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The Smith chart, of course, can be replaced by any of many software packages that yield just numerical results, but not the feel for what's going on. One may be really happy with incorrect numbers that fall out of a computer or calculator where the Smith chart might make one think "That ain't right!"

I still use slide rules for pretty much the same reasons. Although I am thankful that I don't have to work my way manually through hyperbolic functions of complex argument as I did early in my career when no calculators or computers were readily available.

73,

Maynard
W6PAP

On Sun, Apr 27, 2025 at 04:31 PM, Dean W8ZF wrote:

With regards to the marker, I can offer an opinion. I rarely used the raw
reflection coefficient directly. I was looking to find a return loss, VSWR, or
impedance, all of which would require calculation from the reflection
coefficient and phase. A marker that did that calculation on the fly is very
useful, just as you are doing.

Good. The less clutter the better. So far I display frequency and SWR. Impedance is just about ready to test. I will have to add the upside-down ohms symbol to my homebrew fonts when I do admittance. I love that symbol. We'll see about return loss.

Thanks for being open to input!

Since I don't know what I'm doing, I welcome any help!

Testing the Smith chart on various .s2p files I've collected, mostly from SMD L and C vendors, I immediately noticed characteristic curves. I don't know what all the whorls and wiggles mean yet, but the Smith curves are much more distinctive than the rectangular versus-frequency plots I've been looking at for weeks.

Brian

Hi Brian,
With regards to the marker, I can offer an opinion. I rarely used the raw reflection coefficient directly. I was looking to find a return loss, VSWR, or impedance, all of which would require calculation from the reflection coefficient and phase. A marker that did that calculation on the fly is very useful, just as you are doing.
Thanks for being open to input!
73,
Dean W8ZF

Do you refer to Phillip Smith's original paper?

DaveD
KC0WJN


On Sun, Apr 27, 2025 at 17:45 W0LEV via groups.io <davearea51a=
[email protected]> wrote:

From the original publication in the early 1950s, the Smith Chart addressed
impedance space, not just line lengths.

I once had in my hands while working for a living (now retired) the
original publication which introduced the world to the Smith Chart. I
offered the engineer who owned it $200 on the spot. He refused. I upped
my offer to $300 on the spot. He again refused. He also refused my $400
offer. I gave up. At least I got to actually handle and leaf through it!

Now I have the time in retirement, but no $$ for "frivolous" things like
that.....

As an EMC/RFI/RF design engineer and spending a good amount of my
professional life as well as on the hobbies designing, building, and
matching antennas and any number of RF/?W circuits, the Smith Chart will go
to my grave with my decaying body......

Dave - W?LEV

On Sun, Apr 27, 2025 at 9:30?PM Team-SIM SIM-Mode via groups.io
<sim31_team=
[email protected]> wrote:

Hi
The Smith chart is simply a specific graphical method for illustrating
impedances—originally as a function of line length, and now, with the
NanoVNA, as a function of frequency. Its advantage lay in simplifying the
plotting process on paper using just a compass to draw the impedance

circle

based on the electrical length of the line, resulting in a neat circle
centered on the chart's origin. With the NanoVNA, this also produces a
clean circle around the center, but by varying the stimulus frequency.?

This method has allowed me to measure the characteristic impedance of
coaxial cables precisely and reliably at a given frequency by centering

the

impedance circle on the chart's origin. This is achieved by adjusting the
normalization impedance using the feature provided in DiSlord firmware
version 1.2.40.

No other graphical method offers such performance and ease for measuring
characteristic impedance (Zc) with this level of elegance and precision.

It

truly is the 'magic circle' of the Smith chart.?

73s Nizar

















ChatGPT peut faire des erreurs. Envisagez de vérifier les informations
importantes

--

*Dave - W?LEV*


--
Dave - W?LEV

On Sun, Apr 27, 2025 at 02:33 PM, Dean W8ZF wrote:

While you're at it, the option of an admittance version of the Smith chart
would be also helpful.

Another useful input, Dean. I had not planned to do admittance, but adding it should not be hard.

I've implemented a marker. You click near the curve to activate it. You can click again or rotate the mouse wheel to move it. I'm thinking of displaying frequency, SWR, and Z for the marker. Can I get away without displaying the reflection coefficient? I like to keep think as simple as possible.

Brian

From the original publication in the early 1950s, the Smith Chart addressed
impedance space, not just line lengths.

I once had in my hands while working for a living (now retired) the
original publication which introduced the world to the Smith Chart. I
offered the engineer who owned it $200 on the spot. He refused. I upped
my offer to $300 on the spot. He again refused. He also refused my $400
offer. I gave up. At least I got to actually handle and leaf through it!

