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I am trying to evaluate the performance of a 1:1 balun with 11 turns RG400 on 2XFT240-K torroids. What are the parameters I need to look at when using the NanoVNA, which would tell me that there is sufficient choking impedance at the frequency of operation? I believe I cannot read off the impedance Z directly even if I use NanoVNA Saver (V0.1.4). Appreciate any help as I am pretty new and learning to use a VNA.

BR-Nan

Hi Nan -

What are the parameters I need to look at when using the NanoVNA,
which would tell me that there is sufficient choking impedance
at the frequency of operation?

First, set STIMULUS for the range of interest before calibrating.
Then I would go here:
He has other, related, articles:

Our Wiki application notes include related "ferrite bead measurements:"
/g/nanovna-users/wiki/Application-Notes

.. and here is a blog with some related techniques and tips:

On Sun, Oct 27, 2019 at 10:26 AM, Nan wrote:

I am trying to evaluate the performance of a 1:1 balun with 11 turns RG400 on
2XFT240-K torroids.

It's not clear from your question what exactly you're trying to measure - balun or RF-choke. According to your description you're trying to measure RF-choke instead of balun.

You can measure RF-choke by connecting it's braid from two sides into CH0 and measure reactance.

If you want to measure balun, then this is different story.

Hi Oristo

Many thanks for your help. If I need to get S21 Mag(db) and S21 Phase (deg), can I use CH1 Logmag and CH1 Phase? Similarly if I need to measure S11Mag (db) and S11Phase(deg), do I use CH0 Logmag and Phase respectively? I cannot get S21 values on the graphical plot when I use NanoVNA Saver but can read off the values direct from the VNA display. Am I doing this right?

BR-Nan

Hi Nan-

I use NanoVNA Saver

Sorry, I use scripts to directly read nanoVNA S11 and S21 values by shell commands

I suggest that you search the current NanoVNA Saver topic
/g/nanovna-users/topic/nanovna_saver_0_1_3/34559684

or in all messages, e.g.
/g/nanovna-users/search?d=0&ev=false&q=saver+impedance

On Sun, Oct 27, 2019 at 08:26 AM, Nan wrote:

What are the parameters I need to look at when using the NanoVNA, which would
tell me that there is sufficient choking impedance at the frequency of
operation?

The figure you are primarily interested in is the S11 Resistive component when the two wire ends of the choke are connected across CH0.

You can also measure it as S21 by connecting the two wire ends between the center pin of CH0 and CH1 and then manipulate the data to give you the impedance.

However if you measure S21 insertion gain be aware that the value you are presented with is only valid in a 50 Ohms system, and the common mode impedance on the outside of a coax cable screen varies with wavelength and can be anything from a few tens of Ohms to several K Ohms.

So you can use the figures you obtain as guidance or for comparison purposes, but it won't tell the full story of how well (or badly) the choke will work in situ.

Type K material is similar to type 61 and is more suited to HF band applications. Type 52 may be a better choice for the majority of bands or type 43 or 31 for the LF bands.

Steve, G3TXQ's (SK), website will give you some guidance WRT what to expect with different windings and materials.



Regards,

Martin - G8JNJ

Hi Nan,

SimSmith can be used to predict figure of merit difference between 52 and 43 11T on 2X 240 cores. K is similar to 52. Attached is a plot. Little difference above 14MHz. 43 somewhat improved below 14MHz.

Additional information for using SimSmith:


John KN5L

Nan wrote: I am trying to evaluate the performance of a 1:1 balun with 11 turns RG400 on 2XFT240-K torroids.

Here's some AIM4170D results for 9 turns RG400 on 2xFT240-K toroids for comparison.

Here's the same 1:1 choke being measured on the NanoVNA.

