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Garry says:

“… Then attach your inductor. …”

The devil is in the details with such a simple-sounding statement. Attach it how? There are 2 ports on the NanoVNA, each with a center conductor and an outside conductor (called, shield, ground, body, etc.) The inductor (DUT) has a single conductor with 2 ends. So, exactly how do you connect those 2 ends to the NanoVNA ports? Considering there is also an option of leaving certain ports, wire ends, or conductors (center/shield) disconnected, there are more than 10 possible options.

Then, once some sort of connection is made between inductor and VNA, which measurement option (menu choice) do you select on the NanoVNA? S11, S21, shunt, thru, etc. This decision adds more complexity.

For those experienced/ trained in using VNA’s and deciding such things for multiple different types of DUT’s, these may be such basic questions as to be assumed inherently obvious. But they are not inherently obvious to the new VNA users attracted to forums such as these.

On 6/23/23 6:51 AM, Garry wrote:

The different measurement techniques usually arise due to the propagation of error. In the case of vna's the measurement methods relate to the impedance of the DUT. You will find a number of articles online describing how to mak accurate measurements. One such article is

Basically, a 1-port measurement works best around the 50 ohm port impedance, shunt-through works best for low impedance, and series-through works best for higher impedance.

I believe the original question was more about "how do I figure out which mix this unmarked toroid is" and for that, measurement accuracy may not be super important, especially if you have some known examples to compare to.

The nice thing about a VNA is you can easily sweep a wide frequency range, so you're looking for a "does my curve look more like curve A or curve B", rather than a single spot measurement at a single frequency and trying to figure out if your estimate of mu is correct.

The what do R and X look like vs frequency is a pretty good way to distinguish materials. And if there's a measurement error it might not perturb that much. What you're really looking for is "not lossy at frequency range X but lossy at frequency range Y"

The different measurement techniques usually arise due to the propagation of error. In the case of vna's the measurement methods relate to the impedance of the DUT. You will find a number of articles online describing how to mak accurate measurements. One such article is

Basically, a 1-port measurement works best around the 50 ohm port impedance, shunt-through works best for low impedance, and series-through works best for higher impedance.

I'm not sure that changing the measurement technique will help, unless you are experiencing significant errors. You might need to change your core size or even material to make inductors with less parallel capacitance and avoid self-resonance problems. I'm not an expert in filters, I have mostly built other people's designs and not a large number of them. But, it seems your problem may be the inductor construction.

Go to

then scroll WAY down to

"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"
-----------
and

--
and this page is long, but might also help ('way down the page)


------------------
And there's
"Name that Core" by Carl Luetzelschwab K9LA"
(a 2-page document for which I have no URL, just a printout of the text, with a graph and a chart.

OR this might work:
}
------------

You can also look back at this group's topic 72777666 for some more tips.
------------------------------------

Doug, K8RFT

FT240-43 Torroid, Can I use my NanoVNA to meassure my several torroids
to be sure that I have the correct ones for HF UNUN?
any info is welcome

Hello

Unun means nothing. You should know that the nature of the material of the torus is of great importance if you make a choke (self) with it. If you made a RUTHROFF transformer, it is much less important.

To test the torus, a self must be made. To measure the characteristics, enough turns are needed to cover the *entire* torus. My measurements were failing when I didn't do that. Count the number of coils carefully, you will need this number later. It is the number of wires visible inside the torus that counts; a wire that passes straight is counted as a turn.

You will thus be able to measure, with the NanoVNA, a self (?H) according to the frequency etc. You will be able to calculate the Al and you will be able to calculate the ?r which will allow you to check the nature of the material.

It is not at all an easy thing to do.

