My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Someone suggested a bump in the top cover, like old muscle cars had
for carburetors.
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Someone suggested a bump in the top cover, like old muscle cars had
for carburetors.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
On 2026-01-21 11:45, john larkin wrote:>
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Yeah, putting the copper under much tension isn't a growth strategy.
Stress due to bending is quadratic in the curvature, so a little bit is
no problem, but how much is OK, I don't know.
IBM's famed Thermal Conduction Modules (TCMs) originally used sintered >alumina/refractory metal bricks (dim memory says niobium) holding either
100 or 121 flip chips.
They were brutally reliable--not a single field failure in 30 years--but
had a dielectric constant of almost 10, so they were slow.
The packaging folks at Yorktown and East Fishkill came up with a faster >technology based on copper metal and glass-ceramic bricks with an
epsilon of 5. That sped things up by 40%, which was a win as far as it >went. Trouble was, they were hopelessly unreliable.
In the original model, the metal had a lower CTE than the ceramic, so
that once the brick cooled from red heat, the metal was always in >compression, which prevented cracks from propagating. However, copper
has a higher CTE than glass ceramic, so that the copper was always in >tension. That's for a good time, not a long time.
A pal of mine figured out a fix that my caveman side found very
appealing: they dunked the hot substrates in oil, and the resulting
thermal shock cracked all the copper loose from the glass, relieving the >stress. That got them back to nearly perfect reliability.
(Later they went to copper/polyimide, I think.)
Someone suggested a bump in the top cover, like old muscle cars had
for carburetors.
Nowadays people just cut holes in the hood. ;)
Cheers
Phil Hobbs
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>> the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to >>> be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings?
A piece of coax wound on a ferrite core is basically a balun.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Jeroen Belleman
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>> cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>> are another version of the same idea, and the cores that are designed to >>>> be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings?
A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Jeroen Belleman
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>> are another version of the same idea, and the cores that are designed to >>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings?
A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Jeroen Belleman
Coax has continuous capacitance from shield (primary) to center >>(secondary). And shield-shield on the neaby windings.
The coax wound on the pot core is unbalanced to unbalanced, but in an
odd way -- shield and center are decoupled from one another, and so
one can reverse role of center and shield.
The capacitance between the outsides of the shields is irrelevant so
long as the shields are thick enough and the frequency is high enough
that the inside currents are independent of the outside surface
currents.; this takes a few megahertz to accomplish in solid copper
shields.
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>> cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>> are another version of the same idea, and the cores that are designed to >>>> be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings?
A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>> cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>> are another version of the same idea, and the cores that are designed to >>>> be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings?
A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>> are another version of the same idea, and the cores that are designed to >>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings?
A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Jeroen Belleman
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
The coax wound on the pot core is unbalanced to unbalanced, but in an
odd way -- shield and center are decoupled from one another, and so
one can reverse role of center and shield.
The capacitance between the outsides of the shields is irrelevant so
long as the shields are thick enough and the frequency is high enough
that the inside currents are independent of the outside surface
currents.; this takes a few megahertz to accomplish in solid copper
shields.
Joe
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
On 22/01/2026 11:34 am, john larkin wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>> are another version of the same idea, and the cores that are designed to >>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings?
A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
Semi-rigid coax does. Regular coax - with a braid outer conductor - has >around 95% shieding.
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Whoever mounted those pot core pair without lining up the gaps threw
away some of the energy storage you claim to be interested in.
On 1/22/26 01:48, Joe Gwinn wrote:
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>> are another version of the same idea, and the cores that are designed to >>>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>>
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Jeroen Belleman
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
The coax wound on the pot core is unbalanced to unbalanced, but in an
odd way -- shield and center are decoupled from one another, and so
one can reverse role of center and shield.
The capacitance between the outsides of the shields is irrelevant so
long as the shields are thick enough and the frequency is high enough
that the inside currents are independent of the outside surface
currents.; this takes a few megahertz to accomplish in solid copper
shields.
