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Re: At which point do we take the value of impedance to tune an antenna?

 

Yes!!! Learn the Smith Chart!!!! Also, learn and internalize Ohm's
Law!!!! Both will serve you well with all things RF.

SWR can be measured as current, or voltage standing wave ratios.

A good test for all this confusion is to establish a system which measures
1:1 SWR at a known frequency. Then add an electrical 1/8 to 1/4-wavelength
of transmission line to the system. If the SWR remains 1:1 with the added
transmission line in place, indeed, the SWR is 1:1. If the measurement
with the additional line length measures something other than 1:1, the
original 1:1 measurement is in error. This is the primary reason
S-parameters deal strictly with power, the product of voltage and current
for a sine wave. With SWR on the transmission line, voltage and current
along the line changes as measured at single points along the line.
However, power remains the same along the line - it's just Ohm's law with a
little very simple algebra.

Dave - W?LEV

On Wed, Aug 3, 2022 at 4:10 PM Kenneth Hendrickson via groups.io <dsp_stap=
[email protected]> wrote:

Russ,

If the load is not perfectly matched to the source, there will be a
voltage standing wave ratio (VSWR) because of the mismatch.

Learn the Smith chart.

On Wednesday, August 3, 2022, 11:52:31 AM EDT, Russ <
u.rusty@...> wrote:

On Tue, Aug 2, 2022 at 05:26 PM, Jerry Stuckle wrote:


The VSWR is based on impedance - which is a combination of resistance and
reactance.
Can you explain this in more detail. I thought VSWR was based on voltage.











--
*Dave - W?LEV*
*Just Let Darwin Work*


--
Dave - W?LEV
Re: At which point do we take the value of impedance to tune an antenna?

 

Helpful document:

On 8/3/2022 9:10 AM, Kenneth Hendrickson via groups.io wrote:
Russ,

If the load is not perfectly matched to the source, there will be a voltage standing wave ratio (VSWR) because of the mismatch.

Learn the Smith chart.

On Wednesday, August 3, 2022, 11:52:31 AM EDT, Russ <u.rusty@...> wrote:
On Tue, Aug? 2, 2022 at 05:26 PM, Jerry Stuckle wrote:

The VSWR is based on impedance - which is a combination of resistance and
reactance.
Can you explain this in more detail. I thought VSWR was based on voltage.
Re: At which point do we take the value of impedance to tune an antenna?

 

Russ,

If the load is not perfectly matched to the source, there will be a voltage standing wave ratio (VSWR) because of the mismatch.

Learn the Smith chart.

On Wednesday, August 3, 2022, 11:52:31 AM EDT, Russ <u.rusty@...> wrote:

On Tue, Aug? 2, 2022 at 05:26 PM, Jerry Stuckle wrote:


The VSWR is based on impedance - which is a combination of resistance and
reactance.
Can you explain this in more detail. I thought VSWR was based on voltage.
Re: At which point do we take the value of impedance to tune an antenna?

 

SWR = Zt / Zo applies only when both impedances are resistive. When Zt = 40 +
j30 ohms, the load is highly reactive. The coefficient of reflection rho is:

rho = (Zt - Zo) / (Zt + Zo) = 0 + j0.3333 ...

SWR = (1 + abs(rho)) / (1 - abs(rho)) = 2.0

73,

Maynard
W6PAP



On Tuesday, August 02, 2022 05:26:38 PM Jerry Stuckle wrote:
Incorrect. The VSWR is based on impedance - which is a combination of
resistance and reactance. A vertical at resonance will have an impedance
of about 35 + 0j ohms or an impedance of 35 ohms and a 50/35 or 1.43:1 SWR.
However, slightly off resonance it could have an impedance of say 40 + 30j
ohms, which would have a total impedance of 50 ohms (just an example for
ease of calculations) and an SWR of 1:1. The antenna is non-resonant at
the lowest SWR reading.


-----------------------------------------
Re: At which point do we take the value of impedance to tune an antenna?