73
--
F1AMM
Fran?ois

De la part de Kurt Heernaert
Envoyé : mercredi 21 juin 2023 21:32

Hello

I was having an issue with RFI in my shack, I'm in an apartment and my MFJ loop is at the back of the office next to a window and my radio is an Icom IC-7300. I made a CM choke from a 240-31 ferrite toroid core and it solved the problem on 40 and 20 meters. I was still having problems on 17 and 15 meters so I got a 240-43 donut and made a CM choke and it pretty well cleared up my problems aside from a couple of problem areas which were solved by a few more 240-43 ferrite toriod cores. I made up a test jig for my NanoVNA from articles found on the net. I could post a picture if anyone in interested

Steve ve4fx

Garry,
my experiene: when trying the buid a bandpass filter (mesch coupled filter) with ELSIE I noticed that the series L?s are only dependant on the chosen bandwidth. In my case 17.5 uH was the series L. Winding this on a T37-2 toroid. gave full toroid (about 80 cm of wire).?The self resonance using my NANO VNA (channel 0, S11) showed about 12 MHz, Generating an S-parameter file and putting these results into RFSIM99 showed that I cannot use this filter even at 7 MHz!?
? Please explain? why? and wehn a two port measurement is more usefill!
Henning WeddigDK5LV? ??
Dipl. Ing. Henning Christof Weddig

Am Donnerstag, 22. Juni 2023 um 17:36:41 MESZ hat Garry <garry.heard@...> Folgendes geschrieben:

#### reply to Kurt's Toroid Measurement

It's quite easy to get a simple measurement on a toroid inductance and to see the inductor's behavior over a desired frequency band with a nanoVNA. So easy, I think it should be a matter of course for every build.

Getting the most accurate results requires using the proper set up for the expected impedance. Depending on the impedance, the measurement method will change. Using a simple one-port reflection measurement for impedances "somewhere" near 50 ohms is usually sufficient for a quick check. For higher and lower impedances, you'll have to change to a two-port series or shunt method.

To get a reasonable idea of the inductance and resistance of your toroid use a basic fixture and attach it to port 0. Set up the frequency start and stop values, switch to Smith Chart, and calibrate. Then attach your inductor. You will be able to see an estimate of the inductance at the desired frequency of operation. The inductor should create a trace in the upper half of the screen. The trace may be anything from a point to an arc along the entire outer edge of the display.

A good low-loss inductor should create a trace near the outside upper edge of the Smith Chart. If the trace moves inward from the edge, you have losses. If the trace crosses the horizontal axis, you have a self-resonance.

Don't be surprised if the readouts show unexpected results. The outcome really depends on where the toroid came from. Is it really the advertised material? Remember, that the A<SUB>L</SUB> values are usually for 10 kHz (the standard frequency) and your inductance might be quite a bit off what you expected if that is how you decided on the number of turns.

I like to check every component before I use it. I've been surprised by faulty parts. Often it's much harder to fix once you've assembled your circuit. A semiconductor tester, LCR meter, and nanoVNA generally get used on every part.

reply to Kurt's Toroid Measurement

It's quite easy to get a simple measurement on a toroid inductance and to see the inductor's behavior over a desired frequency band with a nanoVNA. So easy, I think it should be a matter of course for every build.

Getting the most accurate results requires using the proper set up for the expected impedance. Depending on the impedance, the measurement method will change. Using a simple one-port reflection measurement for impedances "somewhere" near 50 ohms is usually sufficient for a quick check. For higher and lower impedances, you'll have to change to a two-port series or shunt method.

To get a reasonable idea of the inductance and resistance of your toroid use a basic fixture and attach it to port 0. Set up the frequency start and stop values, switch to Smith Chart, and calibrate. Then attach your inductor. You will be able to see an estimate of the inductance at the desired frequency of operation. The inductor should create a trace in the upper half of the screen. The trace may be anything from a point to an arc along the entire outer edge of the display.

A good low-loss inductor should create a trace near the outside upper edge of the Smith Chart. If the trace moves inward from the edge, you have losses. If the trace crosses the horizontal axis, you have a self-resonance.

Don't be surprised if the readouts show unexpected results. The outcome really depends on where the toroid came from. Is it really the advertised material? Remember, that the A_L values are usually for 10 kHz (the standard frequency) and your inductance might be quite a bit off what you expected if that is how you decided on the number of turns.

I like to check every component before I use it. I've been surprised by faulty parts. Often it's much harder to fix once you've assembled your circuit. A semiconductor tester, LCR meter, and nanoVNA generally get used on every part.

Jim...All good points.

Yes, I have been thinking about a dedicated nanovna and fixture and the various options needed for different cable types. For the multi-channel snakes the VF is pretty similar as the construction and materials is similar. This would be the main use. And the stimulus scan frequencies will probably require changing as well.

