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The vertical scale is the abs of the measured s11. Zero to one. Red an green lines
The pink line is S11 open phase minus S11 short phase minus pi.
What would the offset delay do to the rotation of S11 open and short. Would it impact the phase or also the magnitude.
Would it be constant shift or frequency dependent?

On Tue, 29 Oct 2019 at 19:41, <erik@...> wrote:

David

You are very right. C0 is only that high after the optimization because of
other problems but I can not find them.....

What are you using as the calibration standard that you are trying to
optimise? Are you trying to optimise the male open supplied with the kit?
Or creating a female open by putting that open on the end of an adapter? If
you are, remember that adapter supplied with most kits is very poor. I have
not measured the delay of it, but I would guess around 50 ps.


--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

Did you performed CAL RESET before screenshot?

Yes, and also disabled CAL-CORRECTION

It looks not good. With such hardware you may have worse dynamic range.

Yes, Hugen warned of such, but note SCALE is 12dB/div with 0db at 8
I have been going to run some noise abatement experiments.

It looks that original hugen79 hardware has really better performance.

"...they [clones] have failed to understand the role of bridge and shielding,
and made some bad modifications to facilitate manufacturing."
/g/nanovna-users/message/158

On Tue, 29 Oct 2019 at 18:22, Mel Farrer, K6KBE <farrermesa@...>
wrote:

On the Smith Chart, the short is at 9 o'clock and the open is at 3
o'clock. This is the way it is supposed to be. 180 degrees.

Mel, K6KBE

180 degrees phase difference between open and short gives you the best
stability in the calibration. However, the inductance of short is
negligible, but the fringe capacitance of the open is not. So you will *not*
get 180 degrees if you short and open a bit of coax. It will be close, but
certainly not 180 degrees.

Despite all these idiots on YouTube and elsewhere telling you that the
short needs to be as short as possible, the delay of the short should be a
little longer than the open, in order to get as close as possible to the
180-degree phase difference.

Picking one of the cal kits I have, the Agilent 85052B 3.5 mm, which is
nearest to SMA, the offset delays are

* Shorts = 31.785 ps
* Opens = 29.243 ps


--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

With that little number or points it is impossible to judge noise. Try at least 100 points

On Tue, Oct 29, 2019 at 09:38 PM, Oristo wrote:

nanoVNA "worse" clone. This is the first time it has 50 Ohms directly to its
SMA since July.

Did you performed CAL RESET before screenshot? It looks not good. With such hardware you may have worse dynamic range.

It looks that original hugen79 hardware has really better performance.

David

You are very right. C0 is only that high after the optimization because of other problems but I can not find them.....

On Tue, 29 Oct 2019 at 18:28, <erik@...> wrote:

The manual optimization took way too much time so I learned how to do
non-linear least squares multiparameter fit in Octave. The created Octave
scripts are attached. Loaddata.m loads the uncalibrated datasets. optim.m
runs the optimization to minimize the residue (residue.m) by repeating
calibration (calib.m) with tuned parameters. Don't complain about my
ineffective use of Octave. This is my second day of usage

What is on the y-axis of your graphs?

There's absolutely no way that C0 should be as high as 500. Someone
recently showed for that Keysight kits, having just a delay and C0 was
sufficient at 1500 MHz or so. So forget C1 for one minute, and just worry
about

1) Get the offset delay right - assuming C0=C1=C2=C3=0
2) Optimise for a value of C0

Look at the values on the Keysight website



to give you some idea of the typical values of C0. There are tons of kits
there, so I will list the first 3 I have, but plus one with a smaller
connector.


*85050B 18 GHz APC7. *
This since is genderless, there is no male or female.
C0=90.4799

*85054B 18 GHz type N*

C0=89.939 (male open)
C0=104.13 (female open)

*85852B 26.5 GHz 3.5 mm, so closest to SMA. *

C0=49.433 for both male and female.

*85056A 50 GHz 2.4 mm (I don't have such a kit, but I will just list it, as
its a smaller than 3.5 mm connector)*

C0=29.722 (male open), 29.72 (female open)

Your coax could have quite a loss at the top end, which means a complex
value (by complex, I do mean real and imaginary) of characteristic
impedance.

