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There are three active devs right now.
edy555 is the originator of the Nanovna,
hugen created the 2.8" version that everyone is familiar with
DiSlord fixed many bugs and re-wrote sections of the firmware and added additional functions
All 3 are on github.? Refer to the forum wiki and look at the user guide I edit (forum files section) for info on firmware.
Since you seem to not trust anything from the internet,? just leave your unit as is and use it with the older firmware, which is still capable enough but doesn't have the many improvements of current firmware.
Read the forum posts as well and go through the forum Wiki. It will answer most of your questions.
...Larry

Hi Larry,

Ok on the firmware. I thought it should be reasonable as its only Feb this year, but then there are variants of firmware from more than one developer, mine is labelled @edy555.

Forgive me but 'handles' such as that (and I don't know the person in question at all) also convey a 'dark web' feel about them. That said, I have gathered that said person DiSlord is a key contributor to NanoVNA firmware, but as stated it is highly confusing when there are apparently 'alternate' developer firmware releases. Which can or should you trust getting it from GitHub. I have no idea.

Suffice to say I struggle to trust downloads from the internet which combined with many posts I've also read debating compatibility of variants of the actual Nano hardware, that also put up huge warning signs as I have not idea how safe and compatible these things are. What I have works, it isn't the most intuitive of devices but it does seem to work.

I suppose the question is can I get the data I am looking for from my device as is?

Kind regards
Phil

Thanks Bert,

Up to 1 GHz should be enough for my needs.

Best regards
Nick

Thanks Steve.
Really appreciate your comments. I now just need to get parts together and give it a go.

Best regards
Nick

It's here:

With regard to stability. After you build a test set and ready to take it to your little vna to test... DO NOT!!!

Always initially test your DUT system first with 50 terminations on a spectrum analyzer and carefully look for oscillations. Yes, pad the SA and slowly remove pad to gain some dynamic range while searching for any oscillation.

If you skip this step and you apply your unstable DUT to the vna and it does oscillate you run the risk of taking out the channel 0 or ch 1 front end.

I have seen this occur on many vna's in the past and the price you pay is painful!!

Also see note 77-1 hp transistor parameter measurements. The fixtures presented are excellent for the time and a review of the grand daddy of vna test sets is discussed, the vector voltmeter. A must read. Let me know if you cannot find.

Alan

Hello,

I only have experience measuring S parameters of LDMOS devices in the 1-500
Mhz range;

What is critical is to feed the transistor with a DC good choke system
(drain) and a good Bias system (Gate) which performs well in the frequency
range that you are measuring. Establishing that the DC Choke and bias
system perform well in the frequency range of interest is therefore an
extremely important pre-requisiste before doing any measurements. For
instance there is no point trying to measure an LDMOS in the 800-900 Mhz
range if the types of Chokes used on the drain stop being effective above
300 Mhz due to stray capacitance of the Choke.

Then there is the stability issue. Some transistors, especially old
generation ones with a relatively high drain-gate capacitor of 10-20 pf
(ie, miller capacitor) will tend to oscillate more easily spontaneously
(often resonating with the DC choke if is too high Q) than the modern ones
where the drain-gate capacitor is reduced to 1 or 2 pf only. Practically
this means that to be measurable, the transistor may need to be stabilized
with a combination of the following (a) shunt resistor between gate and
ground (b) serial resistor between gate and the source generator (c)
feedback resistor between gate and drain. Of course these stabilisation
resistors, when present, affect the measurement of the S parameters....so
what is measured is not the parameter of the transistor but of the fixture
plus transistor. . Ideally it should be possible to deembed the effect of
those stabilizing resistors but I have not found any tools that allow to do
that easily. So, what I do instead , when a transistor requires to be
stabilised to be measured, is to make a range of measurements with
different combination of stabilizing resistors (so I get a complete
picture).

Thanks
Regards
Peter

Hi Phil,
That version of FW is quite old so you may want to update to the latest version 1.0.38 to get newer features and bug fixes.
Scroll back in the forum and search for messages from DiSlord with attachments and you'll find his latest DFU file.
Welcome to the forum!
...Larry

Hi I am a new user for the NanoVNA H4 The Firmware is version 0.5.0 built Feb 21 2020 - 12:55:37.

I bought it along with the RF Demo board to try and learn a bit more about using it, which hasn't been easy as there is no documentation on the settings to obtain the outputs presented on the demo board. That has made it a game of investigation to change calibration ranges to obtain results that resemble the expected output. Result is, not a lot of learning coming from this.

The next thing is I am using it to test an antenna that I am making and whenever I read articles they are discussing the parameters shown in the title of this posting.

Scanning an S11 vswr plot is ok but where to fine the other paranmeters of Z, R, X and L is a complete mystery. Certainly there is no table of these figures that I can find, SO is there a way that I can find these measurements that somebody can help me with?

Thank you
Phil G0KDT.

Well, I am not an expert, but calibrating with a mmx standard where you suggest should work. It will eliminate all the transmission blips going through all the connectors. It probably is not feasable to try calibrating right up at the aerial as you do not want to disconnect the inbuilt lead from the aerial. The effect of that last bit of coax will heavily depend on how good it is.

But unless your time is severely limited, try calibrating further back as well. After all this is how you learn.

Some time ago there was a fad of making directional wifi aerials (2.3ghz) from Pringle tubes and tin cans etc. You followed the instructions. Now, with the nanovna it would be a walk in the park. Why not try to make a larger version of those?

Steve L G7PSZ

Thanks Steve for your reply.

The antenna in question is for a GSM modem , I think the frequency is 890 MHz .

