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Its a fact, that inductance value, vary according to frequency.
How does the nanovna measure ?
Does it use the saved selected frequency range inside the nano ?

yes, I do have the female to female . I was to quick to assume I had something missing.
And, yes, I am following that Absolute Beginners manual . Some slight insignificant differences in software.

Hi Victor,

Interesting reading about cmc models and ways of establishing by measurements and maths of obtaining values for the various elements of the models form the links you provided, thanks.

Dominguez-Palacios et al (DP) paper uses S21 Voltage measurements, whilst the Hal document works on S11 impedance measurements. Fig 2(a) of DP paper is equivalent to HAL Fig 3 (a) – T0 connection, or as you describe in your notes CM0 as you find no appreciable difference to CM3.

For DM, the DP paper makes use of two baluns. The equivalent in the HAL document would be fig 3 (b) = T1 connection, an arrangement close to my original suggestion for measuring CMC DM, the differences being what started our excellent discussions and something yet to be ascertained is if there is any appreciable difference of techniques. For sure if one considers a CMC filter (extra capacitance on the far side), yes I fully agree that the techniques are not comparable.

Thus, I see that the ‘open’ measurement of the DP paper (fig 2 (c) is part of a series of tests of a particular method for the purposes of modelling, not an alternative to more conventional means of establishing performance of a cmc. Just as are the additional configurations of the HAL document Fig 3 (c), (d) & (e) with T4 being equivalent to DP paper ‘open’.

Interesting to note that in the HAL document, the conclusion is that results not only depend on components (tolerances?) but also on respective positioning (lay-out).This reminds me of a quotation I heard many years ago (can’t remember where/who it came from) =”Theoretically, practice and theory are the same, in practice, they are not!”

I have also been refreshing and improving my knowledge on transmission line transformers (TLT’s) and found for me a very useful reference = Ruthroff transmission line transformers, Guanella baluns, lowpass and bandpass filters, and balanced transmission lines using multilayer technology, Riaz R Sobrany, M.Eng.



Although aimed at microwaves and MICC type technology, chapter 3 covers basic theoretical operation of various Ruthroff TLT’s and chapter 4 Guanella types. Of interest to me in particular is his notes on testing baluns(on page 136 of pdf).

“Connecting two identical baluns with unknown performance back to back is a very bad test procedure to use.
All that can be determined is the degree of mismatch at the unbalanced port and the insertion loss of the balun. This test procedure is incapable of revealing values for the mode conversion parameters which means that the CMRR cannot be calculated, and even worse, provides no conclusive evidence that the balun actually functions as a balun at all!
A procedure to test a balun using a conventional 2-port VNA which determines the CMMR but does not measure the insertion loss or the port reflection coefficients is detailed in [113]. This test procedure requires three precision resistors and the accuracy of the measurement is dependent upon the accuracy of these resistors.”

With ref 113 being “O. M. Woodward, “Balance Quality Measurements on Baluns,” IEEE Transactions on Microwave Theoiy and Techniques, vol. 31, no. 10, pp. 821-824, Oct. 1983.” I have not located this, so no further comment on the technique at present.

This to me raises questions concerning the validity of using baluns in the measuring chain; what exactly is being measured and is making back-back compensation measurements valid, especially if one is using home made baluns. The same might well apply to commercial ones.

I did a little research in to commercial baluns, “mini-Circuits” produce a very wide range of rf transformers (500+), there may be something suitable there, I have yet to explore possibilities


Summarising so far on the way to measure a cmc depends rather on the objective, is it to find parameters for a model or to evaluate performance, different approaches are required. There is no universally applicable model for cmc’s it depends if low frequency or rf application. Your own experiments and studies support this when you say “The 'equivalent' circuit maps the best my remeasurements is the model of Guanella (to ideal transformers; a transmission line to represent the DM and a reactance+resistance to represent the CM)”.