 

On Tue, Aug 2, 2022 at 05:26 PM, Jerry Stuckle wrote:


The VSWR is based on impedance - which is a combination of resistance and
reactance.
Can you explain this in more detail. I thought VSWR was based on voltage.
Re: At which point do we take the value of impedance to tune an antenna?

 

40+j30 is a Z of 50 ohms. In this case, this is an SWR 1:2 !!! Not 1:1 .

Only swr 1:1 is 50 ohms resistive load (and then again, using a 50 ohm cable ;-) ).


73

Arie PA3A

Op 3-8-2022 om 02:26 schreef Jerry Stuckle:

Incorrect. The VSWR is based on impedance - which is a combination of resistance and reactance. A vertical at resonance will have an impedance of about 35 + 0j ohms or an impedance of 35 ohms and a 50/35 or 1.43:1 SWR. However, slightly off resonance it could have an impedance of say 40 + 30j ohms, which would have a total impedance of 50 ohms (just an example for ease of calculations) and an SWR of 1:1. The antenna is non-resonant at the lowest SWR reading.
Re: At which point do we take the value of impedance to tune an antenna?

 

Incorrect. The VSWR is based on impedance - which is a combination of resistance and reactance. A vertical at resonance will have an impedance of about 35 + 0j ohms or an impedance of 35 ohms and a 50/35 or 1.43:1 SWR. However, slightly off resonance it could have an impedance of say 40 + 30j ohms, which would have a total impedance of 50 ohms (just an example for ease of calculations) and an SWR of 1:1. The antenna is non-resonant at the lowest SWR reading.
Re: At which point do we take the value of impedance to tune an antenna?

 

Note that when the load looks resistive the VSWR versus frequency is at a minimum.

On August 2, 2022 4:38:51 PM MDT, W0LEV <davearea51a@...> wrote:
And please remember resonance is not necessarily at 1:1 SWR. It may or may
not be. Resonance is *defined* by (consult the complex portion of the
measured impedance): +jX = -jX. The resistance term is purely resistive
(consisting "mostly" of the radiation resistance) while the reactive
component is strictly reactive: capacitive or inductive.

Dave - W?LEV

On Mon, Aug 1, 2022 at 10:01 AM Diane BONKOUNGOU <dianebonk2@...>
wrote:

Hello Roger,
Thanks for reminding me, I will post on the other topic how I went about
correcting the electronic delay introduced by the SMA cable. My cable was
too long to correct the electronic delay at its end after doing the
calibration at the NanoVNA end that's why I had a lot of circles in the
Smith chart. I cut the cable further and have a quarter circle in the Smith
chart and then use the Edealy parameter in the NanoVNA to correct.
Best regards

Le ven. 22 juil. 2022 ¨¤ 17:03, Roger Need via groups.io <sailtamarack=
[email protected]> a ¨¦crit :

On Fri, Jul 22, 2022 at 04:34 AM, Diane BONKOUNGOU wrote:


Hello,
Hi, I am a beginner in antenna design and tuning.
I want my antenna to have a resonant frequency of 2.45GHz for
low-energy
Bluetooth communication.
And I want to know what to consider for the matching process.
I have made some measurements with Nanovna of my antenna. I have a
resonance
frequency of 2.28GHz and at this frequency, I have an impedance of
47.8-7.06j.
Can I take the value of this impedance at this frequency for the
matching
process or do I have to take the value of impedance at 2.45GHz?
Where to take the value of impedance for tuning?
Thanks.
You never posted in the other topic what you finally did to correctly
measure the antenna with the NanoVNA. If you don't establish the
"reference plane" rightat the antenna your impedance measurements will be
way off and you won't be able to design a matching network. Even if you
get a decent "reference plane" the antenna must be measured in circuit so
that you have a the same ground plane as when the antenna will be used.
Also the outer shield of your test cable may form part of the antenna
and
this will affect the measurements.

