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I updated the spreadsheet with a note, and removed the column that was confusing (just one of my experiments).

--
~R~
72/73 de Rich NE1EE
The Dusty Key
On the banks of the Piscataqua

On Sun, Jun 5, 2022 at 12:45 PM, AG6CX wrote:

Formula for cell “M4” shows = 20 x log10 (0.16), which actually calculates
to 20 x (-0.79588) = -15.917 dB

Actually, it's
-20 x log10 (0.016)
--
~R~
72/73 de Rich NE1EE
The Dusty Key
On the banks of the Piscataqua

Hello Roger,

I try to have zero extension after the calibration planes (at least for
30MHz). So I use SMA connectors with open, closed, load (2-100ohm SMD in
parallel) and through pins, see:

I do of course all my (Excel) calculations in the complex environment. And
I get the same results as the NanoVNA saver program for all values. I
plotted the |Z|, as It provides enough detail (certainly when having 10%
deviation;-).
For my S21 evaluation; my DUTs are normal resistors soldered on centre of
female SMA connectors (I don't care if the leads are long, all is my DUT)
and for comparing I use low frequencies (to minimise stray effects).

I use a slightly extended formula:
ZDUT(s) = 2*(Zsource+Zload)*((1/S21)-1)
Zload is the one measured with through connection to port 2 (S11
reflection).
Zsource can be manually varied in Excel for the evaluation (default 50ohms,
but can be any complex number).
Besie this, I also have Zo which is the reference of pure 50ohm (used in
the calucations/definitions). My Zo calibration load is 49.7ohm using DVM.

[image: afbeelding.png]

I need to measure impedances larger than 3 or 4kohm. as I am looking at
choking devices and I hope they have impedances above 5 or more kohm. And
frequencies upto the end of the HF bands (30MHz).
If I look at my DVM comparison with 1port S11 (reflection) results; even
21kohm provides ok-ish results (within 2%, which is good enough for me).

But I still want to understand why my 2port S21 Zduts are off some 9%.

When doing the 2port measurements, I get (as expected) similar impedance
values for impedance measuring Series S11 (minus Zload) and 1 port S11
reflection measurement. So this (S11) part of the 2port measurements can be
mapped nicely on the 1 port measurements.

Op di 7 jun. 2022 om 01:09 schreef Roger Need via groups.io <sailtamarack=
[email protected]>:

Next I attached the cable to Port2 (CH1) and measured the complex
impedance R +/-jX fro 10 kHz to 250 MHz. The attached plots show that
there is a considerable change in resistance over this range and an
unwanted capacitive reactance.

So in my case the difference is (using the through connector of my
calibration kit and from 330kHz to 30MHz).
[image: afbeelding.png]

My results are comparable to your 6dB attenuator results (I though have
this dip near low freqeuncies, I don't see this in a 50ohm calibration
load, so this is soemthing of my port2, I think...).

What I have not tested is how the impedance of Port1 (Ch0) varies with

frequency. This is not as easy a measurement and I have not done it. The
attenuator "trick" could be used here as well but needs further
investigation.

Owen Duffy mentions a method (). I also
did not do it (I though variate in my Exel to see the results and see if I
can map the NanoVNA measurmeent with the Excel).

What happens with the S21 series method is that as you increase the DUT
resistance you get more error in the S21 gain AND S21 phase. This
translates to larger differences in the expected complex impedance of the
DUT.

But 9%!? I am not able to simulate this in my Excel spreadsheet (except by
lowering Zload or Zsource to some 40ohm)... And would you not see the same
type of error in S11? (while that one is ok-ish).

I believe there are many sources of error such as the following:
- Port1 and Port 2 impedance is not 50 +j0 as pointed out above
- Stray inductance and capacitance of the test jig have a considerable
effect on the magnitude and phase of the S21 measurement. I have tried
several different test jigs and keep trying to improve. The attached photo
shows one I use but still needs work because the S11 reference plane is
too far from the DUT and I get an unwanted phase shift

For now I keep the freqeuncies of interest (for me) low: upto 30MHz.

- To calculate S21 the NanoVNA needs to know the power level generated on
Port 1. I have a hunch that this power level fluctuates as the Return Loss
decreases due to a higher DUT impedance.

