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To start Ebay has plenty, look for mak1939. He also carries the R40C1 toroids and rods. You can easily get Qs over 1000 with his toroid and litz.

Here is mak's Ebay site,

The second thing to try is spacing your wire one wire width apart, that will increase your Q. I have 4 inch diameter coil 4-7/8 inch long using # 18 wire

and spaced one wire width apart that has a Q of 410 at 1Mhz. I also have a coil on a 6" styrene pipe coupler using 660/46 litz wire at 10 turns per inch.

It has a peak Q of 1450 at 800kHz and 1400 at 1Mhz. This was measured with a Boonton 260 Q meter with an external meter and using the 3 db method.

But, admittedly high Q measurements are finicky, changing orientation affects Q and an am radio signal near your test frequency will affect it and getting within 2 ft will lower Q.

You might like this where I tested multiple 6" styrene core coils with wire spaced between 7TPI and 12TPI to see where the highest Q was.

?????????????????????? Mikek



On 10/20/2021 10:17 AM, Andrew Kurtz via groups.io wrote:

Thanks, Manfred, this is incredibly helpful to a totally novice crystal radio builder! I see that low permeability is best for my application, which greatly reduces the “advantage” of needing very few turns compared to an air core. As a hobbyist, none of the factors important to a design engineer matter to me except my single goal: get the highest Q possible in my AM tuning circuit so I can get selectivity and separate the various stations that overlap. My current best is 41 turns on a Clorox bottle with Q = 130 or so. I believe the only way to improve this would probably (?) not involve an iron or ferrite core, but would use litz wire. Litz wire seems absolutely unavailable! Anyone know where to find some?

Andy

On Oct 20, 2021, at 11:03 AM, Manfred Mornhinweg <manfred@...> wrote:

Engineering is the art of finding workable compromises. Let's leave perfection to the philosophers.

When a electronic engineer needs an inductor in a circuit, it would be really rare that the requirements are: "Absolutely possible highest Q, and all other factors are irrelevant". Usually the situation is much harder: The name of the game is finding the most convenient way to implement that inductor, balancing all the many requirements: Inductance, Q (or loss factor, more commonly used by engineers), AC current handling, DC current handling, size, shape, weight, cost, ease of manufacturing, availability, accuracy, stability (relative to temperature, aging, etc), stray fields (self-shielding), and several more. The Q very often doesn't need to be as high as possible. It just needs to be high enough! For example, if one makes a lowpass filter for a low-power application, that works at a loaded Q of unity, the difference in performance between using very poor coils having a Q of 30, or very good ones having a Q of 300, is completely irrelevant! Current handling also doesn't need to be high, stability might not need to be great, and so on. So there is a lot of room to optimize those coils for size and cost, rather than for Q. Instead when building a lowpass filter for a high power transmitter, Q becomes important simply because it will define how much power the coil will have to dissipate as heat. Also AC current handling will need to be high. Stability and accuracy still don't need to be brilliant. So the engineer will choose very different coils here, large enough and and with high enough Q, that they won't overheat and won't run into nonlinearity problems. They will be much larger and much more expensive.

But in either case, a coil wound on a magnetic core will very often be a better choice than one having an air coil. The engineer has the freedom to choose the best option.

Why a coil on a core is often better: It tends to be much smaller. Often it's lighter too. The Q in some cases might actually be better than for an air core coil. This happens when the savings in copper loss, gained by shrinking the coil, are greater than the core losses introduced.

Of course there are cases where cores are a bad idea. For example, when someone is building a VFO. An extremely important requirement here is stability, and most core materials result in poorer stability than air-cored coils. Q is also important, because it has a large effect on the phase noise produced by the VFO. So one would typically choose an air cored coil, and make it pretty large, and wind it on the most stable former one can find. But if space is restricted, a coil wound on one of the more stable powdered iron material toroids might work better than a miniaturized air coil.

Using a mystery toroid and measuring very poor performance at a given frequency, is no reason to declare that all toroidal cores are bad, and that air-core coils are generally and always better! There are hundreds, if not thousands of different core materials available. Each of those has its own characteristics, and they include a two-dimensional permeability versus frequency curve, which tells the frequency range in which that material provides high Q, among other things.