I would like to make this as easy for individuals with varing technical experience. It might necessitate a PC connection but I have not researched that aspect...very new project.

Single mic cables can have a VF much lower, I've measured some less than 50%.

And yes the impedance is as you mention although manufacturers don't always specify except for AES/EBU whis in nominally 110 Ohms.

On 6/21/23 8:05 PM, Joe wrote:

I was just trying to point out that if you have a choice between using a short or open on any device, the short would minimize or eliminate interference that might enter the end of the cable.
Joe
On 6/21/2023 9:56 PM, Geoff Peters - AB6BT wrote:

Joe.. What I'm trying to do is locate a short or open in a multi-channel audio snake. I really can't afford the high priced spread...

You might make up some XLR cal loads - Open's easy. Short, and I'd go for a 100 or 120 ohm load, since it's probably shielded twisted pair.

But yeah, if you're looking for a fault somewhere in the middle, then shorting the far end minimizes hassles.

I assume you're not looking for a channel to channel short.

This is great non RF application for the NanoVNA.. you should write up how you did it and what you found out. WIth these sorts of things fixturing is what it's all about. If you've got a snake with XLR on both ends, then cobbling up some adapters is probably a good thing.

Propagation speed in a multichannel audio cable, whether shielded twisted pair or multiple coax is going to be something you'll have to figure out. But you know the physical length. FWIW, mic cables aren't 50 ohms, but you knew that.

On 6/21/23 6:56 PM, Geoff Peters - AB6BT wrote:

Joe.. What I'm trying to do is locate a short or open in a multi-channel audio snake. I really can't afford the high priced spread...

real mode will do you. I've used the NanoVNA on Cat 5 network cables. SMA to BNC: BNC to clipleads (EZ-Hook variety).

On 6/21/23 5:41 PM, Geoff Peters - AB6BT wrote:

Roger...I was in Logmag mode. I'll try Real tomorrow
Jim...In Logmag mode the short and open appear identical as far as I can tell

Log mag is *always positive* (it's absolute value)..
Yeah, you need to be in a linear signed mode

I was just trying to point out that if you have a choice between using a short or open on any device, the short would minimize or eliminate interference that might enter the end of the cable.

Joe

Joe.. What I'm trying to do is locate a short or open in a multi-channel audio snake. I really can't afford the high priced spread...

I do fault locating with the Anritsu SiteMaster and the CellMaster. I prefer to use a short when testing because it seals off the end of the cable and avoids/reduces interference. This can help when testing on a heavily RF populated site.

Joe

Roger...I was in Logmag mode. I'll try Real tomorrow

Jim...In Logmag mode the short and open appear identical as far as I can tell

On 6/21/23 2:22 PM, Geoff Peters - AB6BT wrote:

I realize this is similar to a recent topic but a bit different.
As the "TDR" function in the nanovan is not actually a time-domain process, is there a wat to differentiate between a short or open fault in a cable?
I have previously built a generator which can produce a very short pulse or a step with fast risetime. I have used it in conjunction with a scope as a TDR. It works reasonable well and you can clearly see an open or short in a cable.
Is there a way to replicate tis with a nanovna?

It should work identically - short and opens have 180 degree difference in the phase of the reflection, and that shows up in the synthetic TDR from the frequency sweep.

On Wed, Jun 21, 2023 at 02:45 PM, Robert Rose wrote:

This is a "where is Waldo" on the menu spider-web question. How do start a
rescan after I change parameters? Is there an FAQ that beginners should read?
A "NanoVNA for Dummies" book that you can recommend?

The Files section of this group contains an "Absolute Beginners Guide to the NanoVNA"

Roger

If you turn on Transform and select Low Pass Impulse you are in "TDR mode". You need to set trace to "Real" and then you will see the difference between a short and an open.

Roger

On Wed, Jun 21, 2023 at 02:52 PM, Robert Rose wrote:

On Tue, Jun 11, 2019 at 07:52 PM, Frank S wrote:

Is there a way to tell what rev the firmware is?

HOME MENU->CONFIG->VERSION

Why necropost? Lots of current discussions in this group.

Roger