Something like that must indeed happen.
The behavoir looks to be similar if the Zload is paralleled (so on port2
side) with an impedance (at least that is what I can see/simulate in my
Exel spreadsheet). But I don't think the port2 impedance does not change
much due to Zdut (I really hope!).
I tried to simulate volttage change of port 1 by varying Zsource (so a
change on port1 side): I can get a Zdut(2pseriesS21) equal to
Zdut(2pseriesS11) when Zsource=40ohms.
But the Zrefl (using 1 port S11 measurement) also will be changed due to
this change in Zsource. While that one was measured ok-ish...
So it is something, IMHO, on the port2 side...

I tried a 10dB at port2 to see the effects on Zdut. After recalibration I
get thee for 2port measurements:
[image: afbeelding.png]

The right bottom graphs compares Zdut with 10dB (red/darkblue) and without
10dB (orange/light blue). No significant change, so still this 9% error
compared to Zdut using S11 reflection measurement...

For more discussion on this topic here are some old post links...

/g/nanovna-users/topic/67738316#7993

/g/nanovna-users/topic/hardware_deficiencies_when/80639862?p=

With care it is possible to get S21 results that compare well with S11
measurements. Here is a post I made earlier on the subject.
/g/nanovna-users/message/24390. But I just use S11
method most of the time for ease of use.

Will digest these links.

Thanks.

All the best,


Victor

On 06/06/2022 19:54, gfmucci via groups.io wrote:

Version 1.1; Build Dec 21 2021.
Verbatim 16 GB micro SD card.
First formated Fat 32 via Windows 10 system. Wouldn't write from NANO.
Next installed "SD Card Formater" on my desktop. Did a full Fat 32 format. Wouldn't write from NANO.
Made sure to have NANO "off", then installed card, then turned NANO "on." No joy.
Suggestions?

Check the SD card with (for example):



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

On Mon, Jun 6, 2022 at 06:07 PM, Rich NE1EE wrote:

I have found (-H4, v4.3, DiSlord firmware v1.2)
1. I can hot swap the SD cards. No mounting, unmounting. I don't rush the
write ops, but it is clearly done when it says it is.

It is recommended in the NanoVNA beta group that you power off to install or remove SD cards. IIRC some cards have been permanently damaged by "hot swapping".

Roger

On 2022-06-06 11:54:-0700, you wrote:

Version 1.1; Build Dec 21 2021.

Verbatim 16 GB micro SD card.
First formated Fat 32 via Windows 10 system. Wouldn't write from NANO.
Next installed "SD Card Formater" on my desktop. Did a full Fat 32 format. Wouldn't write from NANO.
Made sure to have NANO "off", then installed card, then turned NANO "on." No joy.

I have found (-H4, v4.3, DiSlord firmware v1.2)
1. I can hot swap the SD cards. No mounting, unmounting. I don't rush the write ops, but it is clearly done when it says it is.
2. I tried a newer 32 GB card, and no joy. I happened to have an older one, and that worked. So now I am a one-card nVNA guy ;-) and I share it among my nVNAs.
3. There have been various discussions about the SD card requirements, but even if I understood them, the card specs don't seem to list what is needed.

~R~

I normally use the NanoVNA without the computer connected, and it matches
well with my MFJ analyzer.

When connecting to the computer today, I saw a similar issue when measuring
an HF multiband vertical (seemed to affect frequencies around 7MHz more
than others). The issue was resolved by putting a good ferrite bead on the
USB cable. Evidently, as others have noted, there can be RF on that cable
that needs decoupled.


On Mon, Jun 6, 2022, 4:51 PM Roger Stierman via groups.io <rogerstierman=
[email protected]> wrote:

Is the MFJ running on batteries? Or a wall wart?
Personally seen erroneous readings MFJ on wall wart, batteries are better.
Then check adapter/cable for NanoVNA.
Something is different in the RF path. Search, Grasshopper. WA0VYU

Sent from the all new AOL app for Android

On Mon, Jun 6, 2022 at 5:29 PM, Stefan<spommere@...> wrote:
Thanks.

How do you explain this:

MFJ: 1.8
NanoVNA not connected to laptop via USB-C: 2.7

Forget about the laptop, the USB-C cable, the NanoVNA Saver app .. but
just unplugging/plugging the coax among MFJ/NanaoVNA.

The MFJ is correct; I used it at another site last weekend, and compared
the reading to a $10k spectrum analyzer someone used there.

I went through several cycles of calibrating the NanoVNA, all with the
same result.

Version 1.1; Build Dec 21 2021.