At these GHz frequencies you will have better results if you tune the
antenna for resonance at the desired frequency instead of building a
matching network. The reason I say this is that VSWR and Return Loss
will
only change slightly if your reference plane is not right on but the
impedance will be off a fair amount. The reason is that the magnitude of
the reflection coefficient stays the same and only the phase angle
changes
if the cable is slightly long or short. However the phase angle rotation
results in a different impedance calculation. Even if you get a
reasonable estimate of impedance you then have the issue of designing
with
components and PCB design at Bluetooth frequencies.

Roger









--
*Dave - W?LEV*
*Just Let Darwin Work*


--
Dave - W?LEV
Re: At which point do we take the value of impedance to tune an antenna?

 

And please remember resonance is not necessarily at 1:1 SWR. It may or may
not be. Resonance is *defined* by (consult the complex portion of the
measured impedance): +jX = -jX. The resistance term is purely resistive
(consisting "mostly" of the radiation resistance) while the reactive
component is strictly reactive: capacitive or inductive.

Dave - W?LEV

On Mon, Aug 1, 2022 at 10:01 AM Diane BONKOUNGOU <dianebonk2@...>
wrote:

Hello Roger,
Thanks for reminding me, I will post on the other topic how I went about
correcting the electronic delay introduced by the SMA cable. My cable was
too long to correct the electronic delay at its end after doing the
calibration at the NanoVNA end that's why I had a lot of circles in the
Smith chart. I cut the cable further and have a quarter circle in the Smith
chart and then use the Edealy parameter in the NanoVNA to correct.
Best regards

Le ven. 22 juil. 2022 ¨¤ 17:03, Roger Need via groups.io <sailtamarack=
[email protected]> a ¨¦crit :

On Fri, Jul 22, 2022 at 04:34 AM, Diane BONKOUNGOU wrote:


Hello,
Hi, I am a beginner in antenna design and tuning.
I want my antenna to have a resonant frequency of 2.45GHz for
low-energy
Bluetooth communication.
And I want to know what to consider for the matching process.
I have made some measurements with Nanovna of my antenna. I have a
resonance
frequency of 2.28GHz and at this frequency, I have an impedance of
47.8-7.06j.
Can I take the value of this impedance at this frequency for the
matching
process or do I have to take the value of impedance at 2.45GHz?
Where to take the value of impedance for tuning?
Thanks.
You never posted in the other topic what you finally did to correctly
measure the antenna with the NanoVNA. If you don't establish the
"reference plane" rightat the antenna your impedance measurements will be
way off and you won't be able to design a matching network. Even if you
get a decent "reference plane" the antenna must be measured in circuit so
that you have a the same ground plane as when the antenna will be used.
Also the outer shield of your test cable may form part of the antenna
and
this will affect the measurements.

At these GHz frequencies you will have better results if you tune the
antenna for resonance at the desired frequency instead of building a
matching network. The reason I say this is that VSWR and Return Loss
will
only change slightly if your reference plane is not right on but the
impedance will be off a fair amount. The reason is that the magnitude of
the reflection coefficient stays the same and only the phase angle
changes
if the cable is slightly long or short. However the phase angle rotation
results in a different impedance calculation. Even if you get a
reasonable estimate of impedance you then have the issue of designing
with
components and PCB design at Bluetooth frequencies.

Roger









--
*Dave - W?LEV*
*Just Let Darwin Work*


--
Dave - W?LEV
Re: nanovna-saver : Sweep setting

F1AMM
 

In my Excel file, it is not about calibration but about measurements. The calibration has been done and has been corrected
/g/nanovna-users/message/29103

The calibration file shows values that follow each other in a sinusoidal fashion; we can therefore attempt an interpolation. For real measurement files, the curves are more difficult to modify by interpolation.

In any case, I perceived the difficulty of filtering measurements; it is not a very simple matter.

It is indeed a nanoVNA-F that I use and almost never without nanovna-saver because, on the screen of the box, I see nothing except to take the measurements at night.
--
F1AMM (Fran?ois)

-----Message d'origine-----
De la part de Arie Kleingeld > PA3A
mardi 2 ao?t 2022 10:12
Re: nanovna-saver : Sweep setting

 

I seldom calibrate the VNA with nanosaver, so really cannot tell how that one works out for me.
Nor is my VNA (Now a H4.3) the same as F1AMM's. So I cannot compare. (I read somewhere that Fran?ois uses an 'F'?)

