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22 : We Learn Our Lessons - NanoVNA Calibration
Considerations and Procedure_v1.1

@Gary O'Neil : /g/nanovna-users/message/3259

Hello,

Thank you very much for your time that you spent to
subjectively but kindly advice us lengthy about the
existed perfect climate that rein among the honorable
members of this forum !

We much appreciate that; indeed. Therefore, allow us,
please, to inform you that, as we already assured at:

18 : @Dr. David Kirkby : /g/nanovna-users/message/3192

and we can also gladly repeat here:

"
we always try to be good listeners, we shall also attempt
to follow your valuable subjective suggestions on this very
subject and to learn our lessons : Thank you once more !
"
On the occasion, allow us, please, to ask you to accept
our respects for your Excellent Work you have done into
the proven so valuable to us:

"NanoVNA Calibration Considerations and Procedure_v1.1"

where we read that :

"This document is mostly the work of Alan Victor, W4AMV
and his colleague Gary O’Neil, N3GO":
/g/nanovna-users/files/NanoVNA%20Calibration%20Considerations%20and%20Procedure_v1.1.pdf

Thanking you again,

Sincerely,

gin&pez@arg

I'd have wished they'd contact me about it instead, but as it's open
source, they are of course free to use the code.

I may need to make sure they don't reuse the name, though, so there isn't
confusion about which version is which.

Thanks for letting me know :-)
--
Rune / 5Q5R

Rune,
The popularity of NanoVNA Saver continues to grow. I just saw this over on the NanoVNA-F user group.

"We are currently modifying nanovna-saver (a good NanoVNA PC software) to fit NanoVNA-F, so stay tuned"

Good luck with them trying to keep up with your pace of development in a different branch :)

Herb

21 : The Mathematica Code and the Unpacked DERDEI Code

@Jose Luu : /g/nanovna-users/message/3278

Hello,

Thank you very much for your kind interest in our work !
We much appreciate that; indeed.

Especially, the fact that you spend your time to read our
documentation for our code. Therefore, allow us, please,
to inform you that, unfortunately enough, we are not in
place to fulfill your inquiry about our mathematica code,
which is already a more than ten 10 years old code ,
for an hierarchy of numerous reasons:

From the most generic first top one, which has to do with
the fact that meanwhile we radically changed our point of
view regarding proprietary software and thus we don't want
to support any one, in any way, even in our humble one,
anymore, down to the most specific last bottom one, which
has to do with the fact that this code is nothing more than
yet another example of the worst of programming style,
of a most personal character, that confused even us some
years ago, when we tried to find out what we had wrote
those days...

Well, after all that subjectively said, we conclude with our
definite decision : this mathematica code of ours is
definitely an unworthy, definitely a non-presentable,
definitely a not for publication code.

However, allow us, please, to also inform you that your inquiry
motivated us to decide that it is really now the time to unpack
the DERDEI code and distribute it, also under an MIT /F/L/O/S/S/
license, thus, we would like to please you to give us some time
to prepare the unpacked code in a form that will allow us to
decide that it is perhaps a somehow worthy, somehow
presentable, and thus a definitely publishable code.

Sincerely,

gin&pez@arg

21

Thanks for the info Warren,
73
de VU2PGB
VEEN

An update on dynamic range. In the photo the upper unit is the unshielded "worse" version and the bottom is the latest, best, shielded version. Both are calibrated for the 600 - 900 MHz range, Logmag, Ch1 with Through calibration. The reference level is the seventh level on both.

The diffenence in noise floor ranges from 3 - 10 dB across the range. Both units meet the dynamic range spec of 40 dB with the shielded unit showing better than 50 dB at the low end.

For my purposes the two units are substantially identical.

WA8TOD

is this modified software available to other users?

Gyula

All,

Thanks for the excellent information - so it does sound like step attenuator leakage is the culprit....which is not at all surprising given that it is a very cheap one ($40) that I purchased on Ebay earlier this year. I used it for some low power (-10 dBm to 10 dbM final RF output) WSPR mode experiments, typically at settings below 30 dB of attenuation, using an oscilloscope to verify the actual RF output power.

It's great to know that the dynamic range of the nanoVNA in the HF zone is as large as the S21 displayed values.


73,
Bruce

For those interested in the spectrum of the Si5351A here is a series of pictures, using my RFzero, at 267 MHz (i.e. 800 MHz "NanoVNA version"), 280 MHz, 298 MHz and 299 MHz. The pictures clearly show the behavior of the PLL and also the signal-to-noise performance.

More spectrum plots are here:

Bo

@Larry, Brian, DMR
In the meantime I have replaced the IP5303. Also the 10?F cap. But there is no improvement. The Nano still won't start on its battery.
The battery can be charged normally. I have placed the switch on pin 5 of the IP5303, so that I can start with the key-pin of the IP5303.
All proposals here do not improve. I also replaced the blue LED with a red one. A slightly increased load (+ 50 mA) with an additional LED or a resistor does not cause the IP5303 to start. All measured values ??appear normal.
But after 2 days there is a new phenomenon: after starting the Nano (via the IP5303 pin), it drops out after 7-8 seconds! I can repeat this endlessly, but it is always the same. Also with a full battery, also connected with the USB cable!
This way the Nano is no longer usable. I have no idea where this is coming from. There is no timer in the IP5303 that causes this? I have compared different schemes from IP53xx to IP5306, but they are all the same. The only difference I can find is that the coil (2.2?H) sometimes has a different value.
What could partly help me is that someone would post a detail photo of the components around the IP5303. Other experiences are also welcome.

No battery needed for saving calibration data, It is stored in flash memory

@ warren
Your nanovna is ver 3.1 printed on pcb with shields for three sections.
Is it the latest PCB Version.

