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No relay to switch the source to the second port.
(and no bridge on the second port, either)
The NanoVNA doesn't use a directional coupler - it's a straight up bridge on Ch0 and a pad on Ch1.

Now that you mention it, that would have been a fairly easy thing (but hard to fit in the original 2x3" size)

You can, in fact, use two NanoVNAs with SMA T connectors to do a full 4 parameter measurement without having to move cables. You can "almost" do it simultaneously, even. If NanoVNA B sees the sweep from NanoVNA A, (or vice versa) you get a momentary spike in the displayed data.
I tried it using NanoVNA-Saver (running two separate instances) and it calibrates nicely, etc.

Brian,

Ahh yes, the old HP AppCAD program. I loved that thing back in the day. Not perfect, but a pretty decent tool, and you can't beat the price. For those looking for more information on this program, and I recomend it highly for those wanting a useful tool, try starting at the following website for older versions, as well as related help files and information:



Good call, Brian, I hadn't used that in a while, because I'm currently teaching space engineering courses, but a useful program for anyone working with microwave circuits, filters, baluns etc.

Randy

Randy J. Jost, PhD
r.jost@...
435-770-9855 (c)

On Mon, Apr 28, 2025 at 08:22 AM, RANDY JOST wrote:

Really looking forward to your updated program to show students in my EM
courses how it should be done.

Randy, if the program proves helpful for your students, that would be just great.

I didn't set out to write an s-parameter plotter. I wrote a little utility to renormalize the s-parameter reference impedance. This lets you use a VNA to measure a filter whose termination impedances differ from 50 ohms without building a matching network. When it came time to test the program, I looked around for an s-parameter plotter. The only ones I could find either did not handle all s-parameters, had bugs, or were very awkward to use. So I wrote my own. While I was at it, I built renormalization into it.

If you need an s-parameter plotter oriented toward amplifiers for your students, try AppCAD:



It hasn't been updated since 2012, but it has many features for amplifiers I found nowhere else. I think this is the program that took me 45 minute to see a plot! This also may be the one with points slightly off in a group delay plot. Nevertheless, I think students might find it helpful.

Brian

Computer Results: Remember maybe four or five decades ago (man, its been
that long!) when all the computer "Yagi Design" applications hit hams with
stars in the eyes? Some were good, some were mediocre, some yielded
unreasonable results, and some were just off the wall. The "math" or
models behind them was fixed and allowed little, if any, real input from
the user other than frequency and number of elements. The general belief
was almost universal: "I designed it on my computer so it must be right and
better than any other option!" Wrong....... But hams almost "worshipped"
the results totally believing the computer could and did offer far better
results than any other method under the sun and blue sky.

At present, I would venture an hypothesis that we're in a similar situation
with the tried-and-true Smith Charts vs. the computer generated reams and
columns of computer generated numerals. Take your pick. I'm an old
fuddy-duddy fossil, and I'll stick with what is so clear and designed for
impedance space: The Smith Chart.

Yes, I use SimSmith extensively, but it's still the tool that was designed
specifically for impedance space, the venerable and highly useful Smith
Chart.

Would you say the computer, PC is better at the following?

Time Domain: The oscilloscope ... not a PC
Frequency Domain: The spectrum analyzer ... not a PC
Impedance Domain: The Smith Chart ... That's what this thread is all
about
Temperature Domain: The thermometer ... not a PC
Color Domain: The optical spectrometer (similar to the spectrum
analyzer) ... not a PC
Voltage Domain: The volt meter or DMM ... not a PC
Current Domain: The ammeter ... not a PC
Power Domain: The proper power meter ... not a PC
....
.....
......
.......

Fill in your favorite "space".

Dave - W?LEV

On Mon, Apr 28, 2025 at 3:07?AM William Heller via groups.io <wheller34052=
[email protected]> wrote:

While in colledge I took a computational physics class and was assigned a
matrix with fractions such 1/3, 1/7 to evaluate three ways by long hand
pencil and paper, with a handheld calculator, and writing a fortran
program. The calculator gave fairly consistent results among the students
while the computer results varied between plus and minus infinity. What a
clear leason that was.

On Sun, Apr 27, 2025, 7:14 PM Maynard Wright, P. E., W6PAP via groups.io
<ma.wright@...> wrote:

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 4/27/25 14:45, W0LEV via groups.io 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

Hi, Brian,

This looks really good to me. Very crisp and sharp lines. Using Gwenview under Kubuntu here in case it matters.

73,

Maynard
W6PAP

Hi,

home made antenna is with ONE sma connector (no balun added) while factory made has a wilkinson splitter and two cablesz

have I ever mentioned that to be a difference ? yes, one has SMA, the other has solder joints. Both have had the same balun (obviously)

factory antenna has a triangle "groundplane" (while homemade has not) ... so yes you may see high difference cause they are not as identical as you think

what triangles and what "groundplane" would those be ?

sidenote: it looks way roo small for 300mhz ... are you sure its not for 3 ghz?!? ;-)

pretty sure ;-)

Thanks

Wow, I love spirograph art, so cool! :-) Really looking forward to your updated program to show students in my EM courses how it should be done. Using a Smith Chart program along with the equations really helps to remove the black box / black magic aspect of so many aspects of antenna, transmission line and microwave engineering. At least for we old timers, I guess.

Randy J. Jost, PhD
r.jost@...
435-770-9855 (c)

Thanks, Dean. The S22 Smith plot is available. I've attached one that looks like abstract art. I was just curious whether I was gilding the lily.