Many thanks for the inputs. I am following G3TXQ method of measuring common mode impedance. I connected the shields of the input and outputs of the 1:1 Balun to CH0 and CH1 inputs of VNA. I am trying to get the S11 and S21 values to input into the XL calculator and I am confused about which readings I should take from the NanoVNA saver or directly from the NanoVNA. (I am using 2 X FT240-52 - not K, it was my typo error)

Can someone help me understanding this more clearly? Where I am stuck now is:

“ To get S21 Mag(db) and S21 Phase (deg), can I use CH1 Logmag and CH1 Phase? Similarly if I need to measure S11Mag (db) and S11Phase(deg), do I use CH0 Logmag and Phase respectively?” Can I get these values directly from the NanoVNA or do I need to use NanoVNA Saver or something else?

BR-Nan

I'll try to help, but mostly in order to understand: Why is it you need to
put something into the calculator? Can you not use the impedance
measurements which is shown in NanoVNA-Saver under "impedance" (for any
marker you place)?

S11 return loss is available, as is S11 phase, S21 phase, and S21 gain -
directly in NanoVNA-Saver. I believe these are all you need for the G3TXQ
calculator?

There really isn't any reason to have to go to a different piece of
software to do this: If someone can tell me how to do the calculations, I
might as well put them in the software, and make a "choke measuring mode"
or something :-)

--
Rune / 5Q5R

Hi Rune

If you go to G3TXQ's website: and click on the hyperlink "spreadsheet" which is almost at the bottom of the page , you will get a XL file which calculates "Z" from S11 & S21 data. Take note that the file was originally created in Open Document Format and needs to be converted to XL. I got some warning messages of possible format loss during conversion to XL 2016 so frankly I am not sure if my conversion process is correct & the formula's got corrupted. I also note that calculation of Z is based on S21 data only, and the formulas are as follows: (copied from the XL sheet and I am trying to understand this!)

R =100*10^(-S21mag/20)*COS(S21phase/57.29578)-100
X = -(R+100)*TAN(S21phase/57.29578)
Z = SQRT(R^2+X^2)

S21mag(dB) in NanoVNA Saver = |S21| - is this correct? OR is it Logarithmic Magnitude (Log Mag /dB Mag)
S21phase(deg) in NanoVNA Saver = S21 phase - this should be correct

Excellent software, its just me trying to learn to use it correctly! Any help is much appreciated.

BR-Nan

Nan wrote: I am following G3TXQ method of measuring common mode impedance.

Measuring the s21 of a choke is akin to measuring the s21 of a coil and to do that the coil needs to be terminated in its characteristic impedance. Steve and I had numerous email exchanges on that subject. If a coil or choke is not terminated in its characteristic impedance on Port2 of a VNA, one is measuring group delay, not signal delay. The VNA assumes a characteristic impedance of 50 ohms and Steve's following experiment proved that trying to measure s21 delay in a piece of 300 ohm twinlead produced "wildly varying s21 delays".

"Cecil, I just tried that simple experiment with 9.6ft of 300 Ohm ribbon I happened to have lying around. Simply connecting it directly between Port A and Port B of the analyser produced wildly varying S21 delays with a minimum of 3.4nSec at 13.5MHz I then roughly terminated the ribbon by inserting a 270 Ohm resistor between one leg and Port B, making 320 Ohms total. The reported S21 delay then varied only a little with frequency, typically being between 10nSec and 11 nSec. 73, Steve G3TXQ"

"I was inserting extra resistors Rt between the coil and Point B to change the coil termination. The one thing you can't get away from is that adding Rt makes a massive difference to the reported S21 delay even though it obviously can't add substantial physical delay."

Note: Rt is the extra resistance that Steve was putting in series at Port2 to try to approximate the characteristic impedance of the coil or choke.

Here's what Steve measured for your described 1:1 choke:

Nan wrote:

Take note that the file was originally created in Open Document Format and needs to be converted to XL

Or you COULD just go to the site, download the libreoffice suite, install it, open the file in open document format, and get on with things without kowtowing to or contributing money to the Microsoft Evil Empire in any way. It ain't perfect, but it's a good start.