An idea: Could there be a fault in the communication between the nano and the pc? Some of the calibration value's of F1AMM's excel file are way off, and some 'faulty' values occur several times.

Arie PA3A
Re: nanovna-saver : Sweep setting

F1AMM
 

Hello

Here is the test I did

Measurements on a loop antenna at a distance of 50 m (zero reagent around 7.100 MHz) between 1 and 20 MHz (1010 steps or 10 segments) made with a nanaoVNA-F and nanovna-saver. In order to access what is closest, it seems to me, to raw measurements, I did not put "filtering", I put 1/0.

I launched the measurement 5 times and I saved in .s1p each packet of 1010 measurements. It is therefore a total of 5050 elementary measurements.
You will find in Attachment a summary of the 5 groups of identifiable errors. Values ??are rounded for ease of reading. It doesn't matter what method to find these errors; there are at least those there but there may be others not identified.

Sheet: "Synth¨¨se"
Column a: reference number
Column b: frequency
Column c ¨C g: measurement of real S11
Column i ¨C m: measure of imaginary S11

The columns are to be paired; example: c2 and i2 are the a+jb of the same measure. Values ??assumed to be in error are highlighted in yellow

To analyse
No 1, 2, 5: a single false measurement (simple case)
No 3: two wrong measurements
No 4: the most curious? Why this ?

Try to imagine a method to identify these errors and, above all, to correct them. A solution may be to delete these error lines. We see the risk of involving an average value because it is not measurement noise.

In the sheet: "Ligne 4" one can examine the exact values. It is very disturbing that the two pairs of value measure n¡ã1 and measure n¡ã2 are strictly identical; for me, it hides something.

To your meditation
73
--
Fran?ois

³§²â²Ô³Ù³ó¨¨²õ±ð.³æ±ô²õ³æ
³§²â²Ô³Ù³ó¨¨²õ±ð.³æ±ô²õ³æ

Re: Correction of error introduce by a transmission line connect to the VNA port 1

 

why not just calibrate at the cable end??

much easier as messing with the long delay ... not?!?

dg9bfc sigi

ps did you check open and short (with cable!!)?!?!?

Am 01.08.2022 um 14:40 schrieb Diane BONKOUNGOU:

Hello,
Thanks, everyone for your tips.
Finally, this is what I've done.
Best regards

Le jeu. 21 juil. 2022 ¨¤ 00:44, Stan Dye <standye@...> a ¨¦crit :

Rather than cutting the cable, you should calibrate with the cable attached
to the nanovna, attaching the calibration standards at the other end of the
cable, using connector adapters if necessary. This way ensures that all
aspects of the cable (length, loss, etc.) are compensated for by the
calibration, perfectly removing all those circles from the smith chart.
Stan

On Wed, Jul 20, 2022, 2:18 PM Diane BONKOUNGOU <dianebonk2@...>
wrote:

Hello Siegfried,
Thanks for your response.
So If I cut more of my cable could I reduce the number of circles (the
phase shift)?. I struggle to correct the delay with a lot of circles.
Best regards.

Le ven. 15 juil. 2022 ¨¤ 15:35, Siegfried Jackstien <
siegfried.jackstien@...> a ¨¦crit :

You have to calibrate at the cable end with open short load
And with such big cable soldered to such a tiny pcb your results will
be
at least questionable...
On so high frequencies even an sma to n adaptor will shift your smith
90
degrees around... A long cable if not calibrated out will show a
handfull
of circles (as you can see)..
Dg9bfc sigi

Am 15.07.2022 14:20 schrieb dianebonk2@...:



Hello everyone,
I am a beginner in using the NanoVNA, I have a calibration problem
after
connecting a transmission line into the VNA. You can see some
pictures
of
the result in the attached document after connecting the cable to the
VNA
in the attached file.
Could someone tell me how to correct the impedance shift introduced
by
the
cable? Thanks
I went to the "electrical delay" menu to correct the problem by
adding
a
delay but it got worse. I don't know what to do.

