开云体育

There's lots of different ways to plot the same data, and people develop their approaches based on the ones they're familiar with.
I guess, too, in the "bad old days" when plots were done by hand (or plotter) doing it all with one plot was more convenient.

Today, where you can flip among plots in the blink of an eye, yeah, a gain vs frequency plot would be useful. Your only question is "linear frequency scale or log".

Thanks for the illustration. How did you get Q = 145.8? Why does the rectangular plot needs phase slope added to discern? Is the dip it too broad and shallow? A rectangular phase plot is available. How would you use it?

Alan, if I handed you a device and asked you to find the series-resonant frequency and the bandwidth at that point with a NanoVNA, what would you do? If the VNA was equipped with the feature you're proposing, what would you do differently?

Brian

Here is an illustration... attached.

This is true for some measurements but not all...

Consider a one port measurement, only S11, for a shunt series resonator.

The jig is made using one section of the commercially available NanoVNA test board. Available on eBay, Amazon and from Chinese sellers. You can find discussions about this board on several posts in this group.

Alan, I don't understand what you're suggesting. If I wanted to find center frequency and Q, I'd just look at the rectangular plot, which is available.

Brian

Thank you.

A useful addition to your bag is a constant Q contour. The Q = 1
contour permits resonator unloaded Q to be determined from S11
or S21 data overlaid on the chart. Three dB bandwidth and center
frequency is is quick to view.

Hi Roger

Apologies for resurrecting an old post
I was just wondering if you could provide any details on the S11 / S21 test jig, it looks pretty much ideal for the matching tests I would like to try.
I am guessing that this is something you modified yourself & it's not available off the shelf ?
What are the origins of the base board ?

Thx
Brian

Nizar,
The renormalization makes some assumptions that may not apply to your balun, in particular that S11=S22.
This is often close to true for things like ceramic filters, but is probably not close for your balun.
--John Gord

More Smith chart tricks:



Brian

Hi Dave

as asked here below the attached new measurements with renormalized Z0 coax 78.5 Ohm and 50 Ohm ( first balun Zc= 62 Ohm) , cursor at the same frequency 14.125Mhz .

73's Nizar .

Hi Dave

Thanks
I do not use any external artifact to take S21 Losses measurements with equivalent 78.5 Ohm coax Z0 , i just use the DiSlord Z0 renormalisation option on Display menu, this option take on consideration all computing's needed to acte as a real 78.5 Ohm NanoVNA .

For measuring characteristic impedance of my Balun i use My owne purely experimental methode , no computing nor modeling just measuring the resistor value that focused the Smith diagram on one dote (resistor trimmer termination) and read the renormalized impedance value that make it exactly on the center of the the shart, it's easy methode, reliable and accurate enougth without any computing errors and estimation, only direct experimental measurement , see screenshoot illustration.

73's Nizar

According to the Github page it is the latest "Official" release, Feb 24 2025 . I just d/l it last week.
Don't know about older units. I have a Deepelec V3 and seems to be fine

Instead of reading where the plot intersects, read the numbers at the top
of the screen which is where your cursor is placed. You have:

-0.774 dB loss at 54.6 + j 35.2 ohms equivalent of 64 ohms for the
total impedance
-0 440 dB loss at 80.7 + j 24.8 ohms equivalent of 84 ohms for the
total impedance

The total impedance is derived by calculating the SQRT of the SUM of the
SQUARES.

Note that using the reflection measurement option as illustrated in the
first image, the total loss is 0.5 of the measured value as the RF must
pass twice through the network. The ratios above don't change.

So the loss at nominally 54 ohms real is 0.167 dB greater at 81 ohms real.

Also note that due to the non 50-ohm or non 72-ohm Zo of the transmission
line transformer (common mode choke), the Zo of the choke will transform
either resistance to something else between 50 and 80-ohms.

What you are using for your 50 and 72 ohm non-reactive loads for the load
in your common mode choke - the disc in the first picture?

