How not to damage your NanoVNA when measuring SWR 

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

me too, thank you

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

Thanks and enjoy your stay.

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

I suggest the Lex NanoVNA ESD Saver.

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.

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.

@@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.

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.

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.

Take the time to read the description.

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. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-XaYBpPCo1qk.html Of course, if you can't work with a squarewave drive, you will need to open your wallet. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-y6iOTEU6Zzo.html

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

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

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.

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.

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 !!!

@@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?

​@@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.

@@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?

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.

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

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

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

Enjoy your new hobby.

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.

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. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-JHsgbu7brYI.html

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.

@@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.

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.

​@@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 :)

@@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.

@@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.

@@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: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-tCHAa-sjgcQ.html I think the best protection starts with education.

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.

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.

@@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.

@@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....

@@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.

@@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.

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.

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.

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

@@WogChilli Resistors can certainly have a low impedance.

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.

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

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.

@@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.

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

You would need to ask them. Here is a video where a ham is teaching other hams the proper way to use a VNA. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-tCHAa-sjgcQ.html

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

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

$500 for an SWR meter? Wow!

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?

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: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-tCHAa-sjgcQ.html I thought about getting a license again, but listened to it for some time and it was like CB was in the 70s.

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

If you do a search on RU-vid, you will find several reviews for this meter.

Yes but not like yours sir please.

@@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.

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.

@@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.

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.

@@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. 🤠👍🇬🇧

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

@@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.

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

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.

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.

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

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.

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

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

@@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.

@@joesmith-je3tq Thanks for the answer ;)

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.

@@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

Please watch the following: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-y6iOTEU6Zzo.html

What are you going on about?

@@joesmith-je3tq you can't understand?

@@VK3EGN1 No

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.

@@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.

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

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.

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.

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

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.