Joe
I differ. The purpose of winding a coax on a magnetic core is to
insulate the ends from each other by the common mode inductance
of the winding, This lends you the freedom to choose different
RF GND points at both ends.
Even though we call these things baluns, it does not necessarily
transform only from balanced to unbalanced. It can as easily
altogether invert a signal, just by choosing the right RF GND
point. Interwinding capacitance shunts the common mode inductance
of the winding, deteriorating the insulation between the ends.
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>> the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to >>> be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
The speed of electromagnet propagation is lower in Kapton that it is >dielectrics like teflon and polyethylene, which have lower dielectric >constants, but your Kapton flex probably wasn't designed to be a planar >transmission line.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its
precise distribution. If you could find a wider, flatter ferrite core
you should be able to store more energy in the same vertical headroom.
On Wed, 21 Jan 2026 08:45:53 -0800, john larkin <jl@glen--canyon.com>
wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
Toss the double pcb layers.
RL
On Thu, 22 Jan 2026 13:17:29 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/22/26 01:48, Joe Gwinn wrote:
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the >>>> same thing.
When people say "balun" they don't always mean balanced-to-unbalanced. >>>>
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Jeroen Belleman
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
The coax wound on the pot core is unbalanced to unbalanced, but in an
odd way -- shield and center are decoupled from one another, and so
one can reverse role of center and shield.
The capacitance between the outsides of the shields is irrelevant so
long as the shields are thick enough and the frequency is high enough
that the inside currents are independent of the outside surface
currents.; this takes a few megahertz to accomplish in solid copper
shields.
Joe
I differ. The purpose of winding a coax on a magnetic core is to
insulate the ends from each other by the common mode inductance
of the winding, This lends you the freedom to choose different
RF GND points at both ends.
Even though we call these things baluns, it does not necessarily
transform only from balanced to unbalanced. It can as easily
altogether invert a signal, just by choosing the right RF GND
point. Interwinding capacitance shunts the common mode inductance
of the winding, deteriorating the insulation between the ends.
I don't think we are saying contradictory things. But the viewpoint
and wording do differ.
Joe
On Thu, 22 Jan 2026 12:47:35 -0500, Joe Gwinn <joegwinn@comcast.net>
wrote:
On Thu, 22 Jan 2026 13:17:29 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/22/26 01:48, Joe Gwinn wrote:
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>>
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>> energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the >>>>> same thing.
When people say "balun" they don't always mean balanced-to-unbalanced. >>>>>
You
*don't* want capacitive coupling between the ends. That would mess >>>>>> up the principal virtue of a balun.
Jeroen Belleman
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
The coax wound on the pot core is unbalanced to unbalanced, but in an
odd way -- shield and center are decoupled from one another, and so
one can reverse role of center and shield.
The capacitance between the outsides of the shields is irrelevant so
long as the shields are thick enough and the frequency is high enough
that the inside currents are independent of the outside surface
currents.; this takes a few megahertz to accomplish in solid copper
shields.
Joe
I differ. The purpose of winding a coax on a magnetic core is to
insulate the ends from each other by the common mode inductance
of the winding, This lends you the freedom to choose different
RF GND points at both ends.
Even though we call these things baluns, it does not necessarily
transform only from balanced to unbalanced. It can as easily
altogether invert a signal, just by choosing the right RF GND
point. Interwinding capacitance shunts the common mode inductance
of the winding, deteriorating the insulation between the ends.
I don't think we are saying contradictory things. But the viewpoint
and wording do differ.
Joe
Follow-on thought: While it's true that the outer side of shield in a
coil has inductance and capacitance. The geometry is too complicated
for easy manual solution, but doesn't seem to be causing much trouble.
Joe
On Thu, 22 Jan 2026 17:57:24 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 11:34 am, john larkin wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>> are another version of the same idea, and the cores that are designed to >>>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>>
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the
same thing.
When people say "balun" they don't always mean balanced-to-unbalanced.
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
Semi-rigid coax does. Regular coax - with a braid outer conductor - has
around 95% shieding.
