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On Thu, May 15, 2025 at 11:44 AM, W0LEV wrote:

Please let us know where you are going with this

Dave, I think Alan is pointing out that I'm using port 1 data for a component measured between the two ports. True, but I'm just using the data to exercise my program, not to draw conclusions about the part.

As long as we're chasing anomalies, here's a good one. It's an MA magnitude/angle file where the VNA botched a point near 180 deg. I'm guessing it was attempting some sort of averaging and wound up with an angle of -1.3 deg when it should be near 180 (or -180). The bad point is in the middle of the data listing.

Brian

Please let us know where you are going with this:

QUOTE: s11 measure in series mode between the channels.

S11 and S22 are reflection measurements.

Dave - W?LEV

On Thu, May 15, 2025 at 6:17?PM alan victor via groups.io <avictor73=
[email protected]> wrote:

s11 measure in series mode between the channels.

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*Dave - W?LEV*


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Dave - W?LEV

Hi Roger

Thanks , I re do the measure of my 25m of RG213 at 100Mhz (Span 5Mhz ) by this cicle methode see illustration below with graphical renormalized Z0 to center impedances circle around center smith shart.
73's Nizar

On Thu, May 15, 2025 at 11:17 AM, alan victor wrote:

s11 measure in series mode between the channels.

Does this explain the trace gap? I assume that's what you're referring to.

Brian

s11 measure in series mode between the channels.

Those interested in more detail on my last post will find this article informative. The graphs at the end show what should be expected when making measurements of characteristic impedance of coaxial cables.

Nizar,
What I pointed out in my previous post is that your characteristic impedance measurements were not in accordance with well defined transmission theory.

Your results showed a rise in characteristic impedance and then considerable rolloff especially near 100 MHz. What should be observed is a slow decrease which flattens out at VHF. This can be seen in the graphic I posted.

After a few MHz the equation is Zc = SQRT (L/C) where L and C are the inductance and capacitance per unit length respectively. C can be considered constant with frequency while L decreases with frequency. L consists of internal and external inductance. The skin effect and the fact that internal inductance of the inner conductor decrease to zero at high frequencies are the prime reasons for this.

Yes, they can be pretty good for testing at HF if properly chosen and
measured. That's exactly what I do to "quailfy" potentiometers for use at
HF frequencies. It works!

Dave - W?LEV

On Thu, May 15, 2025 at 4:48?PM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi Dave

To be Honest , this is graphical results of my used potentiometre
illustrated with NanoVNA attached screenshoots : +j3 Ohm max at 30Mhz

73's Nizar .

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*Dave - W?LEV*


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Dave - W?LEV

Hi Dave

To be Honest , this is graphical results of my used potentiometre illustrated with NanoVNA attached screenshoots : +j3 Ohm max at 30Mhz

73's Nizar .

Any potentiometer used in the process can easily be verified to be
non-inductive using the VNA. That's how I choose the proper potentiometer.

Dave - W?LEV

On Thu, May 15, 2025 at 4:34?AM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi Roger

Thanks, its not assumed that test terminaison resistor should be a pure
real resistive value nor an accurate Zc muched impedance but just to be
approximatly reduced to a relatively focused and small circle of
impedances , what we measure in final is the circle center graphically
value with help of graphical renormalisation option added by DiSlord
without using Marker or cursur numerical displayed values over the desired
freq band , circle impedances has obviosly reactive impedances values but
turning graphically around the good center value to take on the end.

Hi Dave , Thanks , i have no offensive to mathematical approches, just i
prefer that mathematical threads can be taken by firmware as possible ( as
Dislord try to do) to facilitate nanovna use simply graphically especially
on using magical circles of Smith plots .

73s Nizar

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*Dave - W?LEV*


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Dave - W?LEV

This is a s21 measure with DUT in series with the channels.
At DC low freq begins at 50 then goes anti resonant and above that
an array of parasitic responses.

Hi Dave

Here My graphical illustrations of :

1) a 50 Ohm resistor thru a 1/1 balun Zc = 62 Ohm : real & X values change just a bit cross the 30Mhz band.

2) Same 50 Ohm resistor thru a 1/1 balun Zc=142 Ohm: real & X values change a lot cross the 30Mhz band , we need to adjust again the antenna to have a good SWR over the bands .

Both have a 50 Ohm pure resistor at Low frequency's .

That what I mean by impédances changes with this below illustrated graphical data's , John have the good question , did we really need a mutched CRC impedance to the system ?
My hunble response : Yess it's prefered to have a muched CRC impedance , otherwise we may need to retouch the antenna dimensions to tune again the overall system .

73's Nizar .

Here are the images.

Brian

Here's another issue revealed by trace dots. The data is for a Johanson 390 nH inductor. Note the trace gap at about 7 o'clock. The frequency steps are uniformly 1 MHz so the gap is not due to a frequency jump. Something changed dramatically in the VNA as the frequency crossed 7500 MHz. I wonder which side of the gap is correct. Or is either? If the application was important, I would trust any part of this data.

I had looked at this file several times with a normal trace, as shown in the second image, and I never noticed the flat spot that shows up as a gap with dots.

