I've just taken delivery of a couple of ferrite 'binocular' choke cores;
each one came with two thinwalled metal tubes and some bits of printed circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper
areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; each one came with two thinwalled metal tubes and some bits of printed circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >> > each one came with two thinwalled metal tubes and some bits of printed
circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper
areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the
end of a tube is individually isolated but they could easily be joined
to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional
way of twisting the primary and secondary conductors together before >threading them through the core would create a capacitive imbalance. If
I use the tubes as a 1-turn secondary and thread the inner of the feed
co-ax through them, this will give much lower capacitance imbalance.
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>> > each one came with two thinwalled metal tubes and some bits of printed >>> > circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper >>> > areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the
end of a tube is individually isolated but they could easily be joined
to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>way of twisting the primary and secondary conductors together before >>threading them through the core would create a capacitive imbalance. If
I use the tubes as a 1-turn secondary and thread the inner of the feed >>co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
Liz Tuddenham wrote:
Jeroen Belleman wrote:
Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>> > each one came with two thinwalled metal tubes and some bits of printed >>> > circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper >>> > areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the
end of a tube is individually isolated but they could easily be joined
to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>way of twisting the primary and secondary conductors together before >>threading them through the core would create a capacitive imbalance. If
I use the tubes as a 1-turn secondary and thread the inner of the feed >>co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores;
each one came with two thinwalled metal tubes and some bits of printed
circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper
areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
<https://www.communication-concepts.com/content/AN762/AN762_Application_Note.pdf>
Jeroen Belleman
Joe Gwinn wrote:
Liz Tuddenham wrote:
Jeroen Belleman wrote:
Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>>> each one came with two thinwalled metal tubes and some bits of printed >>>>> circuit board. The tubes appear to go through the holes in the choke >>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the
end of a tube is individually isolated but they could easily be joined
to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>> way of twisting the primary and secondary conductors together before
threading them through the core would create a capacitive imbalance. If >>> I use the tubes as a 1-turn secondary and thread the inner of the feed
co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Thank you for all your interesting threads as of late, Liz.
It's difficult for me to follow this conversation. Maybe my followup
simply repeats what you guys already said.
The tubes are shields designed to fit inside the binocular core
holes. You then soldier them together with a PCB at each end like so:
<https://www.qsl.net/g3oou/BBTrans_4278a.jpg>
It becomes more interesting with coax:
<https://www.qsl.net/kf8od/ldmos53.jpg>
Danke,
Don wrote:
Joe Gwinn wrote:
Liz Tuddenham wrote:
Jeroen Belleman wrote:
Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>>>> each one came with two thinwalled metal tubes and some bits of printed >>>>>> circuit board. The tubes appear to go through the holes in the choke >>>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>> end of a tube is individually isolated but they could easily be joined >>>> to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>> way of twisting the primary and secondary conductors together before
threading them through the core would create a capacitive imbalance. If >>>> I use the tubes as a 1-turn secondary and thread the inner of the feed >>>> co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Thank you for all your interesting threads as of late, Liz.
It's difficult for me to follow this conversation. Maybe my followup
simply repeats what you guys already said.
The tubes are shields designed to fit inside the binocular core
holes. You then soldier them together with a PCB at each end like so:
<https://www.qsl.net/g3oou/BBTrans_4278a.jpg>
It becomes more interesting with coax:
<https://www.qsl.net/kf8od/ldmos53.jpg>
Not at both ends! That is not going to work!
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>> > each one came with two thinwalled metal tubes and some bits of printed >>>> > circuit board. The tubes appear to go through the holes in the choke >>>> > and the holes in the boards fit over the ends of the tubes, with copper >>>> > areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>end of a tube is individually isolated but they could easily be joined
to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>way of twisting the primary and secondary conductors together before >>>threading them through the core would create a capacitive imbalance. If >>>I use the tubes as a 1-turn secondary and thread the inner of the feed >>>co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI, >>2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
Jeroen Belleman wrote:
Don wrote:
It's difficult for me to follow this conversation. Maybe my followup
simply repeats what you guys already said.
The tubes are shields designed to fit inside the binocular core
holes. You then soldier them together with a PCB at each end like so:
<https://www.qsl.net/g3oou/BBTrans_4278a.jpg>
It becomes more interesting with coax:
<https://www.qsl.net/kf8od/ldmos53.jpg>
Not at both ends! That is not going to work!
What you say makes sense in retrospect.
