Topics

Small ferrite cores

Andy G4JNT
 

Looking for a supplier of small, 2mm diameter or so, ferrite toroids suitable for 1 - 1000MHz - (not all that at the same time!).  They are intended as baluns at the output of RF quad downconverter chips that typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher than 50 ohms

In the past I've dismantled Mini-Circuits splitters and things to get such toroids, but stocks of MC components I'm prepared to break up is getting low.  And for reproducible / publishable designs a purchasable solution is needed.

Anyone know of companies with good stocks of these.
No Chinese or dubious Ebay suppliers, just proven reputable organisations pse.



Gareth G4SDW (ne G8DXY) GQRP #3339
 

On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:


Looking for a supplier of small, 2mm diameter or so, ferrite toroids
suitable for 1 - 1000MHz - (not all that at the same time!). They are
intended as baluns at the output of RF quad downconverter chips that
typically have I+ / I- and Q+ / Q- outputs at an impedance rather higher
than 50 ohms

In the past I've dismantled Mini-Circuits splitters and things to get such
toroids, but stocks of MC components I'm prepared to break up is getting
low. And for reproducible / publishable designs a purchasable solution is
needed.

One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7 left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!! :-)

Andy G4JNT
 

I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)




Ian White
 

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:

I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)




John Rabson
 

I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF

On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)





Andy G4JNT
 

They're something like 8mm square.   Three times the size of the IC I want to match to.
Must go through the FairRite spec sheets and select the right material then find suitable supplier.

I'd love to know the details of the four or so toroids salvaged from a MiniCircuits splitter rated 1 - 1000MHz.  I used those cores to make a balun for an AD9852 DDS and it was practically flat from 300kHz to 120MHz



On Thu, 19 Sep 2019 at 15:51, John Rabson <john.rabson07@...> wrote:
I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF
On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)





Peter Chadwick
 

Andy,


Have a look at EPCOS - TDK. They have binocular cores down to 1.4 by 3.6 mm, in material for use in broadband transformers up to 150MHz.


https://www.tdk-electronics.tdk.com/en/529426/products/product-catalog/ferrites-and-accessories/epcos-ferrites-and-accessories/ring-double-aperture-cores


vy 73


Peter G3RZP



------ Original Message ------
From: "Andy TALBOT" <andy.g4jnt@...>
To: RSGB-Workshop@groups.io
Sent: Thursday, 19 Sep, 19 At 16:02
Subject: Re: [RSGB-Workshop] Small ferrite cores

They're something like 8mm square. Three times the size of the IC I want to match to.
Must go through the FairRite spec sheets and select the right material then find suitable supplier.

I'd love to know the details of the four or so toroids salvaged from a MiniCircuits splitter rated 1 - 1000MHz. I used those cores to make a balun for an AD9852 DDS and it was practically flat from 300kHz to 120MHz



On Thu, 19 Sep 2019 at 15:51, John Rabson <john.rabson07@...> wrote:
I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF
On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism. If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!). They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I- and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low. And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7 left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!! :-)





Peter Chadwick
 

Sorry, should read 'up to 250MHz...


Fat fingers!


vy 73


Peter G3RZP



------ Original Message ------
From: "Peter Chadwick via Groups.Io" <g8on@...>
To: RSGB-Workshop@groups.io
Sent: Thursday, 19 Sep, 19 At 16:18
Subject: Re: [RSGB-Workshop] Small ferrite cores

Andy,


Have a look at EPCOS - TDK. They have binocular cores down to 1.4 by 3.6 mm, in material for use in broadband transformers up to 150MHz.


https://www.tdk-electronics.tdk.com/en/529426/products/product-catalog/ferrites-and-accessories/epcos-ferrites-and-accessories/ring-double-aperture-cores


vy 73


Peter G3RZP



------ Original Message ------
From: "Andy TALBOT" <andy.g4jnt@...>
To: RSGB-Workshop@groups.io
Sent: Thursday, 19 Sep, 19 At 16:02
Subject: Re: [RSGB-Workshop] Small ferrite cores

They're something like 8mm square. Three times the size of the IC I want to match to.
Must go through the FairRite spec sheets and select the right material then find suitable supplier.

