s enough to _short_ the antenna to get rid of the static charge? Ground would not make a difference.

[@joesmith-je3tq]

Only you know what you mean by shorting the antenna and what you are calling ground. I could only guess. If you actually took the time to watch the video you are commenting on, what part did you find confusing?

[@greywolf271]

Case 1) Sure they were amateur radio operators or CB operators masquerading as Hams ?

[@joesmith-je3tq]

It's the internet and I am not there watching everyone. I have to assume they are telling the truth when they post. Here is a interesting video, starting at 9min in. Pay attention and read the comments: kzbin.info/www/bejne/qnSrcpRjqM-ambM I thought about getting a license again, but listened to it for some time and it was like CB was in the 70s.

[@kyoadam1593]

Hi joe can make a review on vc8145 80000 counts please.

[@joesmith-je3tq]

If you do a search on KZbin, you will find several reviews for this meter.

[@kyoadam1593]

Yes but not like yours sir please.

[@joesmith-je3tq]

@@kyoadam1593 I would not normally expect a bench meter to be as robust. I recently saved an old Fluke bench meter from the recycle that needs some work. It has some decent specs. If you're looking for a good bench meter, you may want to consider something used from one of the major brands.

[@kyoadam1593]

Vc8145 is garbage i know but the resolution is nice, the meter need a modification and you are the only one that i know sir you can do it .am not gonna push it more than that.

[@joesmith-je3tq]

@@kyoadam1593 I do not normally publish details on the handheld meters I modify so I doubt you would gain anything there. 80K count is decent resolution for a handheld but not so much for a bench meter. I would expect the accuracy will also be higher for the name brand meters. Just depends what you need.

[@standegroff3270]

Does any one have the unit for sale for HF Thru 2 meters??? Nice job. I'd buy it now !

[@joesmith-je3tq]

Maybe but as long as you follow good practices, you will be fine.

[@2321brendan]

I assume the noobs who blow up their nanos are connecting them as they would an SWR meter. These often have power ratings to several hundred watts. If they purchased the nano mainly to measure the antenna-feedline SWR ,then assuming the device works the same could be an easy mistake to make.

[@joesmith-je3tq]

I wouldn't have considered that but it wouldn't surprise me in the least based on my interactions with some of them.

[@northerncanuck]

I think this is the issue right here. My radio club is going crazy over these things because they are inexpensive, but this disclaimer is not being made. It's only being advertised as an inexpensive SWR meter (though in the course itself it's stressed our antennas and systems need to be properly grounded). I'm glad I'm reading into these potential issues ahead of time.

[@danieljohnson8437]

Excellent

[@ralvarezb78]

wtfr ? nanovna is generating square wave ??

[@joesmith-je3tq]

Please watch the following: kzbin.info/www/bejne/r2fMgId7ipuNsNE

[@ЭлБанди-ж4ц]

hello, your videos are interesting, please include subtitles.

[@TonyLing]

Very smart. Thanks.

[@messageobliquespe100]

Hey Joe - where you going with that gun in your hand (Hendrix). Thoroughly enjoy your Vids / knowledge & firing the loaded revolver to some of the comments. I shall remove electrostatic build up by the tongue method on all devices before connecting. Thanks 👍

[@Jibs-HappyDesigns-990]

🐕🧐👉👍👈🦞 correct me if I'm wrong? U can make a reverse polarity circuit, or an over voltage circuit. not a lightning protection plug.... because of the operating frequencies, and the communication line probably needs 2 stay simple? with a ''new'' nano vna.. I have setup a 4watt fuse, for cellular communications testing! and I have also made a ?120 - 75 Ohm antenna 4 way/& 2 way resistor bridge...i.e. antenna balun...I also use, the nano vna pcb test board!! ok, maybe I'm sounding, all over the place.....some ''cellular'' boosters have over voltage circuits, and reverse polarity circuit's I could re-design...I would like 2 make a video..eh??some day?? if I know enough about this?? 4 all I know, I sound like I'm selling hamsters. 2 a steak house?

[@ebaystars]

you should manufacture and market at happy-ham prices a lot the PCBs you make as a lot of users have no time to build such stuff or the patience or skill OR eyesight! Call yourself the VNA Guru :-) thanks for the tips I am migrating from my 8753A which the ex wife threw in the dumpster (grrrrrr) to Nano/Tiny SAs in thailand 🙂

[@joesmith-je3tq]

I am surprised by that fact your wife could pick up your 8753A to throw it. The video makes it clear that how you protect a device like this will depend on a lot of variables. The goal was to educate, not to make any sales. A cheap VSWR meter may be a better choice. Certainly more robust.

