NanoVNA V2 aka S-A-A-2

[ogden]

To measure PCB trace impedance, better make through fixture for S21 measurements like shown here. Your S11 results show impossible - line impedance wandering between 25 and 200 Ohms. Do you know why?

[Mechatrommer]

To measure PCB trace impedance, better make through fixture for S21 measurements like shown here.

that is to test components like capacitors (shunted to ground), not PCB trace tester, how to shunt a pcb (DUT) on that tester pcb? anyway my KC901V doesnt support S21 impedance analyzer, i'm not sure if NanoVNA has. i also have "through" PCB included in my VNA Test Plane setup above if i want to do such thing. its compatible for both SMA and BNC connectors. i have few like 10 or 20 pcs from previous orders.

Your S11 results show impossible - line impedance wandering between 25 and 200 Ohms. Do you know why?

its a combination of line and termination impedance. they are all parasitics and strays that resulted varying impedance across frequencies. reflection due to 50 ohm mismatch is one of the thing.

[ogden]

that is to test components like capacitors (shunted to ground), not PCB trace tester, how to shunt a pcb (DUT) on that tester pcb?

Just don't. For verification of transmission line design and PCB materials/process you do not need to measure same exact trace. Measure another thru trace of same design on same panel, made specially for purpose of impedance control - as most RF engineers do. Sometimes they put impedance control strip on tooling frame of the panel. Of course when you want to measure capacitor on the fixture - then you need SOL kit you made out of same fixture.

[Mechatrommer]

Measure another thru trace of same design on same panel, made specially for purpose of impedance control - as most RF engineers do.

RF engineers use another type of VNA for verification, not like NanoVNA nor KC901V... ie full 2 port VNA.. thats why their e-cal is connected to both VNA ports during CAL (there is switching inside e-cal). NanoVNA, Deepace and any other cheap VNA only require CAL on port 1 (ch0), port 2 (ch1) cant be CAL'ed the same way as full 2 port VNA. they the RF engineers have different workflow. afaik there is no way to measure trace impedance using S21 method (only can measure gain/loss and phase/delay), without terminating it properly and probing reflection from it. on cheap VNA, only S11 can do that afaik. or do you have any reference that state specifically exactly this? (measuring trace impedance from S21) or at least can you demonstrate how to do that on NanoVNA?

[ogden]

Yes you are right. No S21. I just have been told that one end of 2-port test strip you attacht VNA, but another - to 50 Ohm cal standard. Silly me thinking that 2 terminals means S21 Usually looking at S11 Smith chart and return loss is enough.

[TimFox]

Can one connect two NanoVNAs together to obtain a full two-port VNA?

[ogden]

Can one connect two NanoVNAs together to obtain a full two-port VNA?

It could be possible to somehow frankenstein two NanoVNA's together, but it is not worth it. You won't get functional 2-port VNA anyway. Better just swap cables to measure your DUT other way around. Hint: for S11 use external terminator instead of Port2.

[Mechatrommer]

Can one connect two NanoVNAs together to obtain a full two-port VNA?

the units need to be in synched, otherwise i dont see it how. while conversing with odgen, i found a diy full 2 port 6GHz VNA site from 2 years ago... http://www.yl3akb.lv/content/vna_v2/vna_v2.php i'm not sure why the guy didnt pursue it (no update) its promising. with OwO roadmap of not-full 2 port 6GHz is ahead, i guess full 2 port version will take another years. but... we learnt to deal on how to get S12 and S22, just turn the DUT over, ie its output that once connected to P2 is now connected to P1 vice versa. the more we dig into this, the more we realize there a lot more "s-parameters goodies" we are missing, such as the S21 impedance analyzer, and transmission line Zc plotter (see below)...