In the example given many posts ago, my calculations end up with that mystery toroid having a permeability of roughly 6000. So it must be one of those extra high permeability ferrites, used mainly for noise suppression in EMI filtering chokes. This material can give good Q only on low frequencies, in the audio range. In fact, only in the lower audio range!

If anyone wants to try building ferrite-cored coils that beat air core coils in Q, in the megahertz range, I suggest trying toroids made from the lowest permeability grades of ferrite available. They commonly have either a permability of either 20 or 40. A fair comparison might be to take such a toroid, wind 15 turns of very thick wire on it, measure what inductance it gives, then wind an air coil of about the same size, designed to have the same inductance (many more turns, necessarily much thinner wire). Then compare the Q curves over frequency for both coils, and see which wins in which frequency range. I would not be surprised if there is a wide range in which the ferrite-cored coil is better.

Other fair comparisons could be between such a ferrite coil, and an air coil weighing the same, even if it's larger, or costing the same. In those cases air coils might end up better positioned. And for homebrewers, a very important point influencing decisions is that ferrite cores of specific materials need to be bought, usually online, with a waiting time. It's often far more attractive to wind an air coil, and be done with it! And cheaper too.

But measuring a ferrite outside its intended operation frequency range is unfair! The trade union of ferrite cores will bitterly complain, and mount a riot! :-)

--
This email has been checked for viruses by Avast antivirus software.

On Wed, Oct 20, 2021 at 09:05 AM, Jim Lux wrote:

It occurs to me that one could write a software application, either on a host
computer, or as alternate firmware for the NanoVNA that would work as a
"identify the mystery toroid".

Run a couple turns through the core, measure the S11 over a broad frequency
range to get a rough idea, then run a narrower span, and you should be able to
automatically compare to a collection of published materials and core
dimensions. (FairRite, for example, publishes .xls files for all their
materials)

One method is to find the frequency where R and X cross. That corresponds to where the complex permeability values μ′ and μ″ cross and is unique to each ferrite Mix.

Roger

Roger

It occurs to me that one could write a software application, either on a host computer, or as alternate firmware for the NanoVNA that would work as a "identify the mystery toroid".


Run a couple turns through the core, measure the S11 over a broad frequency range to get a rough idea, then run a narrower span, and you should be able to automatically compare to a collection of published materials and core dimensions. (FairRite, for example, publishes .xls files for all their materials)

On 10/20/21 8:17 AM, Andrew Kurtz via groups.io wrote:

Thanks, Manfred, this is incredibly helpful to a totally novice crystal radio builder! I see that low permeability is best for my application, which greatly reduces the “advantage” of needing very few turns compared to an air core. As a hobbyist, none of the factors important to a design engineer matter to me except my single goal: get the highest Q possible in my AM tuning circuit so I can get selectivity and separate the various stations that overlap. My current best is 41 turns on a Clorox bottle with Q = 130 or so. I believe the only way to improve this would probably (?) not involve an iron or ferrite core, but would use litz wire. Litz wire seems absolutely unavailable! Anyone know where to find some?

Andy

In AM BCB applications, a bar core with a lot of turns is often used to be more compact. Hard to fit that clorox bottle in your pocket, after all.? Since the signals are strong, background noise is high, and gain is cheap (today) then the loopstick is a decent choice.


In the "crystal radio" scenario (no gain, just a detector, driving high Z headphones), the air core might give better overall performance, if only because of higher "efficiency" in terms of the antenna impedance and detector characteristics.

Thanks, Manfred, this is incredibly helpful to a totally novice crystal radio builder! I see that low permeability is best for my application, which greatly reduces the “advantage” of needing very few turns compared to an air core. As a hobbyist, none of the factors important to a design engineer matter to me except my single goal: get the highest Q possible in my AM tuning circuit so I can get selectivity and separate the various stations that overlap. My current best is 41 turns on a Clorox bottle with Q = 130 or so. I believe the only way to improve this would probably (?) not involve an iron or ferrite core, but would use litz wire. Litz wire seems absolutely unavailable! Anyone know where to find some?

Andy

Engineering is the art of finding workable compromises. Let's leave perfection to the philosophers.

