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Erik,
There was a discussion on one of the Russian user groups regarding the isolation calibration. The Goggle translation is below:

"The original calibration procedure said that for better calibration, the load should not only be connected to CH1, but also to CH0. That is, for good isolation you need to use two loads. But because there is only one load supplied with the kit, the best procedure is to connect it to CH1 And CH0 leave open.

As the saying goes, it's enough to just think - there's no point in plugging in a CH0 load to measure ch1 channel insulation. To measure the insulation of the CH1 channel, the Terminator is logically connected to the CH1 channel. However, given the dynamics of NanoVNA, this error will not have much impact on the results. When calibrating ISOLN with an open CH1, you'll just get a slightly bigger margin of error when measuring s21 due to the increased noise on CH1 at the time of ISOLN calibration. You may think that instead of eliminating the insulation error, you added an error instead.

Here's a quote from the original instructions:

Isolation calibration of CH 1 requires two loads of loads to connect CH 0 and CH 1,respectively, to obtain the best isolation, usually with only one set of calibration loads for port 0, and to connect the load calibrator to CH 1, CH 0 to remain open , and then press the ISOLN menu to calibrate.

In summary, calibrating the CH1 channel insulation for the best result requires connecting two loads to both CH0 and CH1 channels, usually with only one load for the CH0 port, connect this load to the port CH1, and leave the CH0 port open and press the ISOLN menu for calibration. "


My own opinion is that the order of the nanoVNA calibration menu is such that the 50 ohm load is still on ch0 when you get to the isolation step, so it may not be worth the added accuracy to move the load to CH1 unless you just want to be more precise. I have two 50 ohm loads so I actually use one each on CH0 and CH1 when performing an isolation calibration.

Greetings,

Thanks for the info!

I should have mentioned that for doing these tests I did not use the supplied SMA calibration references. I have a set of DIY BNC references that exhibit a shunt capacity of about 0.5 pF which is rather insignificant considering the test capacitor is 30 pF. Thus the calibration was done with the BNC connectors connected. The OPEN included an empty BNC of the same design. Additionally at 150 MHz the lengths are not quite so critical. I might re-do this test some day with a precision SMD capacitor which would be better than the high quality leaded silvered mica that I used.

The TDR test results looks interesting! I have not tried out my NanoVNA in TDR mode yet.

Enjoy!
Tom
VA7TA

Perfect, thank you!

If you calibrate using a cable and female-female and SHORT/OPEN, you should use the same cable and female-female for LOAD, all connected to CH0
If you calibrate without cable connect OPEN/SHORT/LOAD directly to the CH0 SMA

Yes

I've read and tried to follow the calibration instructions listed in the "Files" section of this group. When I get to "Note 13," to calibrate LOAD, it instructs me to use a second 50 ohm terminator and second F-F adapter, which were not included and I do not own.

In this case, should I just put the included load on CH0 (S11)?

Thanks, and 73--
Mark, K0NIA

qrp.ddc@ wrote ...

Here is also TDR impedance measurement for this transmission line. You can see 1 meter RG58 cable with BNC connectors from 4.7 to 15.1 ns.

qrp.ddc,
Can you point me to the mod of the nanoVNA software that contains the two TDR measurement options that you used? The link you provided earlier at SDR-RTL does not include those options.

Here is also TDR impedance measurement for this transmission line. You can see 1 meter RG58 cable with BNC connectors from 4.7 to 15.1 ns.

Bruce

For S21 "Through" measurements the only parameter that needs to be calibrated is the Through. Short, Open, and Load will not affect your results. BUT!......... be sure to Reset before performing the through calibration.

Larry

To date I have owned or used five Nanovna and all have been from different manufacturers. I do not see any cases where the out of the box characteristics vary wildly and, in fact, when calibrated using the same loads all produced results with negligible deviation. From my experience to date the distinctions among the different units being sold are insignificant.

Warren Allgyer
WA8TOD

Also note, that Chinese BNC connectors have bad SWR. For example, here is TDR VSWR measurement for transmission line with two BNC connectors on RG58 cable with 50R terminator at the end of transmission line. As you can see two BNC connectors have ripple up to VSWR=1.08.

PL-239 has even worse ripple up to VSWR=1.2

Tom VA7TA, it drops down, because you didn't compensated transmission line delay (signal delay in BNC connector). If it different at least 1 mm than calibration kit, you will get different values.

For example here is measurement of 500 Ohm terminator. The terminator is connected through SMA-SMA adapter, so the transmission line is about 15 mm longer than calibration kit terminators. The first picture shows measurement as is, with no electronic delay compensation. The second picture shows measurement with 242 picoseconds electronic delay enetered into NanoVNA menu.

As you can see there is very significant difference in measurement result at high frequency.

you can find electronic delay of transmission line with no match on the end with Group Delay screen. Then you can enter it in the ELECTRONIC DELAY menu in the NanoVNA.

Hello,

Thank you very much for your interesting suggestions !

