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Antenna experimenting has caused me to wish for another feature addition to the NanoVNA firmware library.
The new "resonance" search is very handy.
Now I'd like to see a more complicated-to-design feature that would analyze, characterize and hopefully identify toroid cores.
I'm interested in their use as transformers and as chokes. I like to work with loops, which need a choke balun, and with random wire antennas, with a need for a good transformer. (The random wire antenna is where the new resonance search feature comes in handy - avoiding any resonance in a ham band).
--
Doug, K8RFT

On 11/8/22 3:49 PM, DougVL wrote:

Antenna experimenting has caused me to wish for another feature addition to the NanoVNA firmware library.
The new "resonance" search is very handy.
Now I'd like to see a more complicated-to-design feature that would analyze, characterize and hopefully identify toroid cores.
I'm interested in their use as transformers and as chokes. I like to work with loops, which need a choke balun, and with random wire antennas, with a need for a good transformer. (The random wire antenna is where the new resonance search feature comes in handy - avoiding any resonance in a ham band).

I'd suggest that as a start, this be a feature to one of the PC applications that controls a NanoVNA. Or a standalone application.

It's hard to fit things into the firmware, and at some point there needs to a triage. The other thing is that one wants to have firmware that is fairly "model indpendent" so you don't wind up in a situation where some of your NanoVNAs run different versions than others.

Actually, a *very* cool thing would be if someone could start writing Apps that use Bluetooth to talk to the VNA. I know some folks have put a BT module on the serial port. Then you can develop all manner of specialized applications that would work on a tablet or phablet or phone (phone would be nice when up on a ladder, roof, or tower)

I'm not sure if a Android phone can be a USB master - it probably can. But iPhones are a bit more locked down, and don't have a USB port on them anyway.

BT serial port also won't raise issues with the "sandbox" provided by the phone mfrs - it's hard to "do bad things" with a serial port.

On Tue, Nov 8, 2022 at 03:49 PM, DougVL wrote:

Now I'd like to see a more complicated-to-design feature that would analyze,
characterize and hopefully identify toroid cores.
I'm interested in their use as transformers and as chokes.

This feature is already in NanoVNA Saver. Wind a few turns on the ferrite. Select the graph shown below and look for the "crossover" frequency. Then compare that with manufacturer specs for complex permeability "crossover" frequency (each mix is different).

Roger

On Tue, Nov 8, 2022 at 08:55 PM, Roger Need wrote:

This feature is already in NanoVNA Saver.

Thanks!!
That should be very helpful. I will try it out very soon - several unknown cores to investigate.
--
Doug, K8RFT

I come back to de Graph S11 R/ω & X/ω (?Ω/Hz)
Already, numerically, it's not /ω but /F (frequency). Do not forget to reset the graph
I still haven't understood what it can be for torus. How can we interpret this graph for an unknown toroid

Example (PJ) my toroid in testing (7 turns) made at the BF bridge 16 ?H between 1 kHz and 100 kHz. On Nanaovana-Saver in the Graph S11 Serial L (H) I see around 2 MHz 15.8 ?h. The value increases with the frequency, goes through a maximum 18 ?H to 5.7 MHz then descend to do 11 ?H to 16 MHz

On the graph S11 R/ω & X/ω (?Ω/Hz) the crossing of the curves is 13 MHz
How to interpret

73
--
F1AMM (Fran?ois)

The subject of measuring toroid characteristics (ferrite and powdered iron) has been discussed in this group before. When Rune added the graphing capability of S11 R/ω & X/ω to NanoVNA Saver there was a post on this subject. The post is 68 comments long and only a few pertain to this topic. The need for a decent test fixture and how to interpret the results is covered. Links to reference papers on the subject are provided.

/g/nanovna-users/message/6896

There was also a suggestion to add calculation of the complex permeability parameters ?' and ?'' to NanoVNA Saver on github. A lengthy discussion with spreadsheet calculations, test jig photos and documents on the subject were posted. Very interesting reading but it was never implemented in Saver.



The bottom line of all this discussion above is that it takes some effort to get accurate measurement results and it will be difficult to determine the manufacturer and mix type of an unknown toroid. If one knows the manufacturer (i.e. Fair-Rite) then determining the initial permeability and crossover frequency and comparing to data sheets will determine the mix type.

Roger

Again, Fair-Rite has a wonderful YouTube presentation that outlines how to
determine the mix of a ferrite. There's also a lot of additional
information which may be quite useful. Visit the Fair-Rite site and
explore their presentations.