When a electronic engineer needs an inductor in a circuit, it would be really rare that the requirements are: "Absolutely possible highest Q, and all other factors are irrelevant". Usually the situation is much harder: The name of the game is finding the most convenient way to implement that inductor, balancing all the many requirements: Inductance, Q (or loss factor, more commonly used by engineers), AC current handling, DC current handling, size, shape, weight, cost, ease of manufacturing, availability, accuracy, stability (relative to temperature, aging, etc), stray fields (self-shielding), and several more. The Q very often doesn't need to be as high as possible. It just needs to be high enough! For example, if one makes a lowpass filter for a low-power application, that works at a loaded Q of unity, the difference in performance between using very poor coils having a Q of 30, or very good ones having a Q of 300, is completely irrelevant! Current handling also doesn't need to be high, stability might not need to be great, and so on. So there is a lot of room to optimize those coils for size and cost, rather than for Q. Instead when building a lowpass filter for a high power transmitter, Q becomes important simply because it will define how much power the coil will have to dissipate as heat. Also AC current handling will need to be high. Stability and accuracy still don't need to be brilliant. So the engineer will choose very different coils here, large enough and and with high enough Q, that they won't overheat and won't run into nonlinearity problems. They will be much larger and much more expensive.

But in either case, a coil wound on a magnetic core will very often be a better choice than one having an air coil. The engineer has the freedom to choose the best option.

Why a coil on a core is often better: It tends to be much smaller. Often it's lighter too. The Q in some cases might actually be better than for an air core coil. This happens when the savings in copper loss, gained by shrinking the coil, are greater than the core losses introduced.

Of course there are cases where cores are a bad idea. For example, when someone is building a VFO. An extremely important requirement here is stability, and most core materials result in poorer stability than air-cored coils. Q is also important, because it has a large effect on the phase noise produced by the VFO. So one would typically choose an air cored coil, and make it pretty large, and wind it on the most stable former one can find. But if space is restricted, a coil wound on one of the more stable powdered iron material toroids might work better than a miniaturized air coil.

Using a mystery toroid and measuring very poor performance at a given frequency, is no reason to declare that all toroidal cores are bad, and that air-core coils are generally and always better! There are hundreds, if not thousands of different core materials available. Each of those has its own characteristics, and they include a two-dimensional permeability versus frequency curve, which tells the frequency range in which that material provides high Q, among other things.

In the example given many posts ago, my calculations end up with that mystery toroid having a permeability of roughly 6000. So it must be one of those extra high permeability ferrites, used mainly for noise suppression in EMI filtering chokes. This material can give good Q only on low frequencies, in the audio range. In fact, only in the lower audio range!

If anyone wants to try building ferrite-cored coils that beat air core coils in Q, in the megahertz range, I suggest trying toroids made from the lowest permeability grades of ferrite available. They commonly have either a permability of either 20 or 40. A fair comparison might be to take such a toroid, wind 15 turns of very thick wire on it, measure what inductance it gives, then wind an air coil of about the same size, designed to have the same inductance (many more turns, necessarily much thinner wire). Then compare the Q curves over frequency for both coils, and see which wins in which frequency range. I would not be surprised if there is a wide range in which the ferrite-cored coil is better.

Other fair comparisons could be between such a ferrite coil, and an air coil weighing the same, even if it's larger, or costing the same. In those cases air coils might end up better positioned. And for homebrewers, a very important point influencing decisions is that ferrite cores of specific materials need to be bought, usually online, with a waiting time. It's often far more attractive to wind an air coil, and be done with it! And cheaper too.

But measuring a ferrite outside its intended operation frequency range is unfair! The trade union of ferrite cores will bitterly complain, and mount a riot! :-)

I have also used them as inter-stage transformers. They make great
broadband transformers between stages or devices.

73, Zack W9SZ

Why does anyone use a ferrite toroid for anything??

Ferrite cores are used for RFI suppression chokes, where we *want* losses.

73, John W1JA

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Andrew Kurtz via groups.io
Sent: Tuesday, October 19, 2021 9:36 PM
To: [email protected]
Subject: Re: [nanovna-users] "Q", Coils, toroids, and guesswork?

I am really getting a lesson here! I have a homemade coil of 40 turns on a Clorox bottle, so length about equals diameter, intended to be best Q possible. Q is 130 based on X and R reported by nanoVNA at 1 MHz, where I use this coil. Note that this coil has 60 FEET of wire, and skin effect (I assume) makes R = 11 ohms or about 100 times DC resistance.