Don wrote:
Jeroen Belleman wrote:
Don wrote:
<snip>
It's difficult for me to follow this conversation. Maybe my followup
simply repeats what you guys already said.
The tubes are shields designed to fit inside the binocular core
holes. You then soldier them together with a PCB at each end like so:
<https://www.qsl.net/g3oou/BBTrans_4278a.jpg>
It becomes more interesting with coax:
<https://www.qsl.net/kf8od/ldmos53.jpg>
Not at both ends! That is not going to work!
What you say makes sense in retrospect.
In retro-retrospect what you say doesn't make sense. Is <https://www.qsl.net/kf8od/ldmos53.jpg> wrong? It says to solder both
ends.
What flummoxes me is why shielded coax is is itself inserted into a separately shielded sleeve?
Danke,
Don wrote:
Jeroen Belleman wrote:
Don wrote:
<snip>
It's difficult for me to follow this conversation. Maybe my followup
simply repeats what you guys already said.
The tubes are shields designed to fit inside the binocular core
holes. You then soldier them together with a PCB at each end like so:
<https://www.qsl.net/g3oou/BBTrans_4278a.jpg>
It becomes more interesting with coax:
<https://www.qsl.net/kf8od/ldmos53.jpg>
Not at both ends! That is not going to work!
What you say makes sense in retrospect.
In retro-retrospect what you say doesn't make sense. Is <https://www.qsl.net/kf8od/ldmos53.jpg> wrong? It says to solder both
ends.
What flummoxes me is why shielded coax is is itself inserted into a separately shielded sleeve?
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>>> each one came with two thinwalled metal tubes and some bits of printed >>>>> circuit board. The tubes appear to go through the holes in the choke >>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the
end of a tube is individually isolated but they could easily be joined
to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>> way of twisting the primary and secondary conductors together before
threading them through the core would create a capacitive imbalance. If >>> I use the tubes as a 1-turn secondary and thread the inner of the feed
co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
On 3/20/25 16:43, john larkin wrote:
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>>>> each one came with two thinwalled metal tubes and some bits of printed >>>>>> circuit board. The tubes appear to go through the holes in the choke >>>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>> end of a tube is individually isolated but they could easily be joined >>>> to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>> way of twisting the primary and secondary conductors together before
threading them through the core would create a capacitive imbalance. If >>>> I use the tubes as a 1-turn secondary and thread the inner of the feed >>>> co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
Those are 1:1 baluns. It's not too hard to get stupendous bandwidths
with those. Six decades of frequency should be quite easy. It gets
harder when you want different impedances at the ends.
Jeroen Belleman
On Fri, 21 Mar 2025 00:08:53 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 3/20/25 16:43, john larkin wrote:
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores;
each one came with two thinwalled metal tubes and some bits of printed >>>>>>> circuit board. The tubes appear to go through the holes in the choke >>>>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single- >>>>>> turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>>> end of a tube is individually isolated but they could easily be joined >>>>> to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>>> way of twisting the primary and secondary conductors together before >>>>> threading them through the core would create a capacitive imbalance. If >>>>> I use the tubes as a 1-turn secondary and thread the inner of the feed >>>>> co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI, >>>> 2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
Those are 1:1 baluns. It's not too hard to get stupendous bandwidths
with those. Six decades of frequency should be quite easy. It gets
harder when you want different impedances at the ends.
Jeroen Belleman
I call them transformers. We use them to isolate pulse generator
outputs, and sometimes to get a voltage step-up.
On Thu, 20 Mar 2025 08:43:54 -0700, john larkin <jlArbor.com> wrote:
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>Yes, these are transmission-line baluns. The ferrite surrounding the
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>>>> each one came with two thinwalled metal tubes and some bits of printed >>>>>> circuit board. The tubes appear to go through the holes in the choke >>>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>> end of a tube is individually isolated but they could easily be joined >>>> to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>> way of twisting the primary and secondary conductors together before
threading them through the core would create a capacitive imbalance. If >>>> I use the tubes as a 1-turn secondary and thread the inner of the feed >>>> co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
coax acts as a RF choke, ensuring that center and shield currents are
equal and opposite, so external fields cancel. The ferrite can be
lossy; this actually helps, and suppresses resonances.
I dug deeply into the issue of transmission-line transformers circa
2004, and still have most of the stuff from that era, but have
forgotten many of the details. There were a number of approaches,
each with advantages and disadvantages. The recipe is in the Fibre
Channel standard, long forgotten. Fast Ethernet used the line coding
et al pioneered by Fibre Channel.