The program includes a utility to merge two .s2p files containing S11 and S21 to produce a file with all four s-parameters. This is for NanoVNA users willing to take the trouble to measure both forward and reverse response. Both reference impedance renormalization and the Y21 method work best with all four parameters.

The 800 x 600 test plot looks fine. I think the forum rescaled the 1024 x 768 and then scaled it back to its original size.

I'm going to leave admittance for another day (probably tomorrow). I keep finding small bugs so I'm going to concentrate on digging them out before posting the program later today.

Brian

Brian,
S22 is also useful and a Smith chart presentation would be desirable. But this would have less priority because the nanovna does not have the capability to measure it. Plus, you can always measure s22 by reversing your ports and measuring S11.
I dont know if the nanovna lacks the second directional coupler or the chipset has this limitation, but you can work around, for $70!

73,
Dean W8ZF

This is just a test plot. I noticed that the 1024 x 768 plots I posted earlier were not exactly reproduced. They are slightly fuzzy and colors are a bit off. Let's see how well this this 800 x 600 plot does.

Brian

Well, I'm getting there. So many pesky details.

I find Smith plots fascinating. It's hard to resist the urge to post dozens of really strange and interesting curves. I hope I don't become an insufferable Smith plot zealot!

I think the value of Smith plots for me will be much more in the realm of instant pattern recognition than analytical.

I've provided for S22 Smith plots as well as S11. Does anyone use them for S22?

Brian

home made antenna is with ONE sma connector (no balun added) while factory made has a wilkinson splitter and two cablesz

factory antenna has a triangle "groundplane" (while homemade has not) ... so yes you may see high difference cause they are not as identical as you think

dg9bfc sigi

sidenote: it looks way roo small for 300mhz ... are you sure its not for 3 ghz?!? ;-)

Am 28.04.2025 um 10:58 schrieb kellogs via groups.io:

Hello,

Homemade BLUE bowtie antenna vs factory made BLACK whole board with the same bowtie antenna.

Over 300 - 330 MHz range I am seeing some ~20 change in reactance with the home made antenna and ~50 ohm with the factory made. Also the resistance is 7-8 times greater for the factory made antenna, also varying much more.

Sames:
- placement of the antenna
- calibration place, cables and others related (*)

Diffs:
- calibration range: 300-330 for home made vs. 235-395 for factory made
- (*) connection to home made antenna through SMA connectors vs. direct soldering for the factory made antenna;
- calibrated with standards for home made vs. with wire / nothing / two 100 ohm resistors measured at 50.5 ohms with DMM

Is it normal to see such large measurement differences ?

Thank you

Is the Nanovna connected?
Nanovna-app doesn't sweep until you press the start sweep button, did you do that?

I downloaded the Nano VNA App from the website. And tonight I tried to use it unsuccessfully. I had connected the vna to my laptop > selected com port 1 for the usb, and didn't get a response indicating a sweep after going through the steps for calibration.
I have a full wave 40m to 10m skywire loop that I use.
I'm just wondering what I may have missed during the setup to the laptop. I have a presentation to do very soon and I hope to demonstrate it.
DE KD5SMF, MARK

While in colledge I took a computational physics class and was assigned a
matrix with fractions such 1/3, 1/7 to evaluate three ways by long hand
pencil and paper, with a handheld calculator, and writing a fortran
program. The calculator gave fairly consistent results among the students
while the computer results varied between plus and minus infinity. What a
clear leason that was.

On Sun, Apr 27, 2025, 7:14 PM Maynard Wright, P. E., W6PAP via groups.io
<ma.wright@...> wrote:

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 4/27/25 14:45, W0LEV via groups.io 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

From an educational aspect it would be useful to have the option of displaying gamma - maybe a separate selection option to display either SWR and frequency or impedance and gamma?
Dave, ZL3FJ

When you calibrate the Nano (on device calibration) in the range as the
documentation
suggests 0-900MHz with 401 points and then calibrate using the NanoVNA
Saver in the same
range using, for example, 2000 points the Saver will get the interpolated
results from the
device, not raw values. Same goes if you change the range. This, obviously,
leads to errors.
Remove the calibration and save that to the default slot (0 slot) when
using NanoVNA Saver.

On Sat, 26 Apr 2025 at 19:39, Dean W8ZF via groups.io <dwfred=
[email protected]> wrote:

Thanks Dave,
So if the H4 internal cal is *independent* of the nanovna-saver cal,
exactly what are you clearing with nanovna-saver's "clear all cals"and when
would that be necessary?
I ALWAYS either calibrate prior to measurements (and upon any sweep range
or source power change) or I alternatively load a saved calibration file
generated by nanovna-saver. Doesn't using the calibration assistant or
loading the cal file "clear all cals"?

I understand the principles and use of a VNA. I'm a Senior Principal RF
engineer and have used professional VNAs for 45 years. But I am new to
the nanovna VNA implementation and the interactions of the H4 with software
interfaces. What would be the source of information on whether
nanovna-saver uses raw data from the nanovna as part of its calibration,
nor not? I can always use the internal calibrate routine in the H4 for
mobile use, it looks like that's necessary (since the nanovna-saver cal
data is independent). But I am still not convinced that I can trust
nanovna-saver's calibration (because MAYBE it depends on the H4's cal
state).

Thanks and 73,
Dean W8ZF

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