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Whoever mounted those pot core pair without lining up the gaps threw
away some of the energy storage you claim to be interested in.
True. The product works fine in production, but the misalignment might
matter a bit in my new GaN pulser. We'll experiment and see how much.
That pic is from the isolated HV option of a digital delay generator:
https://highlandtechnology.com/Product/P500
which, of course, I designed entirely by ignorant fooling around.
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote:
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>> cover and the PCB flex a bit - but mechanical people don't seem to
like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>> are another version of the same idea, and the cores that are designed to >>>> be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
The speed of electromagnet propagation is lower in Kapton that it is
dielectrics like teflon and polyethylene, which have lower dielectric
constants, but your Kapton flex probably wasn't designed to be a planar
transmission line.
We made several and we sure intended them to be txline windings.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll
go with connectorized coax. That is known to work.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its
precise distribution. If you could find a wider, flatter ferrite core
you should be able to store more energy in the same vertical headroom.
We are tight on PCB area, and we need to move on with the project. We
can experiment with different ferrite materials once the boards are
built. There's lots available in this pot core size.
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the
volt-seconds possible, so the pot core has to be big and barely fit in >>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>> are another version of the same idea, and the cores that are designed to >>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>
The speed of electromagnet propagation is lower in Kapton that it is
dielectrics like teflon and polyethylene, which have lower dielectric
constants, but your Kapton flex probably wasn't designed to be a planar
transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll
go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its
precise distribution. If you could find a wider, flatter ferrite core
you should be able to store more energy in the same vertical headroom.
We are tight on PCB area, and we need to move on with the project. We
can experiment with different ferrite materials once the boards are
built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so >that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that >Nickel-Zinc ferrites would work better you'd be confined to a smaller
range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote:
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence >that you and your production staff don't know enough about what you are >doing.
Performance is what really matters, but getting stuff to look right is
also important.
On 23/01/2026 3:31 am, john larkin wrote:
On Thu, 22 Jan 2026 17:57:24 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 11:34 am, john larkin wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the >>>> same thing.
When people say "balun" they don't always mean balanced-to-unbalanced. >>>>
You
*don't* want capacitive coupling between the ends. That would mess
up the principal virtue of a balun.
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
Semi-rigid coax does. Regular coax - with a braid outer conductor - has
around 95% shieding.
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Whoever mounted those pot core pair without lining up the gaps threw
away some of the energy storage you claim to be interested in.
True. The product works fine in production, but the misalignment might
matter a bit in my new GaN pulser. We'll experiment and see how much.
Of course it works adequately in production. The misalignment is only
going to create a small negative effect, but it is a very obvious
failure in quality control.
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>> are another version of the same idea, and the cores that are designed to >>>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>>
The speed of electromagnet propagation is lower in Kapton that it is
dielectrics like teflon and polyethylene, which have lower dielectric
constants, but your Kapton flex probably wasn't designed to be a planar >>>> transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll
go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its
precise distribution. If you could find a wider, flatter ferrite core
you should be able to store more energy in the same vertical headroom.
We are tight on PCB area, and we need to move on with the project. We
can experiment with different ferrite materials once the boards are
built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so
that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that
Nickel-Zinc ferrites would work better you'd be confined to a smaller
range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On Fri, 23 Jan 2026 16:01:58 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote:
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com>
wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence
that you and your production staff don't know enough about what you are
doing.
Don't be a jerk. We sell lots of the digital delay generator with the optional high-voltage outputs. It works great.
What are you designing lately?
Performance is what really matters, but getting stuff to look right is
also important.
Nobody has complained about the cosmetics of the pot core gap
alignment so far. We test every unit so the random alignment must not
matter.
