nano vna

[radiolistener]

turns out its from china!,seller hasnt replied to my mails so trying to get my money back via ebay,seems a lot of recomendations are bogus!!

original NanoVNA-H is from China. If you bought it from other source you're at risk. There are also a lot of clones of NanoVNA. Some of them may have bad perofomance and some may be defective.

In order to protect your money I recommend to buy on aliexpress. If you won't receive item or get defective item, you can open dispute and return your money. It works safe for buyer.

[m3vuv]

I spoke too soon,it was delivered about 15 mins after my post!,seems ok except the thunbwheel thing its total garbage,that seems normal tho i take it now just need the windows s/w for it the nanovna saver ver 0. 2.0 exe is crap,the screen image jitters all over the place and is unusable,anyone know of a decent one?,the vna has 0.2.3-2-g8ac9166 firmware,my pc is running win7 64 bit sp1,cheers.

[bd139]

Yeah I don’t use the thumb wheel on mine. You can poke the display with a bic lid where you want to dump the cursor.

[radiolistener]

seems ok except the thunbwheel thing its total garbage

yeah, my NanoVNA also has terrible thumbwheel. It has false triggering.

[m3vuv]

my thumbwheel flexes big time,i m going to superglue a support ie spacer/shim from the top board to the center of the thumbwheel,should cure it!

[bob91343]

I just use an old drafting pencil made of metal.  The 'wrong' end is a perfect stylus and I can do anything I want.

I have said it before but will repeat that the nano is fantastic.  It does it all, and so cheap and portable.  I have stocked up on SMA cables and adapters so now I can do anything.  I do anticipate failure of the connectors but new ones are easy to install.  Power switches are very cheap, like only a few cents each.  This is finally something done right, and I love mine (obviously).

I don't connect mine to the computer although I did try that for a while.  Sometimes the small display is a bit hard to read but I keep a magnifier handy.  I would guess that in direct sunlight it wouldn't be very good.

It measures L, C, and R, and propagation delay and characteristic impedance and SWR and line length and coax attenuation.  I got my money's worth in the first hour and it keeps surprising me.  And there are some menu options I haven't tried yet.

[m3vuv]

is there any advantage of upgrading the firmware on these ?

[bd139]

I have a personal approach that if it’s an embedded system and not network connected then don’t touch it if it works. Has done me well over the years

[erikka]

Depends on what firmware you have now.
Here you can find a comparison table
https://groups.io/g/nanovna-users/message/7477

[m3vuv]

my firmware version is: 0.2.3-2-g8ac9166
i cant find it on the chart/list.

[m3vuv]

Well,ive been trying to load the hugens firmware on to the vna,it only has 2 traces but bigger fonts,supposedly!,i downloaded DfUse demo and instaled the drivers etc,loaded the  DMR_clear memory file then tried to install the new firmware with the nano in dfu mode,it all went ok,said file uploaded ok,now the big but,when i poer the vna on,i get the same f/w version number displayed,it looks exactly as if nothing has changed,even my old cal data is there,it says uploaded ok but obviously hasnt uploaded a thin,any ideas?,73 m3vuv.

[xrunner]

m3vuv, I don't know what the problem is, might try a different version of firmware from another source. 


Great new manual for the NanoVNA from Prof. Gunthard Kraus, go to the link and then the content. You can download the PDF file.

Tutorial in three parts (Version 1.4.2. / December 2019) for the NanoVNA Vector Network Analyzer

[bd139]

This is why I didn't futz with mine 

[xrunner]

This is why I didn't futz with mine 

You don't like mini-bricks? 

[radiolistener]

You don't like mini-bricks? 

there is no way to brick NanoVNA. You can always reflash it.

[xrunner]

You don't like mini-bricks? 

there is no way to brick NanoVNA. You can always reflash it.

I know that ... it's a joke.

[bd139]

I could brick it!

Too busy using mine to play with firmware! So this lunch time I built a small HF amplifier based on W7ZOI's termination insensitive amplifier notes to go in the middle of a receiver I am building. Target 15dB across 80,40,20m bands. I think we have a winner. Pretty flat gain across HF (not bad for 2n3904's):



Good return loss:

[radiolistener]

bd139, it's dangerous to put amplifier output directly to CH1.
NanoVNA input expects -10 dBm level.
In your case it's about +5...+10 dBm. This is too high.

I recommend to put attenuator equals or higher than amplifier gain on the output and about 20 dB on the input.

After such experiment, I would check if the СH1 port is still working properly. There is a high risk to burn it 

[bd139]

Yeah there's 20dB in there

Edit: This is a small signal amplifier so it's on the input. If it was a large signal I'd put my 200W 40dB power tap on the input

Edit 2: also I need to test RL of input properly still. I'm testing the 20dB attenuator there 

[xrunner]

He's attenuating the input to the amp to test it's gain.

[radiolistener]

Looks very much to me like he's got an attenuator in line...

he put attenuator on the amplifier input, but amplifier output connected directly to the NanoVNA.

NanoVNA full scale is about -10 dBm, which is displayed as 0 dB on the S21 graph.
As you can see there is +15 dB on his S21 graph.
It means that there is at least +5 dBm level on CH1 input. This is too high.

But we cannot be sure that the level is not higher that +5 dBm because input level is close to overload level. So, it's very possible, that input is overloaded and we see just a max possible value with a curve due to calibration.

So, there is possible much higher power on the input. This is why I suggested to check if CH1 still works ok...

I suggest to never exceed 0 dBm level on the NanoVNA input.
And for more reliable measurements it's better to not exceed -10 dBm.

[bd139]

Doubt it's a problem otherwise it'd blow up when you did the through calibration.

OUTpwr + -20dB + 16dB = INpwr

Therefore INpwr < OUTpwr is always true.

Edit: for reference, the 20dB attenuator is calibrated out above. Perhaps that's where it is confusing?

[radiolistener]

Edit 2: also I need to test RL of input properly still. I'm testing the 20dB attenuator there 

in order to do that you can calibrate NanoVNA through 20 dB attenuator. The dynamic range will be 20 dB less of course.

Another way is to attach dummy load on the amplifier output and connect CH0 directly to amplifier input. But it may saturate amplifier. NanoVNA ouput is -10 dBm, so you're needs to check if your amplifier can handle such input power with no saturation.

[bd139]

Input can handle that fine. There is major gain compression though according to LTspice. I'll run it and see what happens.

[radiolistener]

Edit: for reference, the 20dB attenuator is calibrated out above. Perhaps that's where it is confusing?

+5-20 = -15 dBm, that's looks good.

But I never connect amplifier directly to NanoVNA input, even if it's gain is not high.
Attenuator also add protection from short transient pulses.