Then I wind 6 turns on my mystery ferrite toroid, using 10 INCHES of wire, and I get about the same inductance (180 uH versus 200 for the large air-core coil). And of course I get about the same reactance at the same frequency…… but R rises to 200 ohms at 600 kHz and over 1000 ohms at 1 MHz!! I guess there is hysteresis, eddy currents, etc., but I expected that this much smaller coil with much less wire would be the best Q possible short of having litz wire… but the Q of the toroid is around 1. Why does anyone use a ferrite toroid for anything??

Anyone know where I can acquire some litz wire?

Andy

On Oct 19, 2021, at 7:23 PM, Jim Lux <jim@...> wrote:

On 10/19/21 3:48 PM, W0LEV wrote:

What could be higher Q (lowest possible losses) than air or vacuum?
Ferrite and powdered iron toroidal cores have a higher ?r which
yields higher inductance per turn than free space, but there are
associated losses. Air core inductors are the highest Q attainable,
all other variables being equal. Anything wound on ferrite or
powdered iron cores will exhibit lower Q than wound in free space.

Dave - W?LEV

Oddly, not necessarily. Yes, the same windings, with a core, will have higher L and lower Q, because of core losses. However, if you compare equal inductance and current handling ability, you might wind up with a LOT of turns (and a very long wire) so the wire losses are higher than the core losses on a inductor on a core.

Go to the Micrometals web site. Take a look at their various mix of iron powder cores. You can mix and match size, L and perm
values to see what Q is achieved. Unloaded Q value excess of 400 is quite straight forward. They may still provide their Q curves text. Nice reference.

Use a different core, litz wire is useful up to about 3MHz, higher than that
it provides no benefits.

On Wed, 20 Oct 2021 at 03:36, Andrew Kurtz via groups.io <adkurtz=
[email protected]> wrote:

I am really getting a lesson here! I have a homemade coil of 40 turns on
a Clorox bottle, so length about equals diameter, intended to be best Q
possible. Q is 130 based on X and R reported by nanoVNA at 1 MHz, where I
use this coil. Note that this coil has 60 FEET of wire, and skin effect (I
assume) makes R = 11 ohms or about 100 times DC resistance.

Then I wind 6 turns on my mystery ferrite toroid, using 10 INCHES of wire,
and I get about the same inductance (180 uH versus 200 for the large
air-core coil). And of course I get about the same reactance at the same
frequency…… but R rises to 200 ohms at 600 kHz and over 1000 ohms at 1
MHz!! I guess there is hysteresis, eddy currents, etc., but I expected
that this much smaller coil with much less wire would be the best Q
possible short of having litz wire… but the Q of the toroid is around 1.
Why does anyone use a ferrite toroid for anything??

Anyone know where I can acquire some litz wire?

Andy

On Oct 19, 2021, at 7:23 PM, Jim Lux <jim@...> wrote:

On 10/19/21 3:48 PM, W0LEV wrote:

What could be higher Q (lowest possible losses) than air or vacuum?
Ferrite and powdered iron toroidal cores have a higher ?r which yields
higher inductance per turn than free space, but there are associated
losses. Air core inductors are the highest Q attainable, all other
variables being equal. Anything wound on ferrite or powdered iron cores
will exhibit lower Q than wound in free space.

Dave - W?LEV

Oddly, not necessarily. Yes, the same windings, with a core, will have

higher L and lower Q, because of core losses. However, if you compare equal
inductance and current handling ability, you might wind up with a LOT of
turns (and a very long wire) so the wire losses are higher than the core
losses on a inductor on a core.

It is as simple as the ferrite material you have is very lossy. There
are much better ferrite materials to use at 1Mhz.

With a proper core and litz wire, you can get the R under 1 ohm.

???????????????????????????????????????????????????? Mikek

On 10/19/2021 8:36 PM, Andrew Kurtz via groups.io wrote:

I am really getting a lesson here! I have a homemade coil of 40 turns on a Clorox bottle, so length about equals diameter, intended to be best Q possible. Q is 130 based on X and R reported by nanoVNA at 1 MHz, where I use this coil. Note that this coil has 60 FEET of wire, and skin effect (I assume) makes R = 11 ohms or about 100 times DC resistance.