On 1/23/26 15:13, john larkin wrote:
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>
The speed of electromagnet propagation is lower in Kapton that it is >>>>> dielectrics like teflon and polyethylene, which have lower dielectric >>>>> constants, but your Kapton flex probably wasn't designed to be a planar >>>>> transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll
go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
We are tight on PCB area, and we need to move on with the project. WeA regular pot core with connectorized micro-coax wound on a bobbin is >>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its
precise distribution. If you could find a wider, flatter ferrite core >>>>> you should be able to store more energy in the same vertical headroom. >>>>
can experiment with different ferrite materials once the boards are
built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so >>> that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that
Nickel-Zinc ferrites would work better you'd be confined to a smaller
range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
I was wondering: Do you actually use this transformer as a balun?
I mean, does the signal go in at one connector and out the other?
Or is it more like a transformer, where you use the core of the
coax as one winding and the shield as the other?
Jeroen Belleman
On Fri, 23 Jan 2026 15:57:29 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 3:31 am, john larkin wrote:
On Thu, 22 Jan 2026 17:57:24 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 11:34 am, john larkin wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>>
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>> energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the >>>>> same thing.
When people say "balun" they don't always mean balanced-to-unbalanced. >>>>>
You
*don't* want capacitive coupling between the ends. That would mess >>>>>> up the principal virtue of a balun.
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
Semi-rigid coax does. Regular coax - with a braid outer conductor - has >>>> around 95% shieding.
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Whoever mounted those pot core pair without lining up the gaps threw
away some of the energy storage you claim to be interested in.
True. The product works fine in production, but the misalignment might
matter a bit in my new GaN pulser. We'll experiment and see how much.
Of course it works adequately in production. The misalignment is only
going to create a small negative effect, but it is a very obvious
failure in quality control.
That's crazy. The gap alignment doesn't affect the output pulses, so
why should we control it?
You can worry about stuff like that on things that you design.
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>> are another version of the same idea, and the cores that are designed to >>>>>> be used with printed circuit windings do seem to be flatter and wider. >>>>>
The speed of electromagnet propagation is lower in Kapton that it is
dielectrics like teflon and polyethylene, which have lower dielectric
constants, but your Kapton flex probably wasn't designed to be a planar >>>> transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll
go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its
precise distribution. If you could find a wider, flatter ferrite core
you should be able to store more energy in the same vertical headroom.
We are tight on PCB area, and we need to move on with the project. We
can experiment with different ferrite materials once the boards are
built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so
that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that
Nickel-Zinc ferrites would work better you'd be confined to a smaller
range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
On 24/01/2026 1:24 am, john larkin wrote:
On Fri, 23 Jan 2026 15:57:29 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 3:31 am, john larkin wrote:
On Thu, 22 Jan 2026 17:57:24 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 22/01/2026 11:34 am, john larkin wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton >>>>>>>> flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>>> energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>>>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the >>>>>> same thing.
When people say "balun" they don't always mean balanced-to-unbalanced. >>>>>>
You
*don't* want capacitive coupling between the ends. That would mess >>>>>>> up the principal virtue of a balun.
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
Semi-rigid coax does. Regular coax - with a braid outer conductor - has >>>>> around 95% shieding.
We plan to buy a length of micro-coax with an SMB connector on each >>>>>> end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Whoever mounted those pot core pair without lining up the gaps threw >>>>> away some of the energy storage you claim to be interested in.
True. The product works fine in production, but the misalignment might >>>> matter a bit in my new GaN pulser. We'll experiment and see how much.
Of course it works adequately in production. The misalignment is only
going to create a small negative effect, but it is a very obvious
failure in quality control.
That's crazy. The gap alignment doesn't affect the output pulses, so
why should we control it?
So that your customers can see that you know what you are doing.
You can worry about stuff like that on things that you design.
I do. Sometimes it makes a bigger difference. Sometimes that can be >downright irritating. When I got to rework the weighting system on the >Cambridge Instruments GaAs crystal puller, I did all sorts of neat stuff
- including inventing a current mirror variant of the Baxandall class-D >oscillator - but the only thing that anybody noticed was that I replaced
a uA741 with a part that had a 1/f noise specification, and that meant
that the kilowatt or so of RF heating ran continuously at about 30% of
its maximum rating, rather than banging off for about minute and banging >back on at full throttle for about 30 seconds.