Verbatim 16 GB micro SD card.
First formated Fat 32 via Windows 10 system. Wouldn't write from NANO.
Next installed "SD Card Formater" on my desktop. Did a full Fat 32 format. Wouldn't write from NANO.
Made sure to have NANO "off", then installed card, then turned NANO "on." No joy.

Suggestions?

Is the MFJ running on batteries?? Or a wall wart?
Personally seen erroneous readings MFJ on wall wart, batteries are better.
Then check adapter/cable for NanoVNA.
Something is different in the RF path.? Search, Grasshopper. WA0VYU

Sent from the all new AOL app for Android

On Mon, Jun 6, 2022 at 5:29 PM, Stefan<spommere@...> wrote: Thanks.

How do you explain this:

MFJ: 1.8
NanoVNA not connected to laptop via USB-C: 2.7

Forget about the laptop, the USB-C cable, the NanoVNA Saver app .. but just unplugging/plugging the coax among MFJ/NanaoVNA.

The MFJ is correct; I used it at another site last weekend, and compared the reading to a $10k spectrum analyzer someone used there.

I went through several cycles of calibrating the NanoVNA, all with the same result.

1. I cannot get "VSWR" to start / display anything reasonable , BUT "return loss" works as expected
2. How do I delete "marker" - say delete all markers? (I hate clutter)
3. moving mouse wheel zooms "vertical display " , how do I "unzoom "? "
4. is the app missing "save" buttons ( any change ) intentionally ?
5. Can the "sweep " be sped-up ? (serial port baud rate ?)

On Mon, Jun 6, 2022 at 02:56 AM, Victor Reijs wrote:

I have also checked my NanoVNA.
If I measure the Zload of port 2 (using Port 1, so using a calibration
Through connection and measuring port2's S11). I get the following |Zload|
of port 2:
[image: afbeelding.png]
This is ok-ish IMHO (variation some 0.1ohm (less than 0.2%). There is a
deviation from 50ohm (around 05%), but this could be partly due to
inaccuracy calibration Load (measured with DVM: 49.7ohm).
I don't think the Zload (|Z| of port2/load) is problematic.

The calculations for S21 series method are based on the Port1 (Ch0) and Port2 (CH1) impedances Zref being 50+j0 (not |Z| = 50). See attached equations.

I used the 15 cm Cable that came with my -H4 and calibrated it using SMA loads. The DC resistance of the 50 ohm load was 49.87 ohms. I then calibrated at the end of this cable to establish the reference plane (photo attached). Next I attached the cable to Port2 (CH1) and measured the complex impedance R +/-jX fro 10 kHz to 250 MHz. The attached plots show that there is a considerable change in resistance over this range and an unwanted capacitive reactance. One "trick" that works is to use a quality SMA attenuator and attach it to Port2 (CH1) and this will give a better impedance match. I have a good 6 dB one and you can see the improved performance with it attached. When calibrating for S21 with it attached you get a better impedance match but reduce the S21 dynamic range by 6 dB.

What I have not tested is how the impedance of Port1 (Ch0) varies with frequency. This is not as easy a measurement and I have not done it. The attenuator "trick" could be used here as well but needs further investigation.

If I measure metal resistors (averaged between 300 and 1800kHz) using
Reflection and Series S21 I method, I get the below |Z| values. I also give
the R values measured with DVM

So indeed |Zrefl| does not deviate much from the DVM value (<2%). The
|ZseriesS21| though differs quite a lot (~9%) from DVM value and looks to
be proportional to the resistor value

Yes the S11 reflection method gives good results at resistances in the thousands of ohms. What happens with the S21 series method is that as you increase the DUT resistance you get more error in the S21 gain AND S21 phase. This translates to larger differences in the expected complex impedance of the DUT.

Where is this 9% error coming from? A 9% error is large! I don't think the
deviation of the port2 load (Zload) from 50ohm is problematic (only some
0.2%). Looking at the Zsourse (the impedance of port 1): would that not be
close to Zload (impedance of port2, I hope/assume...). But that one is
compensated using the SOLTI method, or not?

I believe there are many sources of error such as the following:
- Port1 and Port 2 impedance is not 50 +j0 as pointed out above
- Stray inductance and capacitance of the test jig have a considerable effect on the magnitude and phase of the S21 measurement. I have tried several different test jigs and keep trying to improve. The attached photo shows one I use but still needs work because the S11 reference plane is too far from the DUT and I get an unwanted phase shift
- To calculate S21 the NanoVNA needs to know the power level generated on Port 1. I have a hunch that this power level fluctuates as the Return Loss decreases due to a higher DUT impedance.