You would be better with a length of RG401 (6.3 mm OD), but if not, the
cheaper RG402 (3.5 mm OD). Those would have lower loss than your RG58.

But you seem to be ignoring any offset delay, and without that being
somewhere near correct, it is pointless worrying and C0, C1, C2 or C3.

What is your calibration standard? Is it the standard male open supplied
with the NanoVNA? If so, I could give you some sensible starting values.

Dave

--
Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892

Tel 01621-680100 / +44 1621-680100

Look at the purple line in this chart
/g/nanovna-users/attachment/5975/1/fit_end.PNG
It's the deviation from 180 degrees versus frequency after optimizing the fringe capacities

The same screenshot (CH0 LOGMAG and CH1 LOGMAG after CAL RESET)
for other devices are also welcome,
it will allows to get statistics about RF frontend on different devices

nanoVNA "worse" clone. This is the first time it has 50 Ohms directly to its SMA since July.

version
0.4.2-bf9c4ba-release

trace
0 LOGMAG CH0 12.000000000 8.000000000
3 LOGMAG CH1 12.000000000 8.000000000

10k - 1500M

These are 1020 point measurements. There are no spikes nor noise

larry36, at a glance looks good, but it seems that your hardware has some issues above 1200 MHz.

Here is mine:

Two adf4351 modules. One at two GHz into LO port of mixer and the other at 2 till 3 GHz through 3 GHz low pass filter an 10 dB attenuator into RF port of mixer. The IF port should output a acceptable sinus from 0 to 1 GHz
That is what I did

I don't think of this as a screen protector. It looks like the film commonly seen on on much newly purchased electronics. I think its just to keep smudges off during final assembly and shipping. The Nano is just unusual (unique?) in that they screw the bezel on over the film. Perhaps the display or electronics sub-assemblies arrived with the film in place and final assembly just adds the battery, standoffs, back cover and bezel without removing the film. I have a couple of these and on one I just worked the film off from under the bezel. On another, I removed the bezel screws - that was easier. If you are a screen protector kind of person, you might do well to buy or salvage one and cut it to size. Real screen protectors are tougher than this film.

I'm used average for calibration and it works great. But it takes more time for measurement. So I upload firmware with average, calibrate it with disconnected USB cable and then upload normal firmware. With such kind of calibration I got much better calibration with no random spikes. :)

CH0 50 OHM
CH1 50 OHM

The manual optimization took way too much time so I learned how to do non-linear least squares multiparameter fit in Octave. The created Octave scripts are attached. Loaddata.m loads the uncalibrated datasets. optim.m runs the optimization to minimize the residue (residue.m) by repeating calibration (calib.m) with tuned parameters. Don't complain about my ineffective use of Octave. This is my second day of usage.
With every optimization pass the updated calibration correction parameters are used to do a S11 calibration at reference plane and then the S11 open/short/load of a 1 meter coax is corrected using the determined calibration
The initial run delivers the first picture. This is the 1 meter coax after calibration at reference plane with uncorrected calibration parameters.
The target is to get a S11 open/short of a 1 meter coax to behave well, e.g. the abs(S11) should decent linear with frequency starting at 1 (red and green lines)
The blue line is the abs(error) for that frequency and as you can see the error is suggesting there is a very systematic error somewhere
Then I spend considerable time to have Octave search for the best calibration model correction parameters and I finally settled for only two: OpenC0 and OpenC1 (see second picture). The Load and Short Length did not make any relevant difference.
As you can see the error at lower frequencies is not reduced and it is almost as if the original non-corrected S11 open/short rotate with an constant offset. because their abs error rotates with constant amplitude and speed
So now I am stuck. There must be a systematic error the causes most of the observer errors in the 1 meter coax measurement but this error can not be optimized out with the current model I am using.
Any suggestions of what I am doing wrong?

On the Smith Chart, the short is at 9 o'clock and the open is at 3
o'clock. This is the way it is supposed to be. 180 degrees.

Mel, K6KBE

The same screenshot (CH0 LOGMAG and CH1 LOGMAG after CAL RESET) for other devices are also welcome, it will allows to get statistics about RF frontend on different devices