Then I wind 6 turns on my mystery ferrite toroid, using 10 INCHES of wire, and I get about the same inductance (180 uH versus 200 for the large air-core coil). And of course I get about the same reactance at the same frequency…… but R rises to 200 ohms at 600 kHz and over 1000 ohms at 1 MHz!! I guess there is hysteresis, eddy currents, etc., but I expected that this much smaller coil with much less wire would be the best Q possible short of having litz wire… but the Q of the toroid is around 1. Why does anyone use a ferrite toroid for anything??

Anyone know where I can acquire some litz wire?

Andy

On Oct 19, 2021, at 7:23 PM, Jim Lux <jim@...> wrote:

On 10/19/21 3:48 PM, W0LEV wrote:

What could be higher Q (lowest possible losses) than air or vacuum?
Ferrite and powdered iron toroidal cores have a higher ?r which yields
higher inductance per turn than free space, but there are associated
losses. Air core inductors are the highest Q attainable, all other
variables being equal. Anything wound on ferrite or powdered iron cores
will exhibit lower Q than wound in free space.

Dave - W?LEV

Oddly, not necessarily. Yes, the same windings, with a core, will have higher L and lower Q, because of core losses. However, if you compare equal inductance and current handling ability, you might wind up with a LOT of turns (and a very long wire) so the wire losses are higher than the core losses on a inductor on a core.

--
This email has been checked for viruses by Avast antivirus software.

I am really getting a lesson here! I have a homemade coil of 40 turns on a Clorox bottle, so length about equals diameter, intended to be best Q possible. Q is 130 based on X and R reported by nanoVNA at 1 MHz, where I use this coil. Note that this coil has 60 FEET of wire, and skin effect (I assume) makes R = 11 ohms or about 100 times DC resistance.

Then I wind 6 turns on my mystery ferrite toroid, using 10 INCHES of wire, and I get about the same inductance (180 uH versus 200 for the large air-core coil). And of course I get about the same reactance at the same frequency…… but R rises to 200 ohms at 600 kHz and over 1000 ohms at 1 MHz!! I guess there is hysteresis, eddy currents, etc., but I expected that this much smaller coil with much less wire would be the best Q possible short of having litz wire… but the Q of the toroid is around 1. Why does anyone use a ferrite toroid for anything??

Anyone know where I can acquire some litz wire?

Andy

My experience is in the AMBCB. Some have built air core coils with Qs
reaching 2000. This was with two pieces of 640/46 litz wire in parallel.

?The best toroid Q I have seen is around 1500. These were around 240uh,
the material was R40C1.

Might get better, but two litz wires in parallel won't fit on the toroid.

??????????????????????????????????????????????? Mikek

On 10/19/2021 6:23 PM, Jim Lux wrote:

On 10/19/21 3:48 PM, W0LEV wrote:

What could be higher Q (lowest possible losses) than air or vacuum?
Ferrite and powdered iron toroidal cores have a higher ?r which yields
higher inductance per turn than free space, but there are associated
losses.? Air core inductors are the highest Q attainable, all other
variables being equal.? Anything wound on ferrite or powdered iron cores
will exhibit lower Q than wound in free space.

Dave - W?LEV

Oddly, not necessarily.? Yes, the same windings, with a core, will
have higher L and lower Q, because of core losses. However, if you
compare equal inductance and current handling ability, you might wind
up with a LOT of turns (and a very long wire) so the wire losses are
higher than the core losses on a inductor on a core.

--
This email has been checked for viruses by Avast antivirus software.

You are correct, Jim, only for large inductances requiring lots of wire as
you stated. But for us "average" inductances, still the air core would
yield the highest Q.

Dave - W?LEV

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

On 10/19/21 3:48 PM, W0LEV wrote:

What could be higher Q (lowest possible losses) than air or vacuum?
Ferrite and powdered iron toroidal cores have a higher ?r which yields
higher inductance per turn than free space, but there are associated
losses. Air core inductors are the highest Q attainable, all other
variables being equal. Anything wound on ferrite or powdered iron cores
will exhibit lower Q than wound in free space.