Dave - W?LEV

On Wed, Nov 9, 2022 at 7:35 PM Roger Need via groups.io <sailtamarack=
[email protected]> wrote:

The subject of measuring toroid characteristics (ferrite and powdered
iron) has been discussed in this group before. When Rune added the
graphing capability of S11 R/ω & X/ω to NanoVNA Saver there was a post on
this subject. The post is 68 comments long and only a few pertain to this
topic. The need for a decent test fixture and how to interpret the results
is covered. Links to reference papers on the subject are provided.

/g/nanovna-users/message/6896

There was also a suggestion to add calculation of the complex permeability
parameters ?' and ?'' to NanoVNA Saver on github. A lengthy discussion
with spreadsheet calculations, test jig photos and documents on the subject
were posted. Very interesting reading but it was never implemented in
Saver.



The bottom line of all this discussion above is that it takes some effort
to get accurate measurement results and it will be difficult to determine
the manufacturer and mix type of an unknown toroid. If one knows the
manufacturer (i.e. Fair-Rite) then determining the initial permeability and
crossover frequency and comparing to data sheets will determine the mix
type.

Roger

--
*Dave - W?LEV*
*Just Let Darwin Work*


--
Dave - W?LEV

On Wed, Nov 9, 2022 at 07:52 AM, DougVL wrote:

several unknown cores to investigate.

Try it with some known cores first.
--
John AE5X

I found this data a year ago -

"The easiest way to identify most ferrite materials is to wind about four turns of wire through the core and then measure the lowest frequency at which the value of reactive impedance equal resistive impedance i.e. X=R. There will be some variation between different batches and sizes of materials. But if you can plot the results graphically you can easily identify the 'signature' of each material.

Here are my references for some common ferrite materials

FT240-77 0.74MHz
FT240-31 3.5MHz
FT100-33 7MHz
FT240-43 17MHz
FT240-K 22MHz
FT240-52 31MHz
FT240-61 58MHz

Iron powder has a slightly different 'signature' it usually has a very low resistive component, which peaks to a higher value near self resonance. The more lossy the material the broader and lower value of resistive peak is apparent.

T200-52 40MHz Lime Green (& Blue or Red) colour common in PC switch mode power supplies - moderate loss
T200-26 60MHz Yellow & White colour common in PC switch mode power supplies - high loss
T200-2 60MHz Dark Red colour used for HF tuned circuits (& Ruthoff Ununs) - high Q low loss
T200-1 70MHz Blue colour not common - moderate loss
T200-6 100MHz Yellow colour used for VHF tuned circuits - high Q low loss

To illustrate this point here are some loss measurements made on ring cores recovered from switched mode power supplies.

In each case the windings were 5 turns of 1mm wire bifilar wound as a 1:1 transformer. As you can see there is great deal of variation between the results depending upon the type of core material.

Powdered iron cores are popular for high power baluns, but they don’t offer much inductance per turn of wire, so their effectiveness when used as baluns can be limited. Ferrite materials provide a much higher impedance value per turn of wire and are much more effective over a wider frequency range, but they can be very lossy when connected to a mismatched load, and heat up to a point where irreversible damage occurs."
----------------
At this web address:


Using G8JNJ's data for matching the crossover frequency where X=R for the toroid being tested, I believe I've determined the mix type for a few unknown cores. The two I was most interested in were both roughly 2 inches diameter, but one was thick, heavy and all black and the other is painted gray with yellow around one edge. The X=R points were very close to the same value for each of those two cores, and were the same as Mix 77.

G8NJNJ's page was the only place that I found the crossover X=R frequencies data listed. I feel very grateful to him for publishing the data.

--
Doug, K8RFT

What is needed is some kind of NTE/ECG/SK catalog for most of the makers/seller of core material. Found this a long time ago and not sure if this will be useful to anybody. See attached.

Also, is there an SDK-ish docs on interfacing with the Nano? I was a fair programmer and I am learning to use my Nano better or at least trying to.

Michael

On Thu, Nov 10, 2022 at 11:36 PM, Michael wrote:
Michael -

Found this a long time ago and not sure if this will be useful to anybody. See
attached.

Your "cross_ref_list.pdf" sort of opens - appears blank and closes immediately.
--
Doug, K8RFT

It opens fine for me.
Max

For me too
Opens fine
Dg9bfc sigi

Am 11.11.2022 12:57 schrieb "Max via groups.io" <kg4pid@...>:

Hello,
The PDF file works fine for me also.
Maybe you need to download it again?
Clyde KC7BJE