I was implementing such a transformer for use in Fibre Channel and
Ethernet compliance measurements, and ended up with insulated
semi-rigid coax hand-wound on a ferrite toroid.
Some people to search on include Sevick, Matrick, Ruthroff, and
Guanella.
A good source is Motorola AN749 Broadband Transformers.
And the Chinese have been at work. This is open-access:
He, Ding, Zhentao Yu, Jie Chen, Kaiyuan Du, Zhiqiang Zhu, Pu Cheng,
and Cheng Tan. 2024. "Modified Broadband Ruthroff-Type Transmission
Line Transformer Balun for Isolation-Enhanced Passive Mixer Design" Micromachines 15, no. 3: 332.<https://doi.org/10.3390/mi15030332>
Joe
On 3/20/25 16:43, john larkin wrote:
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>>>> each one came with two thinwalled metal tubes and some bits of printed >>>>>> circuit board. The tubes appear to go through the holes in the choke >>>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>> end of a tube is individually isolated but they could easily be joined >>>> to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>> way of twisting the primary and secondary conductors together before
threading them through the core would create a capacitive imbalance. If >>>> I use the tubes as a 1-turn secondary and thread the inner of the feed >>>> co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI,
2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
Those are 1:1 baluns. It's not too hard to get stupendous bandwidths
with those. Six decades of frequency should be quite easy. It gets
harder when you want different impedances at the ends.
Jeroen Belleman
On Wed, 19 Mar 2025 23:24:36 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>> each one came with two thinwalled metal tubes and some bits of printed
circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper
areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
<https://www.communication-concepts.com/content/AN762/AN762_Application_Note.pdf>
Jeroen Belleman
Can also be used in directional couplers and baluns, which I suppose
are just high frequency transformers by another name.
RL
Don wrote:
It looks to me that the 3 sections of coax shield are in parallel with
the
metal tubes and their opposite end shorting bar, forming the low
impedance
single turn winding, to be connected at the unshorted end with the coax shield connections, hi-Z connections to coax center conductors extending
from opposite end - 4:1 balun?
On 3/20/25 21:49, Joe Gwinn wrote:
On Thu, 20 Mar 2025 08:43:54 -0700, john larkin <jlArbor.com> wrote:
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>Yes, these are transmission-line baluns. The ferrite surrounding the
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores;
each one came with two thinwalled metal tubes and some bits of printed >>>>>>> circuit board. The tubes appear to go through the holes in the choke >>>>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single- >>>>>> turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>>> end of a tube is individually isolated but they could easily be joined >>>>> to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>>> way of twisting the primary and secondary conductors together before >>>>> threading them through the core would create a capacitive imbalance. If >>>>> I use the tubes as a 1-turn secondary and thread the inner of the feed >>>>> co-ax through them, this will give much lower capacitance imbalance.
This also sounds like it could be a transmission-line transformer;
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name.
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI, >>>> 2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
coax acts as a RF choke, ensuring that center and shield currents are
equal and opposite, so external fields cancel. The ferrite can be
lossy; this actually helps, and suppresses resonances.
I dug deeply into the issue of transmission-line transformers circa
2004, and still have most of the stuff from that era, but have
forgotten many of the details. There were a number of approaches,
each with advantages and disadvantages. The recipe is in the Fibre
Channel standard, long forgotten. Fast Ethernet used the line coding
et al pioneered by Fibre Channel.
I was implementing such a transformer for use in Fibre Channel and
Ethernet compliance measurements, and ended up with insulated
semi-rigid coax hand-wound on a ferrite toroid.
Some people to search on include Sevick, Matrick, Ruthroff, and
Guanella.
Who is MatricK? Link? Would that be about *matrix* transformers?
A good source is Motorola AN749 Broadband Transformers.
Ah, Helge Granberg again. A good one.
And the Chinese have been at work. This is open-access:
He, Ding, Zhentao Yu, Jie Chen, Kaiyuan Du, Zhiqiang Zhu, Pu Cheng,
and Cheng Tan. 2024. "Modified Broadband Ruthroff-Type Transmission
Line Transformer Balun for Isolation-Enhanced Passive Mixer Design"
Micromachines 15, no. 3: 332.<https://doi.org/10.3390/mi15030332>
Joe
When I see '?/4' in a transformer description, I lose interest.