Sincerely,

yin&pez@arg

Bruce,
That is exactly what I do when I want to quick check the gain of an rf preamplifier. Running a "through" calibration prior to S21 testing normalizes your test set-up, basically zeroing out any in-line connecting cables and attenuators, before the S21 sweep of your filter or coax line.

you're needs to setup electronic delay compensation in the NanoVNA to eliminate that curve. it happens because your load connected with different transmission line length than calibration kit load.

For example, here is 500 Ohm load measured with NanoVNA. First picture is how it looks with no electronic delay compensation. And the second picture is how it looks with electronic delay compensation 242 picoseconds entered into NanoVNA. (242 ps = 15 mm connector)

NanoVNA software which allows to see series and parallel RLC charts, can be found here:

On Tue, Sep 17, 2019 at 07:05 AM, Bruce KX4AZ wrote:

Sometimes I just want to quickly check a filter or coax line for its "through
transmission" properties, i.e.a log S21 plot. Is it necessary to do the full
SOL calibration in addition to a "thru" measurement to get an accurate S21
plot in that situation?

Bruce,
The nanovna is a very useful hobby device but due to the many manufacturers churning them out, out-of-the-box characteristics can vary widely.
The easiest thing to do is to perform a wide-band calibration (where you're using it most of the time., ie: 50K-200M) using the cables and save it to location 0.
Location 0 is loaded every time you turn on the unit so at least you'll have a default cal to use for quick checks.
For the times when you want to check items at a different freq, you can then cal for that.

73
Larry

Hello Erik

Some progress using Wine 4.0.2 on Mint Linux 19.2.

Created a new 32-bit wine prefix.

Used winetricks to install vcrun2010, dotnet40, dotnet45, dotnet46, dotnet461. Used dotnet_verifier to test dotnet installation.

Created a symbolic link from COM10 to /dev/ttyACM0.

VNAR4.3 runs but cannot connect to the nanoVNA.

What baud rate, # of bits, parity, # of stop bits does VNAR4.3 assume?

Nick

Sometimes I just want to quickly check a filter or coax line for its "through transmission" properties, i.e.a log S21 plot. Is it necessary to do the full SOL calibration in addition to a "thru" measurement to get an accurate S21 plot in that situation?

For those who have previously had problems with using newer 10k-1500M
firmwares with NanoVNA-Saver (or other crash issues): On GitHub, the latest
version of the master branch now has a debug function: Use the command line
option '-d' to see debug info, and '-D filename.log' to save debug info to
a file, which you can send to me if you see crashes.

This should help me be able to find out what's going wrong when you see
these crashes.

It will also be included in the next release, including in the Windows
.exe, which will be out this week, maybe tomorrow.

Thanks,
--
Rune / 5Q5R

On Sat, 14 Sep 2019 at 11:45, David J Taylor via Groups.Io <gm8arv=
[email protected]> wrote:

Yes, I've heard someone else mention that. I can't quite think what causes
it, *assuming* the firmware didn't change the format of the commands used.
I currently just have the one NanoVNA, and as I need to use it for
development, I have been a bit reluctant to flash experimental firmware on
it. I may have to try :-)

Rune / 5Q5R
=====================================

Yes, I also have just the one, and that was the first time I'd flashed new
firmware. I was hoping that getting back to a known working version
wouldn't be too difficult if I did need to do that! The flashing is very
quick.

73,
David GM8ARV
--
SatSignal Software - Quality software for you
Web:
Email: david-taylor@...
Twitter: @gm8arv

Greetings All,

To test the imaginary high impedance measurement accuracy of the NanoVNA I decided to use a high quality precision capacitor. The best precision capacitor I had on hand for the job was a leaded silvered mica 30pF +/- 0.5pF type. I kept the connection leads to the BNC connector as short as possible.The results from these tests will also reflect the measurement accuracy for inductance which of course would be of opposite sine. As there is no such thing as a pure inductance because of wire resistance, distributed capacity and self resonance characteristics it is not practical to attempt to use an inductor for measuring the capability of the NanoVNA.

I chose to set the sweep to cover 1 MHz to 150 MHz. I limited the high end of the sweep to avoid influence from lead inductance which causes series resonance to occur around 320 MHz. The reactance range for the selected sweep width extends from 5462 Ohms at 1 MHz down to 28 Ohms at 150 MHz. The capacitor measured 29pF at 1 MHz, 31pF @ 50 MHz and 37pF at 150 MHz. Attached are screen captures and s1p files for the calibration steps and measurement. Accuracy at 1 MHz to 50 MHz was within about 3% with the Z 5.5K at the low end. Accuracy deteriorated to 10% at about 100 MHz then dropped off further to 20% at 150 MHz.

It is interesting that according to these test results the shunt measurement method seems also capable of accurately measuring a moderately high imaginary impedance with very little real component. Good news for most of my applications. It appears as if the shunt measurement method accuracy capability is not limited to just a few hundred Ohms for lower frequencies.

Enjoy!
Tom
VA7TA