Now I have the time in retirement, but no $$ for "frivolous" things like
that.....

As an EMC/RFI/RF design engineer and spending a good amount of my
professional life as well as on the hobbies designing, building, and
matching antennas and any number of RF/?W circuits, the Smith Chart will go
to my grave with my decaying body......

Dave - W?LEV

On Sun, Apr 27, 2025 at 9:30?PM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi
The Smith chart is simply a specific graphical method for illustrating
impedances—originally as a function of line length, and now, with the
NanoVNA, as a function of frequency. Its advantage lay in simplifying the
plotting process on paper using just a compass to draw the impedance circle
based on the electrical length of the line, resulting in a neat circle
centered on the chart's origin. With the NanoVNA, this also produces a
clean circle around the center, but by varying the stimulus frequency.?

This method has allowed me to measure the characteristic impedance of
coaxial cables precisely and reliably at a given frequency by centering the
impedance circle on the chart's origin. This is achieved by adjusting the
normalization impedance using the feature provided in DiSlord firmware
version 1.2.40.

No other graphical method offers such performance and ease for measuring
characteristic impedance (Zc) with this level of elegance and precision. It
truly is the 'magic circle' of the Smith chart.?

73s Nizar

















ChatGPT peut faire des erreurs. Envisagez de vérifier les informations
importantes

--

*Dave - W?LEV*


--
Dave - W?LEV

Brian,
While you're at it, the option of an admittance version of the Smith chart would be also helpful.
73,
Dean W8ZF

Hi
The Smith chart is simply a specific graphical method for illustrating impedances—originally as a function of line length, and now, with the NanoVNA, as a function of frequency. Its advantage lay in simplifying the plotting process on paper using just a compass to draw the impedance circle based on the electrical length of the line, resulting in a neat circle centered on the chart's origin. With the NanoVNA, this also produces a clean circle around the center, but by varying the stimulus frequency.?

This method has allowed me to measure the characteristic impedance of coaxial cables precisely and reliably at a given frequency by centering the impedance circle on the chart's origin. This is achieved by adjusting the normalization impedance using the feature provided in DiSlord firmware version 1.2.40.

No other graphical method offers such performance and ease for measuring characteristic impedance (Zc) with this level of elegance and precision. It truly is the 'magic circle' of the Smith chart.?

73s Nizar

















ChatGPT peut faire des erreurs. Envisagez de vérifier les informations importantes

Paul,
In your screenshot, the vertical grid line nearest the center is at 910.000 MHz, the nearest "round" number.
Does that explain the offset you see?
--John Gord

Yes, Dean points out an interesting aspect - if you look at it and it’s just spirals, you know a simple network is likely to work. If it’s back and forth zig zagging, probably not.

On Sun, Apr 27, 2025 at 11:58 AM, alan victor wrote:

Your density is finer than it needs to be. Which is ok. However, might
consider the
one standard that is: 0 , 10, 25, 50, 100, 250, and infinity...

I appreciate the advice, Alan. Usually I only program features that I would use myself. I don't anticipate using the Smith chart and I have no experience with them so it's hard to know what detail is reasonable. I'll post a message when the program is available.

Thanks also to Dean for your input.

Brian

Your density is finer than it needs to be. Which is ok. However, might consider the
one standard that is: 0 , 10, 25, 50, 100, 250, and infinity...

Same on both reactive contours.

Hi Brian,
As an RF engineer, I depend on Smith charts for the intuitive understanding they enable. It is easy to look at at an impedance and instantly understand what would best match an impedance. It's easy to visualize what effects rotation through a transmission line would have, and pretty much how complicated a matching network will be, before ever designing it. It's invaluable, in my opinion. Just my 2 cents worth. Glad you found it easy to implement.

73,
Dean W8ZF

The marker will go to the nearest scan point. You have your H4 set for 101pts, you can set it to 401 for much finer resolution.

Question, why when I set a center frequency of 910.525 MHz on my Nano VNA-H4 (as I did here within this image) then I set a marker for 910.525MHz, they are offset from each other?

Well, it was easier to implement than I thought. And a lot more fun! I need to fine-tune the circles and then think about some sort of frequency annotation or readout.

Brian

On Sun, Apr 27, 2025 at 06:28 AM, Maynard Wright, P. E., W6PAP wrote:

I don't known whether or not I would have seen that solution without resort to
the visual presentation of a Smith chart.

Very interesting, Maynard. I had pretty much decided to skip implementing a Smith chart until I read your response. I'm all for facilitating insight.

I never worked in RF professionally. The Smith chart is foreign to me. Perhaps many NanoVNAs users favor it because it is familiar from their professional work. Offering something familiar may be another good reason to implement it.