I understand the missing of 12-term correction is the other problem (as
stated by Owen Duffy: ). Who has a
procedure for this? I could not find this on the web (Owen Duffy refers to
it, but I don't see a procedure).

For more discussion on this topic here are some old post links...
/g/nanovna-users/topic/67738316#7993
/g/nanovna-users/topic/hardware_deficiencies_when/80639862?p=

With care it is possible to get S21 results that compare well with S11 measurements. Here is a post I made earlier on the subject. /g/nanovna-users/message/24390. But I just use S11 method most of the time for ease of use.

Roger

Another case which will result in varying readings is a vertical antenna (e.g for a handheld) which is lacking a ground/counterpoise/ground plane/feedpoint choke; then the measurement system becomes part of the antenna's ground. End fed antennas often have considerable feedline currents which will affect the readings.
Use the VNA in the state it was calibrated in, for antenna work probably best to use the battery and leave the charger disconnected, or add chokes/ferrites etc. You may need ferrites on both feedline and charger cord, it is hard to predict.
You might want to set the VNA down on a nonconductive stool or table for use, to avoid body effects on antenna measurements.
73, Don N2VGU

In some applications a square wave can be beneficial. Many mixers will perform better with a square wave LO than with a sinusoidal one.
73, Don N2VGU

Thanks.

How do you explain this:

MFJ: 1.8
NanoVNA not connected to laptop via USB-C: 2.7

Forget about the laptop, the USB-C cable, the NanoVNA Saver app .. but just unplugging/plugging the coax among MFJ/NanaoVNA.

The MFJ is correct; I used it at another site last weekend, and compared the reading to a $10k spectrum analyzer someone used there.

I went through several cycles of calibrating the NanoVNA, all with the same result.

When I have this problem it’s usually because I’m getting RF coming back on the shield, I put a couple of clamp on fairite chokes on or coil the coax and I get good readings again. Just an idea.
73 Bill N7OQ

This has been addressed a number of times in this group. If you cal
without the USB cable connected and then connect it for a measurement of
your unknown, this is quite expected. The case of the VNA is "extended" by
the presence of the USB cable and interacts with the unknown, especially if
it is a radiating structure.

Dave - W0LEV

--
Dave - W?LEV

Very happy you were able to resolve your issue73's

Possibly a ground loop thru the USB-C. Try running the laptop from its battery, no recharging PS.
WA0VYU

Sent from the all new AOL app for Android

On Mon, Jun 6, 2022 at 1:19 PM, Stefan<spommere@...> wrote: Hi,

I have a MFJ-259B antenna analyzer and now also a NanoVNA-H, along with the NanoSaver App.

I get inconsistent VSWR readings with both devices:

MFJ: 1.8
NanoVNA not connected to laptop via USB-C: 2.7
NanoVNA connected to laptop via USB-C: 1.1

The VSWR reading on the NanoVNA literally goes from 1.1 to 2.7 when I unplug the USB-C cable from the NanoVNA.?
I went through call calibration steps at least a half dozen times on the NanoVNA for 50kHz to 900MHz, and for the 40m band (7.0 MHZ - 7.3 MHZ).

Any suggestions as to what value I should actually trust ?
I wonder if I need to calibrate the NanoVNA through the Saver app separately; based on what I've gathered, it should not be necessary.

Thanks for any advice.

Hi,

I have a MFJ-259B antenna analyzer and now also a NanoVNA-H, along with the NanoSaver App.

I get inconsistent VSWR readings with both devices:

MFJ: 1.8
NanoVNA not connected to laptop via USB-C: 2.7
NanoVNA connected to laptop via USB-C: 1.1

The VSWR reading on the NanoVNA literally goes from 1.1 to 2.7 when I unplug the USB-C cable from the NanoVNA.
I went through call calibration steps at least a half dozen times on the NanoVNA for 50kHz to 900MHz, and for the 40m band (7.0 MHZ - 7.3 MHZ).

Any suggestions as to what value I should actually trust ?
I wonder if I need to calibrate the NanoVNA through the Saver app separately; based on what I've gathered, it should not be necessary.

Thanks for any advice.

Thanks Chris, finally figure it out it was the driver all the time.