Dave - W?LEV

Oddly, not necessarily.? Yes, the same windings, with a core, will have higher L and lower Q, because of core losses. However, if you compare equal inductance and current handling ability, you might wind up with a LOT of turns (and a very long wire) so the wire losses are higher than the core losses on a inductor on a core.

What could be higher Q (lowest possible losses) than air or vacuum?
Ferrite and powdered iron toroidal cores have a higher ?r which yields
higher inductance per turn than free space, but there are associated
losses. Air core inductors are the highest Q attainable, all other
variables being equal. Anything wound on ferrite or powdered iron cores
will exhibit lower Q than wound in free space.

Dave - W?LEV

On Mon, Oct 18, 2021 at 9:22 PM Andrew Kurtz via groups.io <adkurtz=
[email protected]> wrote:

Agreed, but isn’t that R, divided into X at 1 MHz, going to give me Q? It
will be terrible. I expected a toroid to offer higher Q than an air core…

On Oct 18, 2021, at 4:58 PM, KENT BRITAIN <WA5VJB@...> wrote:

? That 200 Ohms is not the same as a 200 Ohm resistor at any frequency

other that 1 MHz.

Again Impedance, not resistance. Kent
On Monday, October 18, 2021, 03:53:18 PM CDT, Andrew Kurtz via

groups.io <adkurtz@...> wrote:

Thanks, but I must disagree: the nanoVNA provides a resistance output

as well as a reactance, and that is what I was reading to be 200 ohms at 1
MHz...

On Oct 18, 2021, at 4:45 PM, KENT BRITAIN <WA5VJB@...> wrote:

Not really resistance, but impdeance.
Got a good old DC Volt Ohm Meter?
Try that, but you see only 1 or 2 Ohms.
Most of the Digital VOM;s are using pulses that are much like RF.So

they are reading as much AC impedance as DC resistance.

Kent
On Monday, October 18, 2021, 03:22:44 PM CDT, Andrew Kurtz via

groups.io <adkurtz@...> wrote:

This thread inspires me to ask a question that is not directly about my

nanoVNA: I have a toroid from a flea market that is blue, has OD = 0.875”,
ID = 0.51”, and length = 0.3125”. I wrapped 6 turns on it, and found (on
the VNA) that L is pretty stable around 180 uH. This indicates that Al
must be about 5000 mH/turns^2. ( I know NOTHING about toroids…) but some
reference has very few with Al in the range of thousands. Some of them
claim high Q, but the VNA indicates a (real) resistance of around 200 ohms
at 1 MHz!! This is insanely high; I have air-core inductors for the same
service with 60 FEET of wire showing R = 11 ohms at 1 MHz, and this
“high-Q” toroid, with 11 INCHES of wire, has R = 200 ohms!?! Am I
misunderstanding something? So:

- Is there a way to identify my toroid simply because of its size and

blue color?

- Is such a high Al, suggesting a very high initial permeability,

realistic?

- Why would adding a toroid to less than 1 foot of coil create 200

Ohms resistance?

Thanks!
Andy

On Oct 18, 2021, at 11:37 AM, Tom McKee K4ZAD <tom.m@...>

wrote:

On Sat, 16 Oct 2021 Cliff <mailto:kd4gt.tn@...?subject=Re:%20%22Q%22%2C%20Coils%2C%20toroids%2C%20and%20guesswork%3F>

wrote about an on line toroid calculator available at:

There is a similar Excel spreadsheet based calculator available for

download at:

This link is one of many in my collection of on-line coil calculators

available at:

<>

73,

Tom K4ZAD

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

On 10/18/21 6:04 PM, Roger Need via groups.io wrote:

On Mon, Oct 18, 2021 at 11:59 AM, Gary O'Neil wrote:

Some may find this does-it-all calculator useful also. It is my go to site for
all things toroid.
…. and even obvious and easy to remember and get to.

Just type the following in the address bar of your browser and hit enter.

Toroids.info

Gary,

There are several calculators online like the one at toroids.info that have a common error. They assume that the initial permeability is the same with frequency. This is not true with ferrite toroids. So if you wanted a ferrite toroid for operation at 3.6 MHz. and you calculated the number of turns required using this calculator you would find the inductance to be lower than expected at 3.6 MHz.