I want to solder the cable afterwards into a PCB where we have
antenna
traces.
Re: At which point do we take the value of impedance to tune an antenna?

 

On Mon, Aug 1, 2022 at 03:15 AM, Siegfried Jackstien wrote:


You should better calibrate at the cable end and NOT on the vna..
No circles anymore!! Nothing to compensate via edelay..
I only use edelay to compensate say an sma to n adaptor.. But not to
compensate a cable length
I agree with you. Using edelay to de-embed a coaxial cable is not a good idea if impedance measurements are the goal. The attenuation of the cable affects the measurement. Things get worse the higher the frequency as cable loss increases.

Roger
Re: Correction of error introduce by a transmission line connect to the VNA port 1

Diane BONKOUNGOU
 

Hello,
Thanks, everyone for your tips.
Finally, this is what I've done.
Best regards

Le jeu. 21 juil. 2022 ¨¤ 00:44, Stan Dye <standye@...> a ¨¦crit :

Rather than cutting the cable, you should calibrate with the cable attached
to the nanovna, attaching the calibration standards at the other end of the
cable, using connector adapters if necessary. This way ensures that all
aspects of the cable (length, loss, etc.) are compensated for by the
calibration, perfectly removing all those circles from the smith chart.
Stan

On Wed, Jul 20, 2022, 2:18 PM Diane BONKOUNGOU <dianebonk2@...>
wrote:

Hello Siegfried,
Thanks for your response.
So If I cut more of my cable could I reduce the number of circles (the
phase shift)?. I struggle to correct the delay with a lot of circles.
Best regards.

Le ven. 15 juil. 2022 ¨¤ 15:35, Siegfried Jackstien <
siegfried.jackstien@...> a ¨¦crit :

You have to calibrate at the cable end with open short load
And with such big cable soldered to such a tiny pcb your results will
be
at least questionable...
On so high frequencies even an sma to n adaptor will shift your smith
90
degrees around... A long cable if not calibrated out will show a
handfull
of circles (as you can see)..
Dg9bfc sigi

Am 15.07.2022 14:20 schrieb dianebonk2@...:




Hello everyone,
I am a beginner in using the NanoVNA, I have a calibration problem
after
connecting a transmission line into the VNA. You can see some
pictures
of
the result in the attached document after connecting the cable to the
VNA
in the attached file.
Could someone tell me how to correct the impedance shift introduced
by
the
cable? Thanks
I went to the "electrical delay" menu to correct the problem by
adding
a
delay but it got worse. I don't know what to do.

I want to solder the cable afterwards into a PCB where we have
antenna
traces.



















E-delay correction.docx
E-delay correction.docx

Re: At which point do we take the value of impedance to tune an antenna?

Diane BONKOUNGOU
 

Hello,
Thanks for your reply.
I am using a quarter wavelength antenna.
Best regards

Le ven. 22 juil. 2022 ¨¤ 16:59, Jim Lux <jimlux@...> a ¨¦crit :

On 7/22/22 8:36 AM, Zack Widup wrote:
You should measure the impedance at the frequency you plan on using. I
have
found fairly large variations over a few MHz in this range before.

Zack W9SZ
Most simple antennas, near their design frequency, have an impedance
curve that looks a lot like a RLC resonance. The real part changes
fairly slowly, but the imaginary part changes quickly.


On the attached graph (impedance of a dipole), you can see that X
changes from about -40 to +40 going from 90 to 100% of a half wavelength
(resonance is at about 95% half wavelength), while R goes from 53 to 75
ohms over the same frequency range.

A 5% variation in frequency isn't huge (at 2.45 GHz, 5% is 120 MHz) - If
you think of the antenna as a filter, it's not even down 3dB at 5%.

Zmag is the absolute value of the Z.

So if you put a L or C in to "cancel" the reactive part,
Re: At which point do we take the value of impedance to tune an antenna?