I'd love to know the details of the four or so toroids salvaged from a MiniCircuits splitter rated 1 - 1000MHz. I used those cores to make a balun for an AD9852 DDS and it was practically flat from 300kHz to 120MHz



On Thu, 19 Sep 2019 at 15:51, John Rabson <john.rabson07@...> wrote:
I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF
On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism. If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!). They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I- and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low. And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7 left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!! :-)





G8HUL
 

Hi Andy

RS god a good range of Epcos (Siemens as was) toroids and 2 hole cores.

73
Jeff G8HUL

-----Original Message-----
From: RSGB-Workshop@groups.io <RSGB-Workshop@groups.io> On Behalf Of Andy TALBOT
Sent: 19 September 2019 13:38
To: RSGB-Workshop@groups.io
Subject: [RSGB-Workshop] Small ferrite cores

Looking for a supplier of small, 2mm diameter or so, ferrite toroids suitable for 1 - 1000MHz - (not all that at the same time!). They are intended as baluns at the output of RF quad downconverter chips that typically have I+ / I- and Q+ / Q- outputs at an impedance rather higher than 50 ohms

In the past I've dismantled Mini-Circuits splitters and things to get such toroids, but stocks of MC components I'm prepared to break up is getting low. And for reproducible / publishable designs a purchasable solution is needed.

Anyone know of companies with good stocks of these.
No Chinese or dubious Ebay suppliers, just proven reputable organisations pse.



Andy
www.g4jnt.com <http://www.g4jnt.com>

Paul Randall G3NJV
 

Andy, are you actually wanting to magnetise the core? I thought more or less all transformers for that sort of frequency range would be balanced bifilar or trifilar windings in transmission line format and the core material would be relatively unimportant as it's job is primarily to stop common mode current.

I may have this totally wrong and if so would like to learn more. 

I remember making a pair of 4:1 baluns with close twisted bifilar windings on 50mm of old medium wave ferrite rod. Back to back @ 100Watts they gave perfect match, no detectable heating and immeasurably small loss 160 thru 10m. I always ascribed this to the winding method,  not the core. 

Best regards Paul G3NJV



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Andy TALBOT <andy.g4jnt@...>
Date: 19/09/2019 16:02 (GMT+00:00)
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Small ferrite cores

They're something like 8mm square.   Three times the size of the IC I want to match to.
Must go through the FairRite spec sheets and select the right material then find suitable supplier.

I'd love to know the details of the four or so toroids salvaged from a MiniCircuits splitter rated 1 - 1000MHz.  I used those cores to make a balun for an AD9852 DDS and it was practically flat from 300kHz to 120MHz



On Thu, 19 Sep 2019 at 15:51, John Rabson <john.rabson07@...> wrote:
I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF
On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)





Andy G4JNT
 

SPOT ON!
It's to make baluns & matching transformers for frequencies, typically in the range 1 - 1000MHz.    So, yes,  99% of the time they will be made with multi-filar windings and the core just just has to give common mode impedance.

But that 1% of the time, it's possible a true transformer action will be called for, so control over what sort of ferrite is used  ...



On Thu, 19 Sep 2019 at 19:46, Paul Randall <paulfrandall@...> wrote:
Andy, are you actually wanting to magnetise the core? I thought more or less all transformers for that sort of frequency range would be balanced bifilar or trifilar windings in transmission line format and the core material would be relatively unimportant as it's job is primarily to stop common mode current.

I may have this totally wrong and if so would like to learn more. 

I remember making a pair of 4:1 baluns with close twisted bifilar windings on 50mm of old medium wave ferrite rod. Back to back @ 100Watts they gave perfect match, no detectable heating and immeasurably small loss 160 thru 10m. I always ascribed this to the winding method,  not the core. 

Best regards Paul G3NJV



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Andy TALBOT <andy.g4jnt@...>
Date: 19/09/2019 16:02 (GMT+00:00)
Subject: Re: [RSGB-Workshop] Small ferrite cores

They're something like 8mm square.   Three times the size of the IC I want to match to.
Must go through the FairRite spec sheets and select the right material then find suitable supplier.