Yes you are right. No S21. I just have been told that one end of 2-port test strip you attacht VNA, but another - to 50 Ohm cal standard...

i figured this method while i started to collect few "better" quality coax cable such as Huber Suhner, Gore and China semi rigid coax. starting from here Performance of China 50 ohm Coaxial Cable it maybe not so obvious how i did it, or maybe you all know it already. i was happy go lucky using some hunglow coax cable that later i figured out as crappy (wobbling as you can see in my plots above) it is usefull though if operating frequency is carefully selected when crossing the desired impedance. i didnt find on how to test coax or stripline's Zc in definitive and easy way without extensive math matrix. so i have to find my own "subjective" way (good coax or stripline will have flatter plot close to its Zc when terminated with its Zc (characteristic impedance)) but searching again, i found the method, but still it requires math in this post by Bud...

https://www.eevblog.com/forum/rf-microwave/vna-measurements-of-pcb-transmission-line/msg1775117/#msg1775117
https://chemandy.com/technical-articles/measuring-track-characteristic-impedance/measuring-track-characteristic-impedance-article1.htm

it will be nice if a VNA can implement this "goody" (automated) into their FW/GUI or PC SW. but what can we expect from a cheap tool? designers with limited resources? sometime i think i want to diy VNA that fullfill many requirements, but its going to waste a lot of my time designing, respinning prototype pcbs, buying parts (wrong parts) and understanding the heavy math, so i'd rather doing fun stuffs (my area of interest) than building another T&M tool, actually i'm currently building another T&M tools, on and off its been years of prototyping and verifying, so obviously there is no empty slot for another tool atm. OwO and the team are so close at this but maybe they are too busy with other stuffs and "directive". the yl3akb/VentRF guy had a longer vision ahead with his full 2 port 6GHz VNA.

i think we wandered off topic already, where was i? Reply #315 VNA View is nice we can key in CAL kit's characteristic s1p files, if i know how to use this correctly and if the feature is working correctly at all, i should be able to trace back NanoVNA cal kit (with respect) to my Kirkby CAl kit by creating their s1p files and then back to HP/Agilent CAL kit thats Mr Kirkby was using when tracing/characterizing mine... hopefully.. but always there are time needed to do the learning.

[ogden]

i found a diy full 2 port 6GHz VNA site from 2 years ago... http://www.yl3akb.lv/content/vna_v2/vna_v2.php i'm not sure why the guy didnt pursue it (no update) its promising.

Yes, very promising project. When you sum it all up - you will see that BOM alone exceeds pain treshold of DIY and enthusiast buyers, approaching level of commercial low end tools. Cost is always cooling factor for project/idea to become insanely popular (speculation).

[thinkfat]

I'm trying to rebuild the firmware for the v2plus4 from the git repository, but I'm getting a non-working binary out of it. Basically I followed the README, installed the latest ARM toolchain and tried recompiling the "master" branch. Firmware is built, but after DFU upload, I just get a blank white screen.

Tried recompiling the 20201013 release (git checkout 20201013) but didn't work, I get a missing include file (nvic.h) from inside mculib.

Any pointers?

PS: got it to work. There was a hiccup with the linker file, something modified and broke it. Once I restored it to the state in git, the build worked fine.

[innkeeper]

what is the maximum input dbm on the v2.2 board?

[hpmaxim]

Looks like the 4" is back in stock.

Before I pull the trigger on this, is there anything I should know?  Is a new rev due out soon? Are there known hardware issues (less concerned about software if it will get fixed and I can update the firmware) which I should wait on getting resolved before I buy, etc?

[joeqsmith]

Looks like the 4" is back in stock.

Before I pull the trigger on this, is there anything I should know?  Is a new rev due out soon? Are there known hardware issues (less concerned about software if it will get fixed and I can update the firmware) which I should wait on getting resolved before I buy, etc?

https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg3329742/#msg3329742

[joeqsmith]

what is the maximum input dbm on the v2.2 board?

Maximum where it first starts to go nonlinear?  Maximum as in the 3dB compression point?  Maximum where smoke rolls out of it?  Maximum where nothing is left but chard electronics?   

Keep it below what the output signal is and you should be fine. 

[KD0CAC John]

Yes , got the email this morning and ordered .
Have to checkout your update

[hpmaxim]

Looks like the 4" is back in stock.

Before I pull the trigger on this, is there anything I should know?  Is a new rev due out soon? Are there known hardware issues (less concerned about software if it will get fixed and I can update the firmware) which I should wait on getting resolved before I buy, etc?

https://www.eevblog.com/forum/rf-microwave/nanovna-custom-software/msg3329742/#msg3329742

Some sort of birdie at 3.7GHz perhaps?  Honestly, above 1.5GHz, I can't think of anything I'd really care about until 2.4GHz, and then I can't imagine what I would care about until 5GHz.  How is performance below 3GHz?