Incidentally, I wrote my program mainly to plot all four s-parameters, provide reference impedance renormalization to allow measurement and optimization of filters without building a matching network, and to implement the Y21 series-through method that cancels stray reactance. I want to avoid unnecessary embellishments, but it sounds like a Smith chart might be useful.

Brian

Bob,

I have gone through that some time ago.
It is quite useful, though not exhaustive.

73
Jon, VU2JO

On Sun, Apr 27, 2025 at 7:12?PM Bob Ecclestone VK2ZRE via groups.io
<becclest@...> wrote:

Jon,
Log into the groups.io nanovna group and go to the Files section.
Look for the "Absolute Beginners Guide". I think V6.20 is the last update.
It does not cover all the bells and whistles of the latest firmware, but
it is a good basic intro to the NanoVNA and VNAs in general.
By the time you work through that, you will be well on your way.
There is also a reasonably up to date version of the Menu Tree document
in there too somewhere. It explains in detail what the various Menu
Items do.
Enjoy your fantastic new piece of test equipment.
HTH. Cheers...Bob VK2ZRE


On 27/04/2025 4:26 pm, Jon via groups.io wrote:

Thank you Dave.

On Sun, Apr 27, 2025 at 5:07?AM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

No, it does not. However, there are several publications out that

instruct

one on using the NANOVNAs. Once you learn the basics, that should map

over

to any VNA, professional or NANO.

Dave - W?LEV

On Sat, Apr 26, 2025 at 11:06?PM Jon via groups.io <vu2jo0=
[email protected]> wrote:

Dave,

Does the NanoVNA come with an instruction manual?

I received only a menu chart, and no other booklet.

73

Jon, VU2JO

On Sun, Apr 27, 2025 at 3:45?AM W0LEV via groups.io <davearea51a=
[email protected]> wrote:

Yes, if your SAVER is miles outside of your intended cal range, you

need

to

do a cal on the native device first. I've never had that problem, so

I

wouldn't know. I've used professional VNAs for decades on the job

(I'm

now

retired) and own an HP 8753C, so I really didn't have to even open the
instruction book. Please forgive me.......

Dave - W?LEV

On Sat, Apr 26, 2025 at 6:17?PM Stan Dye via groups.io <standye=
[email protected]> wrote:

On Sat, Apr 26, 2025 at 10:39 AM, Dean W8ZF wrote:

because MAYBE it depends on the H4's cal state

From the nanovna-saver github readme (
):
Quote:
Calibration

Before using NanoVNA-Saver, please ensure that the device itself is

in

a

reasonable calibration state.

A calibration of both ports across the entire frequency span, saved

to

save slot 0, is sufficient. If the NanoVNA is completely

uncalibrated,

its

readings may be outside the range accepted by the application.

-------------
And from the code itself, the following code fragment shows that
nanovna-saver uses the "scan" command, rather than the "scanraw"

command,

to get its data from nanovna. The "scan" command returns S11/S12

data

with nanovna internal calibration (if any) applied.

def setSweep(self, start, stop):
self.start = start
self.stop = stop
list(self.exec_command(f"scan {start} {stop}

{self.datapoints}"))

-------------

So nanovna-saver indeed does depend on the calibration state of the
nanovna; they are not independent.
Q.E.D.

If you want independent calibration, use nanovna-app instead. It is

a

quite different application with its own learning curve, but it has
specific settings to use the nanovna internal or nanovna-app

calibration.

I use both apps, they both have excellent features.

Stan KC7XE

--

*Dave - W?LEV*


--
Dave - W?LEV

--

*Dave - W?LEV*


--
Dave - W?LEV

Jon,
Log into the groups.io nanovna group and go to the Files section.
Look for the "Absolute Beginners Guide". I think V6.20 is the last update.
It does not cover all the bells and whistles of the latest firmware, but it is a good basic intro to the NanoVNA and VNAs in general.
By the time you work through that, you will be well on your way.
There is also a reasonably up to date version of the Menu Tree document in there too somewhere. It explains in detail what the various Menu Items do.
Enjoy your fantastic new piece of test equipment.
HTH. Cheers...Bob VK2ZRE

Jim,

You are exactly right about the graphical design of a matching network. Some years ago I worked up a network which involved solving a quadratic equation, easily done. So I had an analytic solution for that network.

I wanted a similar, but not identical network that also involved a quadratic. Well, sort of: the equation for that network involved a multiplicative term that made its solution difficult to visualize, at least for me.

But in plotting what I wanted each network to do on a Smith chart, I could see a reverse symmetry between the networks. Modifying the first solution using that information yielded an exact analytic solution for the second network.

I don't known whether or not I would have seen that solution without resort to the visual presentation of a Smith chart.

73,

Maynard
W6PAP