I'd love to know the details of the four or so toroids salvaged from a MiniCircuits splitter rated 1 - 1000MHz.  I used those cores to make a balun for an AD9852 DDS and it was practically flat from 300kHz to 120MHz



On Thu, 19 Sep 2019 at 15:51, John Rabson <john.rabson07@...> wrote:
I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF
On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)





Gareth G4SDW (ne G8DXY) GQRP #3339
 

On Thu, Sep 19, 2019 at 03:04 PM, Andy TALBOT wrote:


I rather suspect those core types are the complete diametric opposite of
what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop
in order to keep the residual magnetism. If a ferrite with a large H-loop
is used at RF, all the energy is absorbed taking B around the loop every
cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at
lower frequencies, so conducted RF gets absorbed
Aaaah, interesting.

So, everyone, were one to encounter an unknown ferrite, how woould one measure its
characteristics as suitable either for EMC suppression (big hystersis loop)
or for RF use?

Andy G4JNT
 

First thing to do is to measure the Al , or specific inductance, nH/turn^2, by winding a few turns on and using an LC meter or whatever you have. Ideally at a range of frequencies
Then look at ferrite tables to see what has a similar Al and what frequency range it suggests
Then make a 1:1 transformer using sufficient turns in a 50 ohms system
Measure loss
If it looks good, try putting a few watts through, always observing the Vrms = 4.44.F.N.A.B limit
If it works and stays cool then it's a good RF ferrite

That's what I do, anyway



On Thu, 19 Sep 2019 at 20:27, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 03:04 PM, Andy TALBOT wrote:

Aaaah, interesting.

So, everyone, were one to encounter an unknown ferrite, how woould one measure its
characteristics as suitable either for EMC suppression (big hystersis loop)
or for RF use?

Paul Randall G3NJV
 

Andy, Phew,  thanks for that.  Did a quick look around for you with goggle.  Found this.  Interesting because they used .... guess what? ....1mm old memory cores!

Https://digitalcommons.calpoly.edu/cgi/viewcontent.cgi?article=1282&context=eesp

Best regards Paul G3NJV




Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Andy TALBOT <andy.g4jnt@...>
Date: 19/09/2019 20:02 (GMT+00:00)
To: RSGB-Workshop@groups.io
Subject: Re: [RSGB-Workshop] Small ferrite cores

SPOT ON!
It's to make baluns & matching transformers for frequencies, typically in the range 1 - 1000MHz.    So, yes,  99% of the time they will be made with multi-filar windings and the core just just has to give common mode impedance.

But that 1% of the time, it's possible a true transformer action will be called for, so control over what sort of ferrite is used  ...



On Thu, 19 Sep 2019 at 19:46, Paul Randall <paulfrandall@...> wrote:
Andy, are you actually wanting to magnetise the core? I thought more or less all transformers for that sort of frequency range would be balanced bifilar or trifilar windings in transmission line format and the core material would be relatively unimportant as it's job is primarily to stop common mode current.

I may have this totally wrong and if so would like to learn more. 

I remember making a pair of 4:1 baluns with close twisted bifilar windings on 50mm of old medium wave ferrite rod. Back to back @ 100Watts they gave perfect match, no detectable heating and immeasurably small loss 160 thru 10m. I always ascribed this to the winding method,  not the core. 

Best regards Paul G3NJV



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Andy TALBOT <andy.g4jnt@...>
Date: 19/09/2019 16:02 (GMT+00:00)
Subject: Re: [RSGB-Workshop] Small ferrite cores

They're something like 8mm square.   Three times the size of the IC I want to match to.
Must go through the FairRite spec sheets and select the right material then find suitable supplier.

I'd love to know the details of the four or so toroids salvaged from a MiniCircuits splitter rated 1 - 1000MHz.  I used those cores to make a balun for an AD9852 DDS and it was practically flat from 300kHz to 120MHz



On Thu, 19 Sep 2019 at 15:51, John Rabson <john.rabson07@...> wrote:
I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF
On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)





Andy G4JNT
 

I only skimmed the article, but they admit that other than for the Guanella balun, results were poor.     
With decent ferrite material,   Epcos (Siemens) N30 and K1 for example, transformer balun action can be very low loss, when the appropriate ferrite is used for the frequency.
Actually, for Guanella baluns, where all the core is doing is providing common mode impedance, I suspect old core-store types may be OK for high frequencies and low power



On Thu, 19 Sep 2019 at 21:36, Paul Randall <paulfrandall@...> wrote:
Andy, Phew,  thanks for that.  Did a quick look around for you with goggle.  Found this.  Interesting because they used .... guess what? ....1mm old memory cores!