On Thu, 20 Mar 2025 12:39:43 -0400, legg <legg@nospam.magma.ca> wrote:
On Wed, 19 Mar 2025 23:24:36 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>> each one came with two thinwalled metal tubes and some bits of printed >>>> circuit board. The tubes appear to go through the holes in the choke
and the holes in the boards fit over the ends of the tubes, with copper >>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
<https://www.communication-concepts.com/content/AN762/AN762_Application_Note.pdf>
Jeroen Belleman
Can also be used in directional couplers and baluns, which I suppose
are just high frequency transformers by another name.
RL
Some people enjoy calling txline transformers "ununs" when neither end
is a balanced load against ground.
Is there a balbal?
On Fri, 21 Mar 2025 00:16:33 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 3/20/25 21:49, Joe Gwinn wrote:
On Thu, 20 Mar 2025 08:43:54 -0700, john larkin <jlArbor.com> wrote:
On Thu, 20 Mar 2025 10:49:08 -0400, Joe Gwinn <joegwinn@comcast.net>Yes, these are transmission-line baluns. The ferrite surrounding the
wrote:
On Thu, 20 Mar 2025 07:30:58 +0000, liz@poppyrecords.invalid.invalid >>>>> (Liz Tuddenham) wrote:
Jeroen Belleman <jeroen@nospam.please> wrote:This also sounds like it could be a transmission-line transformer;
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores;
each one came with two thinwalled metal tubes and some bits of printed >>>>>>>> circuit board. The tubes appear to go through the holes in the choke >>>>>>>> and the holes in the boards fit over the ends of the tubes, with copper
areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single- >>>>>>> turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
That's the sort of thing I suspected. Each square pad surrounding the >>>>>> end of a tube is individually isolated but they could easily be joined >>>>>> to make a loop circuit with some wire straps.
I intend using this as a 1:1 balun and was worried that the conventional >>>>>> way of twisting the primary and secondary conductors together before >>>>>> threading them through the core would create a capacitive imbalance. If >>>>>> I use the tubes as a 1-turn secondary and thread the inner of the feed >>>>>> co-ax through them, this will give much lower capacitance imbalance. >>>>>
these are very wideband. The ferrite cores serve as RF chokes,
ensuring the shield and center currents are exactly equal and
opposite. It is _not_ an ordinary RF transformer, despite the name. >>>>>
"Transmission Line Transformers", Fourth Edition, Jerry Sevick, W2FMI, >>>>> 2001, 289 pages, ISBN 1-884932-18-5, TK6565.T7 S48 2001,
621.384'11--dc21.
Joe
I have the Sevick book but it's not very useful.
We make super wideband tline transformers from micro-coax and pot
cores.
https://www.dropbox.com/scl/fi/32s2rfcu4q4iq6l6v1eb4/Pot_Core_TXline.JPG?rlkey=6k7xusurck0jf1ky9n6ja2ebz&raw=1
https://www.dropbox.com/scl/fi/adcocf1rb7lnanj7zo9xp/TX_1.jpg?rlkey=m7prsxj94fa57ynqoep0ydgnl&raw=1
Or toroids, which are harder to make.
https://www.dropbox.com/scl/fi/xuqjzt3h1oq7uexwiu6c8/T750_1.JPG?rlkey=si165mntuu0h40zgsbi0qzxj7&raw=1
coax acts as a RF choke, ensuring that center and shield currents are
equal and opposite, so external fields cancel. The ferrite can be
lossy; this actually helps, and suppresses resonances.
I dug deeply into the issue of transmission-line transformers circa
2004, and still have most of the stuff from that era, but have
forgotten many of the details. There were a number of approaches,
each with advantages and disadvantages. The recipe is in the Fibre
Channel standard, long forgotten. Fast Ethernet used the line coding
et al pioneered by Fibre Channel.
I was implementing such a transformer for use in Fibre Channel and
Ethernet compliance measurements, and ended up with insulated
semi-rigid coax hand-wound on a ferrite toroid.
Some people to search on include Sevick, Matrick, Ruthroff, and
Guanella.
Who is MatricK? Link? Would that be about *matrix* transformers?
No, it's a man's name. The letter "r" is a typo.
RICHARD E. MATICK
Transmission Line Pulse Transformers-
Theory and Applications
PROCEEDINGS OF THE IEEE, VOL. 56, NO. 1, JANUARY 1968
A good source is Motorola AN749 Broadband Transformers.