 

You should better calibrate at the cable end and NOT on the vna..
No circles anymore!! Nothing to compensate via edelay..
I only use edelay to compensate say an sma to n adaptor.. But not to compensate a cable length
Dg9bfc sigi

Am 01.08.2022 12:01 schrieb Diane BONKOUNGOU <dianebonk2@...>:




Hello Roger,
Thanks for reminding me, I will post on the other topic how I went about
correcting the electronic delay introduced by the SMA cable. My cable was
too long to correct the electronic delay at its end after doing the
calibration at the NanoVNA end that's why I had a lot of circles in the
Smith chart. I cut the cable further and have a quarter circle in the
Smith
chart and then use the Edealy parameter in the NanoVNA to correct.
Best regards

Le ven. 22 juil. 2022 ¨¤ 17:03, Roger Need via groups.io <sailtamarack=
[email protected]> a ¨¦crit :

On Fri, Jul 22, 2022 at 04:34 AM, Diane BONKOUNGOU wrote:


Hello,
Hi, I am a beginner in antenna design and tuning.
I want my antenna to have a resonant frequency of 2.45GHz for
low-energy
Bluetooth communication.
And I want to know what to consider for the matching process.
I have made some measurements with Nanovna of my antenna. I have a
resonance
frequency of 2.28GHz and at this frequency, I have an impedance of
47.8-7.06j.
? Can I take the value of this impedance at this frequency for the
matching
process or do I have to take the value of impedance at 2.45GHz?
Where to take the value of impedance for tuning?
Thanks.
You never posted in the other topic what you finally did to correctly
measure the antenna with the NanoVNA.? If you don't establish the
"reference plane" rightat the antenna your impedance measurements will
be
way off and you won't be able to design a matching network.?? Even if
you
get a decent "reference plane" the antenna must be measured in circuit
so
that you have a the same ground plane as when the antenna will be used.
? Also the outer shield of your test cable may form part of the antenna
and
this will affect the measurements.

At these GHz frequencies you will have better results if you tune the
antenna for resonance at the desired frequency instead of building a
matching network.?? The reason I say this is that VSWR and Return Loss
will
only change slightly if your reference plane is not right on but the
impedance will be off a fair amount. The reason is that the magnitude of
the reflection coefficient stays the same and only the phase angle
changes
if the cable is slightly long or short.? However the phase angle
rotation
results in a different impedance calculation.?? Even if you get? a
reasonable estimate of impedance you then have the issue of designing
with
components and PCB design at Bluetooth frequencies.

Roger
Re: At which point do we take the value of impedance to tune an antenna?

Diane BONKOUNGOU
 

Hello Roger,
Thanks for reminding me, I will post on the other topic how I went about
correcting the electronic delay introduced by the SMA cable. My cable was
too long to correct the electronic delay at its end after doing the
calibration at the NanoVNA end that's why I had a lot of circles in the
Smith chart. I cut the cable further and have a quarter circle in the Smith
chart and then use the Edealy parameter in the NanoVNA to correct.
Best regards

Le ven. 22 juil. 2022 ¨¤ 17:03, Roger Need via groups.io <sailtamarack=
[email protected]> a ¨¦crit :

On Fri, Jul 22, 2022 at 04:34 AM, Diane BONKOUNGOU wrote:


Hello,
Hi, I am a beginner in antenna design and tuning.
I want my antenna to have a resonant frequency of 2.45GHz for low-energy
Bluetooth communication.
And I want to know what to consider for the matching process.
I have made some measurements with Nanovna of my antenna. I have a
resonance
frequency of 2.28GHz and at this frequency, I have an impedance of
47.8-7.06j.
Can I take the value of this impedance at this frequency for the
matching
process or do I have to take the value of impedance at 2.45GHz?
Where to take the value of impedance for tuning?
Thanks.
You never posted in the other topic what you finally did to correctly
measure the antenna with the NanoVNA. If you don't establish the
"reference plane" rightat the antenna your impedance measurements will be
way off and you won't be able to design a matching network. Even if you
get a decent "reference plane" the antenna must be measured in circuit so
that you have a the same ground plane as when the antenna will be used.
Also the outer shield of your test cable may form part of the antenna and
this will affect the measurements.