Brian

Hi Roger

Thanks, its not assumed that test terminaison resistor should be a pure real resistive value nor an accurate Zc muched impedance but just to be approximatly reduced to a relatively focused and small circle of impedances , what we measure in final is the circle center graphically value with help of graphical renormalisation option added by DiSlord without using Marker or cursur numerical displayed values over the desired freq band , circle impedances has obviosly reactive impedances values but turning graphically around the good center value to take on the end.

Hi Dave , Thanks , i have no offensive to mathematical approches, just i prefer that mathematical threads can be taken by firmware as possible ( as Dislord try to do) to facilitate nanovna use simply graphically especially on using magical circles of Smith plots .

73s Nizar

Another suggestion: Make the chart so that the outer boundary circle is say 1.5:1 or 2:1. I have a chart that is either 1.5:1 or 2:1 somewhere in my clutter.

On Wed, May 14, 2025 at 06:50 AM, Team-SIM SIM-Mode wrote:

Here My message about RG213 coax measurements posted here on Avril 5 2025:

for My RG213 cable (25m length) loaded by a 50.3 Ohm resistor ,
I used the centered impedances circle methode on smith graph with the
renormalized Z0 impedance ( option added by DiSlord) for different ferquency's
band (span always fixed to 4 Mhz) :

2Mhz ---> Zc = 52.6 Ohm
3Mhz ---> Zc = 52.5 Ohm
7Mhz ---> Zc = 52.0 Ohm
14Mhz ---> Zc = 53.0 Ohm
18Mhz ---> Zc = 53.0 Ohm
21Mhz ---> Zc = 54.0 Ohm
24Mhz ---> Zc = 54.0 Ohm
29Mhz ---> Zc = 52.0 Ohm
50Mhz ---> Zc = 49.0 Ohm
100Mhz ---> Zc = 43.5 Ohm

Your measurements do not agree with the calculated values for typical RG213. The characteristic impedance of Belden coax is around 50.6 ohms at 1 MHz and slowly decreases to about 50 ohms at 100 MHz. You can see that in the attached graph which is based on the parameters for this type of cable. It decreases because the inductance is decreasing with frequency.

The problem with your test method is that you will not have a pure resistance at the end of the cable as the frequency is increased. Any resistor (including SMD) will have some series inductance and there will also be capacitance across the resistance. The reactance associated with these components will be small at low frequencies but will be considerable at your highest measured frequency of 100 MHz. This is particularly true if you try to use any kind of small adjustable potentiometer for your test.

The end result is that your measurements will not be correct because you don't have a pure resistance load to base your measurements on.

Only one of the methods I presented involved a formula. What the dickens
is wrong with a little very simple algebra??

The other two methods are simple and only need a non-reactive
potentiometer, a VNA, or a DMM.

Why have you taken offense to my offering?

Dave - W?LEV

On Wed, May 14, 2025 at 10:58?PM Team-SIM SIM-Mode via groups.io
<sim31_team@...> wrote:

Hi Dave

I believe that everything I have presented here has already been
demonstrated both experimentally and graphically, without relying on
formulas or theoretical estimations. Nevertheless, approximation methods
are always possible, depending on the required level of accuracy."
73s Nizar

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*Dave - W?LEV*


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Dave - W?LEV

Hi Dave

I believe that everything I have presented here has already been demonstrated both experimentally and graphically, without relying on formulas or theoretical estimations. Nevertheless, approximation methods are always possible, depending on the required level of accuracy."
73s Nizar

QUOTE: In such a case, the measurements will be distorted by the
transformation introduced by the CRC's twin-lead line.

These CMCs are not made of just "twin lead line". They are intelligently
chosen conductors, ideally insulated with Teflon, and properly wound in
bifilar manner on an appropriate toroidal core.

Opinions don't count in this game of antennas and transmission lines! Real
properly measured data using the correct instruments and techniques are
what's important. In other words, "show me the data" !!!

Measure Z at the antenna. Any, and I do emphasize "any" reactance at that
point when coupled to a good 50-ohm XMSN line will alter the impedance at
the shack end of that line!!! The effect of a short length of transmission
line embodied in the CMC will do typically less than any reactive component
at the antenna. So, again, show me the data before offering "opinions".
Please.....

I'm only attempting to keep this thread on a technical basis and not based
on opinion. Science and engineering rely on hard theory and data to back
up the theories. Antenna and transmission lines rely on hard science and
data, not opinion.

Dave - W ?LEV

On Wed, May 14, 2025 at 9:36?PM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi Miro
I believe you asked the right question here.
In my opinion, not having the correct characteristic impedance (Zc) for
the CRC that matches the Coax/Antenna system slightly alters the impedance
seen by the coax from the antenna and also the propor resonnance frequency
, CRC become a part of resonnance frequency . It also affects the impedance
measurements taken at that point, especially if the NanoVNA is calibrated
right at the point just below the antenna. In such a case, the measurements
will be distorted by the transformation introduced by the CRC's twin-lead
line.

For example, consider a CRC with a Zc of 140 Ohms used with a 50 Ohm
coaxial system: the impedance measured with or without the CRC will be
different, and correcting the antenna accordingly becomes much more
difficult. On the other hand, if the CRC has a characteristic impedance
equal to that of the Coax/Antenna system, the measured impedance will be
the same before or after the CRC. This would greatly simplify both the
calculations and the practical adjustments needed to optimize the antenna
system.

73's Nizar

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*Dave - W?LEV*


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Dave - W?LEV