[joeqsmith]

Go back a few posts in that thread and start reading.  I've provided a fair amount of information if you're interested. 

[hpmaxim]

Looks like your basic conclusion was NanoVNA (original) is just fine if you are below 1GHZ and VNA2+  is okay from 1 to 3 GHz... Above 3 GHz it's like playing horseshoes with a blind person?

I have (or rather had since it seems to have disappeared into the abyss along with half a dozen other things) an original.

[joeqsmith]

I typically suggest staying below 300MHz with the original Nano.   The V2+ and +4 run fine, sort of below a GHz.  The inability to look at narrow band filters IMO was a big miss but I experiment a fair amount.  If all you are doing is trying to measure your antenna SWR, this really doesn't matter.   

I was really surprised to see the poor performance above 3GHz with the V2+4.  I was even more surprised when I looked at the MidWest attenuators with the V2+/+4 and the v2p was more stable.   The fact they advertise the   V2+4 for 4GHZ and the V2+ for 3GHz, makes no sense to me.   They are both poor above 3GHz.   

These low cost units IMO, make a really good training tool.  If you want to play with sub 300MHz circuits and are trying for example to make your own SSB radios, the original Nano may be a better choice.   If you want to play with microwave designs, the V2+4 is really the better choice.   If you were tuning wide band filters for example and wanted a faster update rate (so you can see the effects of your adjustments live) the V2+4 is a big improvement over the original Nano.  If you were playing with very low noise circuits, like that 50dB attenuator we were making in another thread.  That was really pushing the original Nano.  The V2+4 would again be a better choice. 

Of course if you look at the data I have shown, there's a bit of difference these low cost units and my vintage boat anchors but if you are just trying to learn, I don't think the shortcomings of these units a that big of a deal.   IMO, they are the perfect beginners tool and can throw up some pretty decent data depending what you use them for.   I had made up some simple microwave experiments that I thought may have been fun for beginners to try and build at home and learn more about it.   

If you have some specific test you would like to see ran, feel free to ask.  It's possible I may be able to set it up for you.   

[cdev]

The missing piece of the puzzle for antenna experimenters is some means of automating the antenna pattern testing process, (assuming you have access to some open space, an RF anechoic chamber is likely out of reach for most of us)

I think the easiest way to do that would be using stepper motors and perhaps a nice A/B relay setup, kind of like what optometrists who use the old fashioned setups do for picking what lenses to use in glasses.

I think its possible to use relays to extend the functionality of a two port VNA to make an effective four port VNA too. (Or so I read in QEX a while ago)

Joe, the same relays are used as the tiny low voltage Omron ones you use in your switch box.

[hpmaxim]

I have to confess, my immediate need is checking an aviation (118-136MHz) antenna.  I love having toys, and being able to say: "Hey, I've got a 2 port 4 GHz VNA!" is good bragging rights (without mentioning its $30/60/120).  But I don't routinely build RF circuits, and other than perhaps characterizing components for self-resonant frequency, I'm not sure what I'd do with it.

[joeqsmith]

I have to confess, my immediate need is checking an aviation (118-136MHz) antenna.  I love having toys, and being able to say: "Hey, I've got a 2 port 4 GHz VNA!" is good bragging rights (without mentioning its $30/60/120).  But I don't routinely build RF circuits, and other than perhaps characterizing components for self-resonant frequency, I'm not sure what I'd do with it.

 

I think the thing to do is just stay in the forums and claim you are a EE with 40 years of RF design experience and claim you personally own, say a mill in new TE.   That's the cheapest way out.

The Nano has a single receiver and can't measure all four S-parameters.  You really need something better.   That and the Nano is so cheap, all your friends will already have one.  Your goal should be to one up them!   

I saved some pictures of people who have set up some really nice non-functioning labs for show.  That may be another option.  Buy everything damaged and set it all up so it looks nice.  Maybe have a cheap scope you can turn on if people come over.  Maybe get some cheap unfinished projects on eBay to place on the bench to make it look more real.   Costs a little more but for some real bragging rights, seems effective.   