Yeah, I'm one of those.

Monopolies, especially monopolies that provide shoddy crap which is NOT to standard or up to snuff for real end-user use, give me a major case of the pip. Add in built-in spy-ware and I'm really not going to go there.

I used to be Tier-3 manager for a univerity HELL desk for IT support (Yes, HELL. I lost the "P" the first week, it turned into another "L" almost immediately.) and relied for my paycheck on the fact that WinBLOWS (You prefer WinSUCKS?) was broken from the get-go. Nothing has gotten better in the latest iterations of the garbage provided from the Redmond Consortium. It's still "Not Ready For Prime Time." 340,000 viruses, trojans, and zero-day exploits can't all be wrong.....

Between BSD and Linux, and they're a LONG WAY from perfect, I can at least read the source and perhaps figure out and fix whatever idiocy is going on. (But systemd shouldn't be allowed to happen to any piece of poor, unsuspecting, hardware.)

--
Wes Will
N9KDY

Why?
The Microsoft Office suite has supported Open Document Format since 2007.

On 28 October 2019 at 00:06 N9KDY <n9kdy@...> wrote:


Nan wrote:

Take note that the file was originally created in Open Document Format and needs to be converted to XL

Or you COULD just go to the site, download
the libreoffice suite, install it, open the file in open document
format, and get on with things without kowtowing to or contributing
money to the Microsoft Evil Empire in any way. It ain't perfect, but
it's a good start.

Yeah, I'm one of those.

Monopolies, especially monopolies that provide shoddy crap which is NOT
to standard or up to snuff for real end-user use, give me a major case
of the pip. Add in built-in spy-ware and I'm really not going to go there.

I used to be Tier-3 manager for a univerity HELL desk for IT support
(Yes, HELL. I lost the "P" the first week, it turned into another "L"
almost immediately.) and relied for my paycheck on the fact that
WinBLOWS (You prefer WinSUCKS?) was broken from the get-go. Nothing has
gotten better in the latest iterations of the garbage provided from the
Redmond Consortium. It's still "Not Ready For Prime Time." 340,000
viruses, trojans, and zero-day exploits can't all be wrong.....

Between BSD and Linux, and they're a LONG WAY from perfect, I can at
least read the source and perhaps figure out and fix whatever idiocy is
going on. (But systemd shouldn't be allowed to happen to any piece of
poor, unsuspecting, hardware.)

--
Wes Will
N9KDY

Nigel A. Gunn, 1865 El Camino Drive, Xenia, OH 45385-1115, USA. tel +1 937 825 5032
Amateur Radio G8IFF W8IFF and GMRS WRBV701, e-mail nigel@... www

Hi Nan

VNA2180 that Steve used have 50 ohm impedance on both ports (A & B). So those formulas will work if vna ports of NanoVNA have 50 ohm impedance. But do they?

In post 1257: /g/nanovna-users/topic/32993803#1257
I calculated the output impedance of CH0 to be 51.53 ohms
and the input impedance of CH1 to be 53.85 ohms.

In the previous post of that thread, Alan got 51.27 ohms for CH0.
There's a bunch of assumptions being made in those calculations,
it would be interesting to measure these figures accurately.

The discussion about correction factors in post 1311
is continued in a different thread with post 1318

Jerry, KE7ER

These figures for the impedance of CH0, CH1 will vary considerably with frequency.

Jerry

I did measure both with another vna. Ch1 is indeed worse but I found both to be closer to 50 ohm. Currently traveling so don't access to the exact numbers
Next to the resistance difference ch1 has a relevant reactive component. Best to use a 10dB attenuator at ch1
Calibrate the thru with the 10dB to remove the calibration impact
--
NanoVNA Wiki: /g/nanovna-users/wiki/home
NanoVNA Files: /g/nanovna-users/files
Erik, PD0EK