On 24/01/2026 1:13 am, john larkin wrote:
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA.
This will be a transmission-line transformer, and I want all the >>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in >>>>>>>> the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>
The speed of electromagnet propagation is lower in Kapton that it is >>>>> dielectrics like teflon and polyethylene, which have lower dielectric >>>>> constants, but your Kapton flex probably wasn't designed to be a planar >>>>> transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll
go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
We are tight on PCB area, and we need to move on with the project. WeA regular pot core with connectorized micro-coax wound on a bobbin is >>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less
energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its
precise distribution. If you could find a wider, flatter ferrite core >>>>> you should be able to store more energy in the same vertical headroom. >>>>
can experiment with different ferrite materials once the boards are
built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
It's even easier and quicker to look at the data sheets and think about
what they tell you.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so >>> that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that
Nickel-Zinc ferrites would work better you'd be confined to a smaller
range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
So you aren't designing for performance, but rather for ease of production.
On Sat, 24 Jan 2026 03:39:24 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 24/01/2026 1:13 am, john larkin wrote:
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>>
The speed of electromagnet propagation is lower in Kapton that it is >>>>>> dielectrics like teflon and polyethylene, which have lower dielectric >>>>>> constants, but your Kapton flex probably wasn't designed to be a planar >>>>>> transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll >>>>> go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
We are tight on PCB area, and we need to move on with the project. We >>>>> can experiment with different ferrite materials once the boards areA regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>> energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its >>>>>> precise distribution. If you could find a wider, flatter ferrite core >>>>>> you should be able to store more energy in the same vertical headroom. >>>>>
built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
It's even easier and quicker to look at the data sheets and think about
what they tell you.
Sure, but a test makes sense. Everybody verifies theories with tests.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so >>>> that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that
Nickel-Zinc ferrites would work better you'd be confined to a smaller
range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
So you aren't designing for performance, but rather for ease of production.
To make a product possible. We have a standard enclosure (a nice
custom extrusion) and a platform board to hang things on. It makes
sense to us to stuff in the biggest transformer that we can. More volt-seconds could make for more customers.
Producibility does matter since we pay the bills by making and selling electronics.
On Sat, 24 Jan 2026 03:35:16 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 24/01/2026 1:24 am, john larkin wrote:
On Fri, 23 Jan 2026 15:57:29 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 3:31 am, john larkin wrote:
On Thu, 22 Jan 2026 17:57:24 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:Of course it works adequately in production. The misalignment is only
On 22/01/2026 11:34 am, john larkin wrote:
On Wed, 21 Jan 2026 23:47:51 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/21/26 19:18, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>>>> nice, and easy to make in production. No soldering required. >>>>>>>>>
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>>>> energy than a full pot core.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Aren't you worried about the capacitive coupling between the windings? >>>>>>>> A piece of coax wound on a ferrite core is basically a balun.
I like to think of it as a transmission line transformer, but it's the >>>>>>> same thing.
When people say "balun" they don't always mean balanced-to-unbalanced. >>>>>>>
You
*don't* want capacitive coupling between the ends. That would mess >>>>>>>> up the principal virtue of a balun.
Coax has continuous capacitance from shield (primary) to center
(secondary). And shield-shield on the neaby windings.
Semi-rigid coax does. Regular coax - with a braid outer conductor - has >>>>>> around 95% shieding.
We plan to buy a length of micro-coax with an SMB connector on each >>>>>>> end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Whoever mounted those pot core pair without lining up the gaps threw >>>>>> away some of the energy storage you claim to be interested in.
True. The product works fine in production, but the misalignment might >>>>> matter a bit in my new GaN pulser. We'll experiment and see how much. >>>>
going to create a small negative effect, but it is a very obvious
failure in quality control.
That's crazy. The gap alignment doesn't affect the output pulses, so
why should we control it?