I would say, forget the bragging rights, find that original Nano and learn how to use it.   If you are working below 300MHz, it can throw up some very impressive data.  If you want to brag, brag about how much you have learned from using the Nano. 

[joeqsmith]

...

I think its possible to use relays to extend the functionality of a two port VNA to make an effective four port VNA too. (Or so I read in QEX a while ago)

Joe, the same relays are used as the tiny low voltage Omron ones you use in your switch box.

I think those were $10-$20 each.  They work alright but the isolation was poor.   I have an old Transco relay that I made up a really crappy DC-DC to drive it from the USB port.  My software supports it.  I plan to mount that along with a couple of bias-t's and maybe a decent step attenuator.   But then I think, I should really add some mixers and some better couplers and maybe a wide band amp......       Reality always steps in. 

[hpmaxim]

I have to confess, my immediate need is checking an aviation (118-136MHz) antenna.  I love having toys, and being able to say: "Hey, I've got a 2 port 4 GHz VNA!" is good bragging rights (without mentioning its $30/60/120).  But I don't routinely build RF circuits, and other than perhaps characterizing components for self-resonant frequency, I'm not sure what I'd do with it.

 

I think the thing to do is just stay in the forums and claim you are a EE with 40 years of RF design experience and claim you personally own, say a mill in new TE.   That's the cheapest way out.

The Nano has a single receiver and can't measure all four S-parameters.  You really need something better.   That and the Nano is so cheap, all your friends will already have one.  Your goal should be to one up them!   

I saved some pictures of people who have set up some really nice non-functioning labs for show.  That may be another option.  Buy everything damaged and set it all up so it looks nice.  Maybe have a cheap scope you can turn on if people come over.  Maybe get some cheap unfinished projects on eBay to place on the bench to make it look more real.   Costs a little more but for some real bragging rights, seems effective.   

I would say, forget the bragging rights, find that original Nano and learn how to use it.   If you are working below 300MHz, it can throw up some very impressive data.  If you want to brag, brag about how much you have learned from using the Nano.

I'm an EE with 20+ years of IC design experience.  Also an Extra Class ham who hasn't touched a ham radio in a decade, maybe longer...  but fairly limited RF experience.

[mawyatt]

I have to confess, my immediate need is checking an aviation (118-136MHz) antenna.  I love having toys, and being able to say: "Hey, I've got a 2 port 4 GHz VNA!" is good bragging rights (without mentioning its $30/60/120).  But I don't routinely build RF circuits, and other than perhaps characterizing components for self-resonant frequency, I'm not sure what I'd do with it.

 

I think the thing to do is just stay in the forums and claim you are a EE with 40 years of RF design experience and claim you personally own, say a mill in new TE.   That's the cheapest way out.

The Nano has a single receiver and can't measure all four S-parameters.  You really need something better.   That and the Nano is so cheap, all your friends will already have one.  Your goal should be to one up them!   

I saved some pictures of people who have set up some really nice non-functioning labs for show.  That may be another option.  Buy everything damaged and set it all up so it looks nice.  Maybe have a cheap scope you can turn on if people come over.  Maybe get some cheap unfinished projects on eBay to place on the bench to make it look more real.   Costs a little more but for some real bragging rights, seems effective.   

I would say, forget the bragging rights, find that original Nano and learn how to use it.   If you are working below 300MHz, it can throw up some very impressive data.  If you want to brag, brag about how much you have learned from using the Nano.

I'm an EE with 20+ years of IC design experience.  Also an Extra Class ham who hasn't touched a ham radio in a decade, maybe longer...  but fairly limited RF experience.

Without the spectacular ICs that folks have designed, there wouldn't be any NanoVNAs, TinySAs, moderately priced DSOs, AWGs, or SAs for that matter. We'd be tossed back into the days when a scope, or even signal generator, outside of a Heathkit or B&K, weren't priced within reach of a hobbyist. We wouldn't have the Smartphones, computers, laptops or reasonable internet access either

So Hat's off to the IC designers that have and are continuing to create the future

Best,