At these GHz frequencies you will have better results if you tune the
antenna for resonance at the desired frequency instead of building a
matching network. The reason I say this is that VSWR and Return Loss will
only change slightly if your reference plane is not right on but the
impedance will be off a fair amount. The reason is that the magnitude of
the reflection coefficient stays the same and only the phase angle changes
if the cable is slightly long or short. However the phase angle rotation
results in a different impedance calculation. Even if you get a
reasonable estimate of impedance you then have the issue of designing with
components and PCB design at Bluetooth frequencies.

Roger
Re: nanovna-saver : Sweep setting

F1AMM
 

What if you slightly change the frequency range and/or number of segments?
Are the errors still at the same frequency?
** No, the "clicks" are never in the same place. We will say, to simplify, that it is parasites that cause this. We find the same thing in the .S1p files but it's less troublesome. If I want data without click, I do the same, I correct.
When we observe the curves on the screen of the box there are also clicks and there, impossible to correct them

I forgot to mention:

The sweep had been set to 25/6
nanaovna-saver version is 0.3.10-Win7
The box is NanoVNA-F v0.1.4

by
--
F1AMM (Fran?ois)

-----Message d'origine-----
De la part de Victor Reijs
samedi 30 juillet 2022 07:48
Re: nanovna-saver : Sweep setting

 

Hello Francois,

What if you slightly change the frequency range and/or number of segments?
Are the errors still at the same frequency?
Good work you are doing by trying to make it clear!

All the best,

Victor


Op za 30 jul. 2022 om 05:37 schreef F1AMM <18471@...>:

It would be helpful if you described the specific frequency span you are
using, the number of segments,
and the frequencies where the "errors" occur. If there is some sort of
bug in the software algorithm,
that would help to see where it originates.
** Hello
I am posting an example. The calibration file (.cal) corresponds to the
end of a 50 m coaxial cable (50 ¦¸). The frequency sweep range is 1 to 20
Mhz in 20 segments.

Follows the description of each sheet in the .xls file

.cal
---
Raw data from the .cal file converted through a .csv file

Garden 1-20 MHz 20 sec avg 25-6
-------------------------------------
Data from the .cal sheet

Algo
----
* Column A to G: the input data. It is "by hand" that I zoned in yellow
the cells identified as "in error".

* Column I to N: a first search for errors with formulas of the kind
=IF(ABS((D19+D21)/2-D20)>$J1;1;"")
In cell J1: the value of the maximum difference before being declared
abnormal. In my example 0.005 (0.5%) works fine

* Column P to U: precise identification of the cell in error by a formula
like
=IF(AND(K21=1;K20=1;K22=1);1;"")

* Column W to AB: correction of values ??coming from columns A to G with
formulas like
=IF(R13=1;(D12+D14)/2;D13)

* CSV-final
Corrected data formatting. The first three lines are special to take into
account that the algorithm does not know how to process the first three
lines of the original file
This sheet will be saved in .csv in order to produce the corrected .cal
but do not forget, beforehand, to save the workbook if you want to keep
track of the calculations. I added in this sheet the graph of one of the
shortR column to show that the evolution of the values of sinusoidal form

But it is also true that the nanoVNA hardware also has limitations and
boundaries,
and it is likely that the "error" points you are seeing in your
calibration is in fact a true
measurement, due to a condition in the hardware that happens at the
subject frequency. And so such an "error"

** It is very unlikely since in this case, it is a calibration file (.cal)
following the operation (closed, open load). I don't have access to the
built-in average function in nanaovna-saver. I'm just seeing the obvious
errors easily identify in the produced .cal file. The errors that my
algorithm locates are big errors that produce straight line segments in the
graphs with the worst effect. There may be other finer errors that I can't
locate.

--
F1AMM (Fran?ois)
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