So that your customers can see that you know what you are doing.
If they open up our boxes and whine about the pot core alignment,
we'll just stop selling to the jerks.
That hasn't happened yet.
You can worry about stuff like that on things that you design.
I do. Sometimes it makes a bigger difference. Sometimes that can be
downright irritating. When I got to rework the weighting system on the
Cambridge Instruments GaAs crystal puller, I did all sorts of neat stuff
- including inventing a current mirror variant of the Baxandall class-D
oscillator - but the only thing that anybody noticed was that I replaced
a uA741 with a part that had a 1/f noise specification, and that meant
that the kilowatt or so of RF heating ran continuously at about 30% of
its maximum rating, rather than banging off for about minute and banging
back on at full throttle for about 30 seconds.
Those old 741s had popcorn noise.
On Fri, 23 Jan 2026 16:07:13 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/23/26 15:13, john larkin wrote:
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:My intern tried several experiments of making the windings from kapton >>>>>>> flex, but they weren't as fast as using coax.
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top >>>>>>>>> cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores >>>>>>>> are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider. >>>>>>>
The speed of electromagnet propagation is lower in Kapton that it is >>>>>> dielectrics like teflon and polyethylene, which have lower dielectric >>>>>> constants, but your Kapton flex probably wasn't designed to be a planar >>>>>> transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to
move on with life, and my intern has gone back to Cal Poly, so we'll >>>>> go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
We are tight on PCB area, and we need to move on with the project. We >>>>> can experiment with different ferrite materials once the boards areA regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>> energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its >>>>>> precise distribution. If you could find a wider, flatter ferrite core >>>>>> you should be able to store more energy in the same vertical headroom. >>>>>
built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so >>>> that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that
Nickel-Zinc ferrites would work better you'd be confined to a smaller
range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
I was wondering: Do you actually use this transformer as a balun?
I mean, does the signal go in at one connector and out the other?
Or is it more like a transformer, where you use the core of the
coax as one winding and the shield as the other?
Jeroen Belleman
We are using them as transformers. We drive the shield as the primary
and use the inner conductors as the secondary.
The usual config has a high-voltage power supply on one end of the
primary and a mosfet (now a GaN fet) slamming the other end to ground,
with programmable pulse delay and width.
The sec gives us an isolated pulse out of either polarity.
Since the windings are a transmission line, I guess the length of the
line limits how short a pulse we can make.
If we worked in balun mode, we couldn't make long pulses.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On 1/23/26 17:22, john larkin wrote:
On Fri, 23 Jan 2026 16:07:13 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/23/26 15:13, john larkin wrote:
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>> wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton >>>>>>>> flex, but they weren't as fast as using coax.
The speed of electromagnet propagation is lower in Kapton that it is >>>>>>> dielectrics like teflon and polyethylene, which have lower dielectric >>>>>>> constants, but your Kapton flex probably wasn't designed to be a planar >>>>>>> transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to >>>>>> move on with life, and my intern has gone back to Cal Poly, so we'll >>>>>> go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
We are tight on PCB area, and we need to move on with the project. We >>>>>> can experiment with different ferrite materials once the boards are >>>>>> built. There's lots available in this pot core size.A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>>> nice, and easy to make in production. No soldering required.
The Siemens/TKD ferrite core catalog might be worth reading. Here's a >>>>>>>>> small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>>> energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its >>>>>>> precise distribution. If you could find a wider, flatter ferrite core >>>>>>> you should be able to store more energy in the same vertical headroom. >>>>>>
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so >>>>> that you can mostly get away with Manganese-Zinc ferrites which are
normally only good for good couple of hundred kHz. If you found that >>>>> Nickel-Zinc ferrites would work better you'd be confined to a smaller >>>>> range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you
commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
I was wondering: Do you actually use this transformer as a balun?
I mean, does the signal go in at one connector and out the other?
Or is it more like a transformer, where you use the core of the
coax as one winding and the shield as the other?