Best regards Paul G3NJV




Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Andy TALBOT <andy.g4jnt@...>
Date: 19/09/2019 20:02 (GMT+00:00)
Subject: Re: [RSGB-Workshop] Small ferrite cores

SPOT ON!
It's to make baluns & matching transformers for frequencies, typically in the range 1 - 1000MHz.    So, yes,  99% of the time they will be made with multi-filar windings and the core just just has to give common mode impedance.

But that 1% of the time, it's possible a true transformer action will be called for, so control over what sort of ferrite is used  ...



On Thu, 19 Sep 2019 at 19:46, Paul Randall <paulfrandall@...> wrote:
Andy, are you actually wanting to magnetise the core? I thought more or less all transformers for that sort of frequency range would be balanced bifilar or trifilar windings in transmission line format and the core material would be relatively unimportant as it's job is primarily to stop common mode current.

I may have this totally wrong and if so would like to learn more. 

I remember making a pair of 4:1 baluns with close twisted bifilar windings on 50mm of old medium wave ferrite rod. Back to back @ 100Watts they gave perfect match, no detectable heating and immeasurably small loss 160 thru 10m. I always ascribed this to the winding method,  not the core. 

Best regards Paul G3NJV



Sent from my Samsung Galaxy smartphone.


-------- Original message --------
From: Andy TALBOT <andy.g4jnt@...>
Date: 19/09/2019 16:02 (GMT+00:00)
Subject: Re: [RSGB-Workshop] Small ferrite cores

They're something like 8mm square.   Three times the size of the IC I want to match to.
Must go through the FairRite spec sheets and select the right material then find suitable supplier.

I'd love to know the details of the four or so toroids salvaged from a MiniCircuits splitter rated 1 - 1000MHz.  I used those cores to make a balun for an AD9852 DDS and it was practically flat from 300kHz to 120MHz



On Thu, 19 Sep 2019 at 15:51, John Rabson <john.rabson07@...> wrote:
I remember using the FX2249 binocular cores, but they weren't that little.

John F5VLF
On 19 Sep 2019, at 16:44, Ian White <gm3sek@...> wrote:

The tiny Siemens binocular cores used to be very popular for RF transformers and baluns. I believe Fair-Rite also supply these in LF grades of ferrite.

73 from Ian GM3SEK

On 19/09/2019 15:04, Andy TALBOT wrote:
I rather suspect those core types are the complete diametric opposite of what one would use for an RF transformer.
To work as a memory, the ferrite would have to have a large hysteresis loop in order to keep the residual magnetism.  If a ferrite with a large H-loop is used at RF, all the energy is absorbed taking B around the loop every cycle, dissipating the resulting energy as heat.

Just, in fact, what you want in ferrites designed for EMC suppression at lower frequencies, so conducted RF gets absorbed




On Thu, 19 Sep 2019 at 13:56, Gareth G4SDW (ne G8DXY) GQRP #3339 via Groups.Io <headstone255=yahoo.com@groups.io> wrote:
On Thu, Sep 19, 2019 at 01:38 PM, Andy TALBOT wrote:

>
> Looking for a supplier of small, 2mm diameter or so, ferrite toroids
> suitable for 1 - 1000MHz - (not all that at the same time!).  They are
> intended as baluns at the output of RF quad downconverter chips that
> typically have I+ / I-  and Q+ / Q- outputs at an impedance rather higher
> than 50 ohms
>
> In the past I've dismantled Mini-Circuits splitters and things to get such
> toroids, but stocks of MC components I'm prepared to break up is getting
> low.  And for reproducible / publishable designs a purchasable solution is
> needed.


One thing that springs to mind for cores of that size is core memory planes
from (very) old computers.

"very" because later ones were too small, but I have 7  left some from a
Marconi Leo (used to have 96!) which I acquired in 1973 for my first
venture into home brewed computing; no, not with a microprocessor,
but a handful of original (not LS or Schottky) TTL and own
instruction set.

The things we radio hams widen our interest into!!!   :-)





Paul Randall G3NJV
 

The paper did not explicitly detail how anything was wound so there is uncertainty of the method.

It was amusing that it just popped up using ancient memory cores - chances of that?

I'm sure you already know about the Coilcraft PWB and WBC series?

https://www.coilcraft.com/pwb.cfm
https://www.coilcraft.com/wbc.cfm

Regards Paul