Ah, Helge Granberg again. A good one.
Yes. AN762 on Linear Amplifiers was mentioned elsewhere in this
thread.
And the Chinese have been at work. This is open-access:
He, Ding, Zhentao Yu, Jie Chen, Kaiyuan Du, Zhiqiang Zhu, Pu Cheng,
and Cheng Tan. 2024. "Modified Broadband Ruthroff-Type Transmission
Line Transformer Balun for Isolation-Enhanced Passive Mixer Design"
Micromachines 15, no. 3: 332.<https://doi.org/10.3390/mi15030332>
Joe
When I see '?/4' in a transformer description, I lose interest.
That seems awfully strict for non-native speakers of English. Such a
rule would pretty much cripple SED. And the ? mark could well be a
typo.
Joe
Glen Walpert wrote:
Don wrote:
<snip>
It looks to me that the 3 sections of coax shield are in parallel with
the metal tubes and their opposite end shorting bar, forming the low
impedance single turn winding, to be connected at the unshorted end
with the coax shield connections, hi-Z connections to coax center
conductors extending from opposite end - 4:1 balun?
<https://www.qsl.net/kf8od/ldmos1.html> offers a more fleshed out
circuit description. The designer designates the device a 4:1 "very
broadband transformer."
<https://www.qsl.net/kf8od/ldmos34.jpg> shows the schematic. In the
amp as assembled, the transformer output's oriented on the bottom: <https://www.qsl.net/kf8od/ldmos50.jpg>. Everything about its output
makes perfect sense to me. The transformer's twin tubular primary inputs shown at the latter link also makes perfect sense to me.
A center tap for the transformer's the thing missing from my mind's
eye. Perhaps the shield of the coax cryptically connects the center tap?
Danke,
john larkin <jlArbor.com> wrote:
On Thu, 20 Mar 2025 12:39:43 -0400, legg <legg@nospam.magma.ca> wrote:
On Wed, 19 Mar 2025 23:24:36 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 3/19/25 22:40, Liz Tuddenham wrote:
I've just taken delivery of a couple of ferrite 'binocular' choke cores; >>>>> each one came with two thinwalled metal tubes and some bits of printed >>>>> circuit board. The tubes appear to go through the holes in the choke >>>>> and the holes in the boards fit over the ends of the tubes, with copper >>>>> areas that could possibly be soldered to them.
Does anyone know what purpose these serve?
This sounds very much like the transformers used in wideband RF
power amplifiers. See for example Helge Granberg's application
note 762. The tubes with a piece of circuit board form the single-
turn low impedance winding, and a number of turns of insulated
copper wire going through the tubes form the high-impedance
winding. This makes for a good coupling factor and consequently
good wideband operation.
<https://www.communication-concepts.com/content/AN762/AN762_Application_Note.pdf>
Jeroen Belleman
Can also be used in directional couplers and baluns, which I suppose
are just high frequency transformers by another name.
RL
Some people enjoy calling txline transformers "ununs" when neither end
is a balanced load against ground.
Is there a balbal?
Its a tree, like a baobab with pompoms
Don wrote:
Glen Walpert wrote:
Don wrote:
<snip>
It looks to me that the 3 sections of coax shield are in parallel with
the metal tubes and their opposite end shorting bar, forming the low
impedance single turn winding, to be connected at the unshorted end
with the coax shield connections, hi-Z connections to coax center
conductors extending from opposite end - 4:1 balun?
<https://www.qsl.net/kf8od/ldmos1.html> offers a more fleshed out
circuit description. The designer designates the device a 4:1 "very
broadband transformer."
<https://www.qsl.net/kf8od/ldmos34.jpg> shows the schematic. In the
amp as assembled, the transformer output's oriented on the bottom:
<https://www.qsl.net/kf8od/ldmos50.jpg>. Everything about its output
makes perfect sense to me. The transformer's twin tubular primary inputs
shown at the latter link also makes perfect sense to me.
A center tap for the transformer's the thing missing from my mind's
eye. Perhaps the shield of the coax cryptically connects the center tap?
Thanks, that clarifies things. A bit tough to see in the assembly photo,
but the center tap on the single turn primary is the shorting bar between
the two metal tubes on the same end as the coax inner conductor
connections. I suppose the two 1/2 turn primary windings contribute independently to the 4 turn output to provide the stated 1:16 ratio.
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