Jeroen Belleman
We are using them as transformers. We drive the shield as the primary
and use the inner conductors as the secondary.
The usual config has a high-voltage power supply on one end of the
primary and a mosfet (now a GaN fet) slamming the other end to ground,
with programmable pulse delay and width.
The sec gives us an isolated pulse out of either polarity.
Since the windings are a transmission line, I guess the length of the
line limits how short a pulse we can make.
If we worked in balun mode, we couldn't make long pulses.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Something like the LTspice file below, I gather?
(I omit the common mode admittance of the transmission
line and the effect of interwinding capacitance.)
Jeroen Belleman
Version 4
SHEET 1 904 680
WIRE 240 96 64 96
WIRE 384 96 272 96
WIRE 512 96 384 96
WIRE 624 96 592 96
WIRE 240 144 240 96
WIRE 272 144 272 96
WIRE 64 176 64 96
WIRE 64 288 64 256
WIRE 272 320 272 240
WIRE 368 320 272 320
WIRE 512 320 368 320
WIRE 624 320 592 320
WIRE 240 336 240 240
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 624 96 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 624 320 0
FLAG 384 96 outp
FLAG 240 336 D
FLAG 368 320 outm
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 496 112 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL res 608 304 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 48 Left 2 !.tran 50n
On 24/01/2026 1:19 am, john larkin wrote:
On Fri, 23 Jan 2026 16:01:58 +1100, Bill Sloman <bill.sloman@ieee.org> wrote:
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote: >>>
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com> >>>> wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each >>>>> end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4 >>>>>j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence >> that you and your production staff don't know enough about what you are
doing.
Don't be a jerk. We sell lots of the digital delay generator with the optional high-voltage outputs. It works great.
Customers don't tend to open them up and look at the construction.
What are you designing lately?
Nothing much.
Performance is what really matters, but getting stuff to look right is
also important.
Nobody has complained about the cosmetics of the pot core gap
alignment so far. We test every unit so the random alignment must not matter.
It's not just the cosmetics. The random alignment doesn't matter much,
but it does make a difference, and you should have got it right.
Bill Sloman <bill.sloman@ieee.org> wrote:
On 24/01/2026 1:19 am, john larkin wrote:
On Fri, 23 Jan 2026 16:01:58 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com> >>>>>> wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each >>>>>>> end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4 >>>>>>> j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence >>>> that you and your production staff don't know enough about what you are >>>> doing.
Don't be a jerk. We sell lots of the digital delay generator with the
optional high-voltage outputs. It works great.
Customers don't tend to open them up and look at the construction.
What are you designing lately?
Nothing much.
Performance is what really matters, but getting stuff to look right is >>>> also important.
Nobody has complained about the cosmetics of the pot core gap
alignment so far. We test every unit so the random alignment must not
matter.
It's not just the cosmetics. The random alignment doesn't matter much,
but it does make a difference, and you should have got it right.
It depends on which way is 'right'. If the bobbin is in two sections
and has two separate windings which must be kept apart, staggering the 'windows' will ensure that the leads from the two windings are brought
out in different places and they cannot stray anywhere near each other.
On 25/01/2026 6:25 am, Liz Tuddenham wrote:
Bill Sloman <bill.sloman@ieee.org> wrote:
On 24/01/2026 1:19 am, john larkin wrote:
On Fri, 23 Jan 2026 16:01:58 +1100, Bill Sloman <bill.sloman@ieee.org> >>> wrote:
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com> >>>>>> wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each >>>>>>> end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4 >>>>>>> j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration >>>>>> absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence >>>> that you and your production staff don't know enough about what you are >>>> doing.
Don't be a jerk. We sell lots of the digital delay generator with the
optional high-voltage outputs. It works great.
Customers don't tend to open them up and look at the construction.
What are you designing lately?
Nothing much.
Performance is what really matters, but getting stuff to look right is >>>> also important.
Nobody has complained about the cosmetics of the pot core gap
alignment so far. We test every unit so the random alignment must not
matter.