How did you measure the impedance of our common mode choke? I usually take
two measurements to determine this:

1) Measure the capacitance with the far end of the choke open terminated.
This will give you the capacitance of the windings (pretty close).

2) Measure the inductance with the far end of the choke short terminated.
this will give you the inductance of the windings (pretty close).

Measure both of these using the Smith Chart and the cursor.

Then calculate the characteristic impedance of the transmission line choke
(common mode choke) using the following:

Zo = SQRT [Measured Inductance in Henries / Measured Capacitance in Farads]

NOTE: 1 ?H = 1E-6 H and 1 pF = 1E-12 F

Dave - W?LEV



both the

On Sun, May 11, 2025 at 6:03?PM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi All

i tryed to change the balun designe with the same FT140-43 but with 1X12
turns this time , I measure the charateristic impedance of the balun is
around 142 Ohm ( see Smith shart focused on the graph center) , but this
time with 78.5 Ohm renormalized coax impedance it gives the half with 50
Ohm normal coax , huge diffrence around 1db at 30Mhz , in add this new
balun seems have much more losses -2.5 db compared to the first one
-0.2db , why ?? what is not correct with this second balun , see
illustration below .
73's Nizar .

--

*Dave - W?LEV*


--
Dave - W?LEV

Hi All

i tryed to change the balun designe with the same FT140-43 but with 1X12 turns this time , I measure the charateristic impedance of the balun is around 142 Ohm ( see Smith shart focused on the graph center) , but this time with 78.5 Ohm renormalized coax impedance it gives the half with 50 Ohm normal coax , huge diffrence around 1db at 30Mhz , in add this new balun seems have much more losses -2.5 db compared to the first one -0.2db , why ?? what is not correct with this second balun , see illustration below .
73's Nizar .

Hi Dave
Thanks
Pse take a look to the graphic curve , the losses difference is huge over all the band from 50Khz to 30Mhz , marker value not so important here .
73's Nizar

Please compare at the same frequency. Your 50-ohm (actually 52-ohm)
measurement is at 27.7 MHz. Your 72-ohm measurement is at 14.2 MHz.
Please repeat at the same frequency and get back with us.

Dave - W?LEV

On Sun, May 11, 2025 at 4:47?PM Team-SIM SIM-Mode via groups.io <sim31_team=
[email protected]> wrote:

Hi

I am a little confused, my 1/1 balun done with FT140-43 2x10 turns with
1mm wire as illustrated by photo attached, i want to measure losses by S21
Logmag function after a good thru calibration, with renormalizing the coax
Zc impedance from 50 Ohm to 78.5 Ohm it gives me the double of losses with
78.5 Ohm coax compared to 50 Ohm coax Z, i can not explaine this ? why ?
see S21 responses attached , knowing that i measured the caracteristic
impedance of the balun it is around 62 Ohm as showen by graphic attached
here , any help ?

H4 + 1.2.40
73's Nizar

--

*Dave - W?LEV*


--
Dave - W?LEV

Hi

I am a little confused, my 1/1 balun done with FT140-43 2x10 turns with 1mm wire as illustrated by photo attached, i want to measure losses by S21 Logmag function after a good thru calibration, with renormalizing the coax Zc impedance from 50 Ohm to 78.5 Ohm it gives me the double of losses with 78.5 Ohm coax compared to 50 Ohm coax Z, i can not explaine this ? why ? see S21 responses attached , knowing that i measured the caracteristic impedance of the balun it is around 62 Ohm as showen by graphic attached here , any help ?

H4 + 1.2.40
73's Nizar

Hi
here my best adjustement to the balun around FT140_43, Zc = 62 Ohm , (SWR=1.25:1 with 78 ohm coaxial cable) .
the impedance is centered to the Smith shart and focused there with a resistance trimer for all HF band from 50kHz to 30Mhz..

73's Nizar