Kind regards

Ed, G8FAX

My quick notes about used foumulas in NanoVNA

Yes side-by-side as you put it. The NanoVNA is calculating all the parameters (SWR,
Return Loss (logmag format) and impedance (R, X) from the same scanned measurements.

Hello

I saw and verified that we can recalculate all the parameters from S11. Can you explain to me :
- What is the native measurement performed at the bridge level
- What is the first parameter produced by the nanoVNA from this native measurement
--
Fran?ois

-----Message d'origine-----

De la part de Roger Need via

Envoyé : dimanche 17 juillet 2022 22:33

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Very unlikely.? ? If you mate and remove a UFL about a dozen times, it no longer makes a good repeatable connection.? ?Really a connector designed to be used once during the assembly of a product.? Kent WA5VJB

Hello. I bought NanoVNA V2 Plus 4 Pro from tindle webpage.
In the package, I got cables and SMA calibration kit (4pcs). But this calibration kit is for SMA cables;



I have this Nordic NRF52840 Bluetooth kit. The kit has SWF RF connector for direct RF measurements.
My plan was to connect the NanoVNA to the SWF connector.

For better results, are there UFL or SWF calibration kits?
I use Murata MXHS83QE3000 SWF probe, and I want to calibrate the NanoVNA when this SWF probe is on.
But I can't find SWF calibration kit. Where can I find a SWF calibration kit?

Thank you, Gracias. Josele

On Sun, Jul 17, 2022 at 06:42 AM, Observer wrote:

another silly mistake !
I didnt realise that the short circuit cap is actually screwed in on the Ch0
and CH1 !!!

You should also have a barrel connector (threaded on both ends) to connect the cables together for the calibration through test. As a new user you should read the Absolute Beginners Guide to the NanoVNA.


Roger

On Sun, Jul 17, 2022 at 01:17 PM, <cariboome@...> wrote:

My question is: for some tuning, I often show a very low SWR (<1:1.05) with a
logmag reading of -15 or thereabouts, and another tune showing about the same
SWR but a logmag of -40, -50 or even -90 dB. The logmag trace sometimes
appearing as a very steep and deep notch, often at or in the SWR trace and
other times just a shallow dip. The Smith typically shows a fairly consistent
50 ohms plus or minus 1 or 2 at tuned resonance. Is this a representation of
reflected loss and VSWR being shown real time side by side? Is it better to
have a logmag reading of -90 dB let's say, as well as a very low SWR -- vs
very low SWR and a "higher" logmag of -20dB for instance?

Yes side-by-side as you put it.. The NanoVNA is calculating all the parameters (SWR, Return Loss (logmag format) and impedance (R, X) from the same scanned measurements. If your return loss is 14 dB you have a VSWR of about 1.5 which is fine for most purposes. If your SWR is higher than this modern solid state transmitters tend to cut back on their power output. A VSWR of 1.1 is a RL of 26 dB and that is excellent. Here is a link to a table of VSWR vs Return Loss. It also shows the reflected and through power. You should also be aware that Return Loss is a positive number but many publications use a negative sign which is not correct but done anyway. Yes confusing but the way it is...



Roger

Good day. I'm fairly new to both amateur radio and this marvelous device, the NanoVNA H4 v4.3 sold by Seesii on Amazon.ca
I find tuning my many inverted V antennas using a manual tuner extremely effective using this Nanovna -- set to s11 on 3 parameters for logmag, Smith and SWR traces.

My question is: for some tuning, I often show a very low SWR (<1:1.05) with a logmag reading of -15 or thereabouts, and another tune showing about the same SWR but a logmag of -40, -50 or even -90 dB. The logmag trace sometimes appearing as a very steep and deep notch, often at or in the SWR trace and other times just a shallow dip. The Smith typically shows a fairly consistent 50 ohms plus or minus 1 or 2 at tuned resonance. Is this a representation of reflected loss and VSWR being shown real time side by side? Is it better to have a logmag reading of -90 dB let's say, as well as a very low SWR -- vs very low SWR and a "higher" logmag of -20dB for instance?