I have an N type to SMA female connector and was thinking having a short sma male to MMCX female cable or adaptor plugged into it. ( I have attached a picture showing the arrangement)

I would like to characterise the antenna when it is inside or outside the enclosure to see if it behaves any differently ( I'm a total newbie at this so this may not be possible)

Thanks again.
Nick

On Tue, Sep 22, 2020 at 01:23 PM, Reginald Beardsley wrote:

I found some discussion over a year ago, but nothing since. Has anyone done
this?

I had trouble finding any information on fixture design. Ultimately I settled
on biasing the candidate transistor with PCB edge SMA-F connectors on a board
and then with the appropriate appendages measuring it with the nanoVNA and
possibly some other VNAs.

I just made up a bunch of bare fixture boards. First up is a 2N3904 in CE
form and no feedback. After that I thought I'd try CB and CC before moving on
to feedback.

I know I'm not the only one interested, but I can't seem to find much record
of prior work.

Have Fun!
Reg

I just made up a bunch of bare fixture boards. First up is a 2N3904 in CE
form and no feedback. After that I thought I'd try CB and CC before moving on
to feedback.

One issue is the power level provided by the vna. At -12 dBm, unless padded, this is quite a large signal. The newer vna units I believe have the ability to adjust Pin lower. If the device is biased at low current, say 1 mA, then the thermal voltage is ~ 26 mV. You really need to keep Pin less than 1/10th of Vt or 2 mV and hence Pin of -30 dBm would be nice. At HF a typical BIP has an S21 of 40 dB. CH1 will overload. So now padding CH1 is required. However, S12 is lower than -40 dB so now we have a dynamic range issue. Getting s11 and s22 is not bad, since they are -10 and -3 dB typically.

So, how did you handle the CH0 power issue? Did you use pads, cal and then remove pads to finish up?

So it probably was good for more.

The exact ohmic resistance is not that important. 1% is good enough. I do prefer two 100 ohm resistors to reduce the inductance, but I would imagine they could be more fiddly to solder on than a single resistor.

All the supplied nanovna sma standards use only a single resistor. If you prise the top cap off the load, you can resolder two instead for improved top end performance. Also these loads all have only a 2% tolerance anyway. I have a half- decent set of N calibration standards and have managed to buy six (!) excellent Radiall standards, good to 6ghz for ?4 each on Ebay. The Forum standards expert Kurt Poulson has endorsed them. He and I may have now bought up the whole stock.

Steve L. G7PSZ

This might be useful.

In principle, it's easy. All you have to do is maintain a 50 ohm transmission line right up to the component leads. The devil is in the details.

Scanning from 50khz to 100mhz works much better than scanning 1mhz to 101mhz.

The 50khz to 100mhz scan showed a long stretch of 50 ohm cable,
it then rose to 100 ohms when it encountered a 100 ohm termination at the end
and stayed there for the remainder of the display as expected.

The 1mhz to 101mhz scan gave some rather confusing results.
The 100 ohm termination at the end of the 50 ohm cable got displayed as
a dip to 25 ohms and then back up to 50 ohms.
Also, the transitions were more rounded than the 50khz to 100mhz scan.
I guess it really needs to see that first low freq sample.

Perhaps this is related to John's observation of post 17593:
# If you set the Start frequency at half of the step size (say 15MHz to 3000MHz, 101 points),
# the impedance steps at the first (and every odd) "delay overflow" are inverted!!"

Jerry, KE7ER

Hello Steve,
I verified the kit only up to 1 GHz. It may be good up to 3 GHz (from connector spec).
In reality there are no standart 50 Ohm resistors You may find 49.9 or 51 Ohm.
Two 100 Ohm resistors give lower L value.

Regards Bert.

Scanning a cable from 1 to 101mhz, I see a horizontal scale on my nanovna-H4
of 390ns, which agrees with Neil's tmax = 39/fmax
I'll have to try John's Electrical Delay now, this is all starting to make sense.
Fun stuff!

Like everything nanovna, it's something you have to play with for awhile
before going out into the real world looking for trouble.

Jerry, KE7ER

Hi Dave-

It doesn't seem logical to differentiate between various Gamma, T-match, etc devices that are added solely to achieve an impedance match, and the use of lumped reactances like capacitors and inductors that are devices included for the exact same purpose. In either case, there is an "antenna system".

I think Walt Maxwell has taken a good view of the same situation from a different angle. His method works just fine and makes sense. That's not to say that looking at the "wires and rods" of the antenna separately from the matching network is "wrong", it's just different. And since both methods work just fine, neither would appear to be better or worse than the other. You prefer the approach taken by Krauss, Balinas and Jasik while I (and apparently some others) prefer Walt Maxwell's approach. We both achieve success, so there doesn't seem to be a problem! :-) It all just makes for a good discussion!

Very 73!

Tom AE5I

Dave - W0LEV wrote:

......Neither the Krauss nor Balinas or Jasik (which I do not have and wish I
did!) treatments address the circuitry to establish a match. All rigorous
antenna references (those two are my personal favorites) derive the feed
impedance and leave it there......

Yes, I have done this process more times than I can count! Over a frequency range from Hz to over 40 GHz.

Both small devices as well several hundred watt devices in various technologies.

All the prior references mentioned are excellent. I highly suggest G. Gonzalez textbook as well you should be able to find some wonderful treatments in the Applied Microwave magazine archives on line by Les Besser.

If I was you, I would fire up LT Spice. In LT you have some excellent spice models and for example the 2N3904 is in the library. LT does s parameters! Great tool. Now you can use spice to compare your measured s data against its model data. You will find your self em bedding its model into a fixture model that you will have to create. You need to be clever in creating this fixture model but once complete the agreement between measured and model is excellent. Finally consider how to do bias tees and provide a switching system that electrically turns the device end for end. Hence getting s22 and s12.

Alan