Is internal battery necessary for saving Calibration data.
73
de VU2PGB
VEEN

Bruce

What you are seeing is leakage through your attenuator. Attenuators intended for HF work and below, especially those with a network of mechanical switches and resistors, often display this behavior. The higher the frequency the more the leakage around the attenuator.

Measurement of the Nanovna dynamic range is simply a matter of reading from the screen. It is defined as the difference between the level shown on the screen when port 0 is connected directly to port 1, and the level of noise shown in the screen with nothing connected to port 1. This would be measured using Logmag format and looking at CH1.

The dyhamic range decreases with frequency due to the output level from port 0 decreasing as well.

WA8TOD

I just did the experiment here with my hp 355D 100 dB attenuator/ 10 dB steps.

Attenuation is spot on and the VNA follows it just fine all the way down to 80 dB.
No surprises at HF.

If you have a COM receiver, certainly with sensitivity of better than -80 dBm and a sig gen,
try that combo and see if you have a defective step attenuator.

QSL. Alan

Hi Bruce.

Interesting. Well, I have measured HF filters whose center frequency is less than 30 MHz and readily saw skirt responses that were 80 dB below the pass band response. Now I made sure I took the 0 dB reference line to the very top of the display range. So with 8 divisions at 10 dB/division I would see the 80 dB attenuation point plus some noise.

Now the attenuator certainly could be limited in its true attenuation range if not properly constructed. Not easy to build 100 dB attenuators! Take a decent HP step attenuator, there not cheap when new! Could be leakage.

As a check, I'll try the same simple experiment at my end.

Alan

Hello yin&pez,

The software documentation mentions that there was a Mathematica version of
the software tools, even though the Matematica version may not be uptodate,
I am better at reading Mathematica code than fortran + maxima, I would like
if possible to have a look at the Mathematica code, could you upload it ?

Regards
Jose

I have a step attenuator with a series of switches (1-20 dB assorted values) that can be combined for (in theory) up to 80 dB total attenuation. Measuring the S21 individually, the 1,2,3,6,10,and 20dB switches yield S21 results on the nanoVNA that are very close to the stated values, testing over a 3-30 MHz frequency range. However, when I combine assorted switch values that sum to greater than 40 dB, the S21 results more or less max out at about -43 dB. On the other hand, the nanoVNA does displays S21 values in the -80 dB range with the step attenuator disconnected.

This makes we wonder whether the -43 dB maximum S21 result is a property of the step attenuator itself (internal leakage?), or is it simply the true dynamic range with my specific calibration, cables, connectors etc? Even 40 dB of dynamic range is plenty for my uses, and it seems like I find a new way to use this amazing device every day, but I am curious to learn more about what the dynamic range is.

On Sat, Sep 28, 2019 at 02:19 AM, Reginald Beardsley wrote:

Solving d = a*exp(j*2*pi*f*t) with 256 measurements will give better accuracy

Reginald could you please explain what means this equation? What means "d" and "a" variables?
It seems that "f" is frequency and "t" is time, but I'm not sure what frequency and time exactly?
If "f" is frequency of S11 point in frequency domain, then what means "t"?

Purchasing used cable is a very iffy business because hams tend to

leave cable in place for two decades and more. It should be changed out
regularly, of course.

A suggestion I would offer is to make Herb's observation below, of

course, for irregularities but also to measure the length physically and
then relate that result to what appears in the t.d.r. reflectometry. The
reason is dielectric contaminated by old formulation jackets and by
moisture and even overt water ingress. The author was called out to
investigate the station of a chap who was in a wheel chair because of
spina bifida. Disconnecting his coaxial cable at his transceiver
produced dribbling water! Presumably the installation up the tower at
his Yagi-Uda had been done incompetently or something had come adrift up
there. Anyway, the local ham club was called and the fellows came out
and ran in new cable for him and this time installed it properly up his
tower at the antenna.

Especially with all the estate sales we see these days, we should be

very suspicious of used coax for sale. It may be antique and in
deplorable condition. Physical length and velocity factor determined
length must agree. Meggering the cable would be a fine idea, too. See if
you can can beg, borrow or steal a megger for the day of the flea
market. If the seller won't let you megger the cable, then you know all
that you have to know about that piece of cable!

The cable is a capacitor, short it before connecting your analyzer.

John

at radio station VE7AOV

+++++


On 2019-09-27 2:38 p.m., hwalker wrote:

qrp.ddc,
Thanks for taking the time to reply. Ham's such as myself are generally looking to purchase specific types of 50 ohm cable such as RG-58, RG-223, RG-6 etc. The cables are all marked by the manufacturer according to type and we pretty much know the velocity factors by heart, so entering that info into the nanoVNA is a no-brainer. I don't really use the nanoVNA's TDR function for purchasing specific lengths, but rather to ensure for instance that a 10 meter length of cable being offered for sell doesn't have damage at say 4 meters to its inner conductor. One cable I measured before purchasing had very strange peaks and valleys on the nanoVNA's TDR function (wish I could have saved the screenshot), when I examined it more closely I could see slight equally spaced pits on its outer insulation. I'm guessing the cable was used in a mismatched power transmitting application and the spacing of the insulation pit marks was associated with the transmit frequency. So I use the TDR function as more of a sanity check to help sort the chaff from the wheat.

Sorry, I mistakenly assumed you had access to a professional level TDR to not appreciate how, even with its limits, the TDR function on the nanoVNA is a godsend to hobbyists, students, and radio amateurs as essentially a throw-in to its vector network analyzer capabilities. Let's hope in nanoVNA V2 that Hugen increases the number of measurement points and gives you some of the other things on your wish list.

Herb

--

Neat antenna response with the double frequency match.
They did a nice job.

Would be interesting to see how the radiation efficiency holds up.

Alan