[@ebaystars]

@@joesmith-je3tq it was her new husband and my daughter who doesnt like me any more that did it and the S-parameter test set as well also a lot of ex mil equipment, they then decided to selll stuff on fleabay = glitchfunk, proper-radios, lushmush007 etc, lownoisefloor sad but true

[@VK3EGN1]

Using GDT to limit voltage to 500 V would allow 10A current into VNA. Even using GDT with 50V limit is very bad idea. TL transformer 1:1 is much better option.

[@joesmith-je3tq]

What are you going on about?

[@VK3EGN1]

@@joesmith-je3tq you can't understand?

[@joesmith-je3tq]

@@VK3EGN1 No

[@joesmith-je3tq]

I would imagine in a simplistic view, say not watching the video and just wanting to comment, you may suggest that 500V/50ohm gets you your 10A. Of course once it fires, its a short but until that time... However, the GDT will be VERY slow and the peak currents will be MUCH higher. It really depends on the wave shape. Still, that's not what is being shown in the video. Had you taken the time to watch it, there was a sacrificial attenuator and TVS that are after the GDT. The TVS will switch very fast and can easily handle fast slew rates like we see with ESD events. A VNA is a wide band device. Using a transformer would really hurt the performance not to mention that fast transients are still going to blow through it. Capacitance of the windings and such... The clamp I show would still hurt the VNAs performance but I went over that. I suspect you just didn't watch the video.

[@VK3EGN1]

@@joesmith-je3tq you are right. Few early mistakes you made put me off , and I did not watch the entire video. It does get better later. For lightning protection I use both GDT and TVS. The best protection is transformer you hate so much. I use end fed antennas 120 m tall (400 feet). There is always at least 12kV potential difference between top and bottom of the antenna. Simple auto-transformer is excellent static drain, it shorts all static charge to ground. I use at least 3 baluns, with earth stake after each. Why use diodes as input protection for Spectrum Analyzer or receiver ? Dynamic range would be severely limited, say 75 dB or less. Would you use one wideband transmission line transformer for all frequencies under the sun ? I would not, there are many different magnetic materials. Anything we make can only be good over some frequency range.

[@edmccomb4624]

Good video

[@w5cdt]

You must work in the semiconductor business. ;-)

[@jamesgeorge1709]

So what to hell do you do.

[@joesmith-je3tq]

Wake up, SSS, dress, have a cup of coffee....

[@ernieschatz3783]

Polyphasers

[@josephkaminski1857]

this was all totally unnecessary and alters the resonant freq of the DUT. (1) first of all, No matter what amount of capacitance is in the line and antenna that the NANO is measuring, it can only charge that line capacitance to a level of the Nano output signal RMS value. that voltage is accounted for in the nano design of signal output and line returns paths. (2) the DUT resonant freq is altered by this effective tank/DC bleed circuit you have and makes the NANO RLC time constant measurements wrong. The only thing anyone really needs to be concerned with is discharging the DUT before then begin testing. After that the max RMS value that the DUT can possibly have is from the nano own RMS output levels , which is more than accounted for in the NANO design. The real way People blow up nanos is When they do signal injection to the DUT from a signal generator, while using the nano to make measurements. They tend to drive the line with too much signal power. I don't understand why they do that because it is not needed with a NANO to make measurements.

[@joesmith-je3tq]

Consider joining the EEVBLOG and posting your concerns there. I have a running thread for the NanoVNA. Feel free to use that or start a new one. www.eevblog.com/forum/rf-microwave/nanovna-custom-software/ YT isn't really a good platform for having a discussion. That said, when you talk about my "tank" circuit, keep in mind that in the the context of this video we are using a VNA which is limited to 300MHz. While I did demonstrate the effects the clamp had on the measurement, maybe I missed something. As for discharging the DUT, that was all covered in the first few minutes of the video.

[@joesmith-je3tq]

I have included your comment to another thread I had started for this clamp. www.eevblog.com/forum/rf-microwave/nanovna-input-protection/msg5188131/#msg5188131

[@wb7wbw-l2p]

I have a headache!

[@CR-wk4qt]

Sooo why aren't you creating a protection product that we can buy? You'd be rich

[@joesmith-je3tq]

I explained how many variables there are and why there isn't a one size fits all. If someone offered such a device promising it would protect their VNA from all possible conditions and still allow the VNA to make any sort of useful measurement, a ham would connect their VNA directly to their PA or their 1000' of coax charged to 4kV and call foul. It's better to explain the hows and whys and let users design their own protection.

[@ToNzHoLtZ]

Dumb question, can I use any 50Ω load on my nano vna ? And does the vna sweep DTF?

[@joesmith-je3tq]

The dumb answer is, you can measure any 50 ohm resistor on your NanoVNA and you can use any 50 ohm resistor for a standard. Lets assume DTF is TDR and be sweep, you just want to know if the VNA has this feature. Because I don't use these VNAs standalone (they are always connected to a PC where I use my own software) and with the firmware in my NanoVNA being several years old, I really don't know.