I sincerely hope I'm expressing myself sensibly...
--
- Dave
-VA7WNW-

On 7/17/22 6:17 AM, Larry Martin wrote:

I work with RFID/NFC at 13.56 MHz, and have been using my NanoVNA with a nonresonant loop to check the resonant frequency of HF tags. I'm wondering if the radio experts here can tell me if other measurements are reasonable. Here is the setup (172KB jpeg):

The top picture shows the loop with nothing on it, a near perfect short with a little inductance. The bottom view shows the loop with a typical NFC inlay on top. Resonant frequency is a little high. That's the only objective measure I can really define with this setup.
I would love to be able to point to the depth of the LOGMAG traces as some kind of inlay strength indicator. Informally, I like to compare incoming tags with the one in the link to see if it has as-good LOGMAG deflection (this tag type is the best so far), but I can't convince anyone else of anything based on that observation. I'm wondering if someone with more radio knowledge can think of a way to make a sensitivity measurement out of that, so I could tell my customers whether they are getting good tags from their vendors.

What you're sort of measuring here is a combination of the coupling to the tag, and the mismatch of the load on the tag. Think of the equivalent circuit as being a transformer (your loop and the loop on the tag) coupled to some load. So the "mismatch" you see in the S11 is a combination of the coupling ratio and the actual load.

The actual load may or may not be 50 ohms in the design circuit. Since the receiver and transmitter are typically connected right to the tag's antenna, traditional "matched transmission line" might not be relevant.

You might be able to set up a test rig to do incoming inspection on theoretically identical tags (same make and model) - whatever the mismatch and frequency is, it should be the same.

But it's not necessarily a good way to compare different kinds of tags. Maybe one mfr designs for 150 ohms and another designs for 50 ohms and yet another designs for 10 ohms.

Couple notes:
* this works with _some_ EMI field probes.
* this also works at UHF (902-928 MHz), with _a few_ field probes.
* I know there is test equipment for this, $25k and up.

Try placing the antenna in a different location.... far away from anything metal/magnetic... - such items could be detuning the antenna... also, try using a longer test cable, so as to keep the VNA away from the antenna...say 5 feet or so, being sure to re-calibrate with the longer test cable...

Brian - KI8KY

another silly mistake !
I didnt realise that the short circuit cap is actually screwed in on the Ch0 and CH1 !!!

I work with RFID/NFC at 13.56 MHz, and have been using my NanoVNA with a nonresonant loop to check the resonant frequency of HF tags. I'm wondering if the radio experts here can tell me if other measurements are reasonable. Here is the setup (172KB jpeg):


The top picture shows the loop with nothing on it, a near perfect short with a little inductance. The bottom view shows the loop with a typical NFC inlay on top. Resonant frequency is a little high. That's the only objective measure I can really define with this setup.

I would love to be able to point to the depth of the LOGMAG traces as some kind of inlay strength indicator. Informally, I like to compare incoming tags with the one in the link to see if it has as-good LOGMAG deflection (this tag type is the best so far), but I can't convince anyone else of anything based on that observation. I'm wondering if someone with more radio knowledge can think of a way to make a sensitivity measurement out of that, so I could tell my customers whether they are getting good tags from their vendors.

Couple notes:
* this works with _some_ EMI field probes.
* this also works at UHF (902-928 MHz), with _a few_ field probes.
* I know there is test equipment for this, $25k and up.

Hi,

Check what you ordered, what should have been included, parts might be missing.

Typically, 4 calibration components supplied with the nanoVNA.

If this is not a supply problem, calibration kits are available, for example

Kind regards

Ed

You may decide that for yourself.

Anything goes. :-)


Op 17-7-2022 om 09:38 schreef Observer:

My newly received nanovna, has only two test connectors, plus two leads and the pen.
Do they expect me to make the missing short circuit connector, myself ?
It may seem a silly question, but, I am a totally newbie , nerd .

Think "terminal velocity" . . .

--
Sent from my Android device with K-9 Mail. Please excuse my brevity.