Re: "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
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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.
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Re: "Q", Coils, toroids, and guesswork?
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.
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Re: "Q", Coils, toroids, and guesswork?
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
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On Tue, Oct 19, 2021 at 11:24 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.
-- *Dave - W?LEV* *Just Let Darwin Work*
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Re: "Q", Coils, toroids, and guesswork?
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.
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Re: "Q", Coils, toroids, and guesswork?
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*
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Re: "Q", Coils, toroids, and guesswork?
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.
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Re: "Q", Coils, toroids, and guesswork?
Those interested in the theory behind the Duffy Calculator should read this link:
Roger
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Re: "Q", Coils, toroids, and guesswork?
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.
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Re: "Q", Coils, toroids, and guesswork?
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 (1131¦¸ 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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Re: "Q", Coils, toroids, and guesswork?
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
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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 (1131¦¸ 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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Re: "Q", Coils, toroids, and guesswork?
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 (1131¦¸ 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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Re: "Q", Coils, toroids, and guesswork?
Andy,
The high loss R is, I believe, from the toroid ferrite material. This is why they are used for RF suppression, e.g. common mode choke baluns. K9YC has lots of material on this. See, e.g., , Chapter 2 has graphs showing R, L, X vs. frequency for different ferrite materials. For chokes you want a material that has high R (e.g. several 1000 Ohms) at the frequencies to be suppressed. For inductors you want to operate in a low R region.
73, Roger
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Re: "Q", Coils, toroids, and guesswork?
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
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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 (1131¦¸ 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 On 10/18/2021 4:00 PM, Zack Widup wrote: The closest thing I see to that is the Amidon type J ferrite toroids. Useful frequency range is 1 to 15 MHz for type J. They don't specify a size exactly the same, but the FT87-J is the closest they have.
73, Zack W9SZ
On Mon, Oct 18, 2021 at 3:22 PM Andrew Kurtz via groups.io <adkurtz= [email protected]> 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
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Re: "Q", Coils, toroids, and guesswork?
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¡
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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
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Re: "Q", Coils, toroids, and guesswork?
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 (1131¦¸ 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 On 10/18/2021 4:00 PM, Zack Widup wrote: The closest thing I see to that is the Amidon type J ferrite toroids. Useful frequency range is 1 to 15 MHz for type J. They don't specify a size exactly the same, but the FT87-J is the closest they have.
73, Zack W9SZ
On Mon, Oct 18, 2021 at 3:22 PM Andrew Kurtz via groups.io <adkurtz= [email protected]> 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
-- This email has been checked for viruses by Avast antivirus software.
|
Re: "Q", Coils, toroids, and guesswork?
This cannot be a powdered iron core. I do not know of any powdered iron cores that have an AL value of 50,000 uH/100T. It has to be a ferrite core.
Zack W9SZ
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On Mon, Oct 18, 2021 at 4:02 PM W0LEV <davearea51a@...> wrote: Here are sites that indicate the frequency range over which powdered iron cores are best applied, max Q. Powdered iron cores are designed for a specific frequency range to maximize the Q of inductors wound on them. They are not appropriate for common mode chokes, baluns, or wide band RF transformers. For common mode chokes, baluns, and wide band RF transformers, over HF frequencies, 31 or 43 material is best. These are true ferrites and not powdered iron cores.
The BLUE material, #1, exhibits highest Q from 0.5 to 5 MHz. Not to say it won't work over other frequencies, but the inductor Q will be compromised. For highest Q over HF frequencies, the RED cores, #2 material, is best.
Dave - W?LEV
On Mon, Oct 18, 2021 at 8:22 PM Andrew Kurtz via groups.io <adkurtz= [email protected]> 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*
|
Re: "Q", Coils, toroids, and guesswork?
On 10/18/21 1:16 PM, Andrew Kurtz via groups.io 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. Check the units of your toroid chart - not everyone used the same scale, I've seen? uH/100 turns, mH/100 turns and others as uH/turns^2 L (mH) = AL(mH/turns^2) * 36 0.180 = AL * 36? -> 0.005 mH/turns^2 or 5 uH/turns^2 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
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Re: "Q", Coils, toroids, and guesswork?
Here are sites that indicate the frequency range over which powdered iron cores are best applied, max Q. Powdered iron cores are designed for a specific frequency range to maximize the Q of inductors wound on them. They are not appropriate for common mode chokes, baluns, or wide band RF transformers. For common mode chokes, baluns, and wide band RF transformers, over HF frequencies, 31 or 43 material is best. These are true ferrites and not powdered iron cores. The BLUE material, #1, exhibits highest Q from 0.5 to 5 MHz. Not to say it won't work over other frequencies, but the inductor Q will be compromised. For highest Q over HF frequencies, the RED cores, #2 material, is best. Dave - W?LEV On Mon, Oct 18, 2021 at 8:22 PM Andrew Kurtz via groups.io <adkurtz= [email protected]> 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*
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Re: "Q", Coils, toroids, and guesswork?
The closest thing I see to that is the Amidon type J ferrite toroids. Useful frequency range is 1 to 15 MHz for type J. They don't specify a size exactly the same, but the FT87-J is the closest they have. 73, Zack W9SZ On Mon, Oct 18, 2021 at 3:22 PM Andrew Kurtz via groups.io <adkurtz= [email protected]> 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
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Re: "Q", Coils, toroids, and guesswork?
That 200 Ohms is not the same as a 200 Ohm resistor at any frequency other that 1 MHz. Again Impedance, not resistance.? Kent
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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
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