Here is an example. I wound a FT50-43 toroid with 4 turns of 28 AWG wire. Toroids.info gives and inductance of 7.04 uH (see attached graphic). Using a one port VNA (Rig Expert AA-55 Zoom) I measured 4 uh - a considerable difference. A better toroid calculator is needed.

Owen Duffy has covered ferrites extensively on his blog and publishes calculators which take "complex permeability" into account. Here is a link:


The first step using his calculators is to get the manufacturers data sheet and get Al and the initial permeability ?i for the toroid size and mix. For a FT50-43 it is 440 and 800 respectively. The next step is to calculate the complex permeability ?’ and ?” at the frequency of operation. Duffy provides a calculator to determine these values. At 3.6 Mhz. for Mix 43 we get ?’ = 470.2 and ?”. If we enter this into his inductance calculator we get 4.14 uH which is pretty close to the experimental results. Screenshots of the calculated inductance and measured data are attached.

That's the cool thing about Miguel Vaca's program - it takes the data from Fair-rite which gives mu' and mu'' vs frequency and does the calculations.

Those interested in the theory behind the Duffy Calculator should read this link:


Roger

On Mon, Oct 18, 2021 at 11:59 AM, Gary O'Neil wrote:

Some may find this does-it-all calculator useful also. It is my go to site for
all things toroid.
…. and even obvious and easy to remember and get to.

Just type the following in the address bar of your browser and hit enter.

Toroids.info

Gary,

There are several calculators online like the one at toroids.info that have a common error. They assume that the initial permeability is the same with frequency. This is not true with ferrite toroids. So if you wanted a ferrite toroid for operation at 3.6 MHz. and you calculated the number of turns required using this calculator you would find the inductance to be lower than expected at 3.6 MHz.

Here is an example. I wound a FT50-43 toroid with 4 turns of 28 AWG wire. Toroids.info gives and inductance of 7.04 uH (see attached graphic). Using a one port VNA (Rig Expert AA-55 Zoom) I measured 4 uh - a considerable difference. A better toroid calculator is needed.

Owen Duffy has covered ferrites extensively on his blog and publishes calculators which take "complex permeability" into account. Here is a link:


The first step using his calculators is to get the manufacturers data sheet and get Al and the initial permeability ?i for the toroid size and mix. For a FT50-43 it is 440 and 800 respectively. The next step is to calculate the complex permeability ?’ and ?” at the frequency of operation. Duffy provides a calculator to determine these values. At 3.6 Mhz. for Mix 43 we get ?’ = 470.2 and ?”. If we enter this into his inductance calculator we get 4.14 uH which is pretty close to the experimental results. Screenshots of the calculated inductance and measured data are attached.

I just tried to verify pulses on my Bryman BM235, I didn't find any
pulses, no matter what timebase I checked.

I put 610k across the meter with the scope. Just tested again without
the resistor, still no pulses.

??????????????????????????????????????????????? Mikek

On 10/18/2021 4:41 PM, KENT BRITAIN wrote:

Just may have to try that later.Ran into this issue when measuring windings on some transformers and getting impossibly high numbers.? ? Dug out the old Simpson, and saw about what I was expecting.? ? We both know that if you take a bit of wire that measures 1 Ohm, wrap it around a magnetic core, it will still read 1 Ohm.? At DC of course.? ? ?Otherwise you would never see all these switching power supplies.? Kent


On Monday, October 18, 2021, 04:33:56 PM CDT, Mikek <amdx@...> wrote:

That interesting! Maybe I'll be learning something here. What happens if
you measure a 100k resistor with 10uf capacitor across it?

On 10/18/2021 4:27 PM, KENT BRITAIN wrote:

? That's what I see when I hook up my Harbor Freight special to a Tek scope!
And on a Fluke meter as well.
Kent

? ? ? On Monday, October 18, 2021, 04:10:24 PM CDT, Mikek <amdx@...> wrote:

? Type J (75) was my first thought also, but his numbers, 1Mhz, 180uh and
200 ohms R, is a Q of 5 or 6 and I think that is much to low,

unless he used some high resistance wire.

To Kent, I have two disagreements, I don't think DVMs in the resistance
mode work the way you think they do.

And the idea that the OP has a coil that measures 180uh (1131Ω at 1Mhz)
can have 200 ohms of resistance is very possible.

I'm certain the OP know the difference between inductive reactance,
resistance and impedance.

Mikek

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