It's not just the cosmetics. The random alignment doesn't matter much,
but it does make a difference, and you should have got it right.
It depends on which way is 'right'. If the bobbin is in two sections
and has two separate windings which must be kept apart, staggering the 'windows' will ensure that the leads from the two windings are brought
out in different places and they cannot stray anywhere near each other.
That's the sort of scheme you get with people who don't know what they
are doing.
If you don't want two pairs of leads to interact, twist each pair of
leads and take them out through different slots.
Twisting each pair of leads separately is a much more potent protection against interaction than just keeping them physically separate.
On Sat, 24 Jan 2026 12:17:44 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/23/26 17:22, john larkin wrote:
On Fri, 23 Jan 2026 16:07:13 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/23/26 15:13, john larkin wrote:
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
The speed of electromagnet propagation is lower in Kapton that it is >>>>>>>> dielectrics like teflon and polyethylene, which have lower dielectric >>>>>>>> constants, but your Kapton flex probably wasn't designed to be a planar
transmission line.
We made several and we sure intended them to be txline windings.
The road to hell is paved with good intentions.
We
don't understand why the planar windings were slow, but we need to >>>>>>> move on with life, and my intern has gone back to Cal Poly, so we'll >>>>>>> go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And
it's fun.
Well, maybe you know everything already and don't approve of fun.
We are tight on PCB area, and we need to move on with the project. We >>>>>>> can experiment with different ferrite materials once the boards are >>>>>>> built. There's lots available in this pot core size.A regular pot core with connectorized micro-coax wound on a bobbin is >>>>>>>>> nice, and easy to make in production. No soldering required. >>>>>>>>>
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>>>> energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its >>>>>>>> precise distribution. If you could find a wider, flatter ferrite core >>>>>>>> you should be able to store more energy in the same vertical headroom. >>>>>>>
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so >>>>>> that you can mostly get away with Manganese-Zinc ferrites which are >>>>>> normally only good for good couple of hundred kHz. If you found that >>>>>> Nickel-Zinc ferrites would work better you'd be confined to a smaller >>>>>> range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you >>>>>> commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
I was wondering: Do you actually use this transformer as a balun?
I mean, does the signal go in at one connector and out the other?
Or is it more like a transformer, where you use the core of the
coax as one winding and the shield as the other?
Jeroen Belleman
We are using them as transformers. We drive the shield as the primary
and use the inner conductors as the secondary.
The usual config has a high-voltage power supply on one end of the
primary and a mosfet (now a GaN fet) slamming the other end to ground,
with programmable pulse delay and width.
The sec gives us an isolated pulse out of either polarity.
Since the windings are a transmission line, I guess the length of the
line limits how short a pulse we can make.
If we worked in balun mode, we couldn't make long pulses.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Something like the LTspice file below, I gather?
(I omit the common mode admittance of the transmission
line and the effect of interwinding capacitance.)
Jeroen Belleman
Version 4
[Deleted...]
That's it. The timing of the OUTP and OUTM nodes is interesting,
skewed by the line delay. That makes the differential output goofy.
That effect ceates a mess of tradeoffs.
Adding inductance makes it worse. Nonlinear L, even worse.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Bill Sloman <bill.sloman@ieee.org> wrote:
On 24/01/2026 1:19 am, john larkin wrote:
On Fri, 23 Jan 2026 16:01:58 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote: >> >>>
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com> >> >>>> wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each
end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4 >> >>>>>j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence >> >> that you and your production staff don't know enough about what you are >> >> doing.
Don't be a jerk. We sell lots of the digital delay generator with the
optional high-voltage outputs. It works great.
Customers don't tend to open them up and look at the construction.
What are you designing lately?
Nothing much.
Performance is what really matters, but getting stuff to look right is
also important.
Nobody has complained about the cosmetics of the pot core gap
alignment so far. We test every unit so the random alignment must not
matter.
It's not just the cosmetics. The random alignment doesn't matter much,
but it does make a difference, and you should have got it right.
It depends on which way is 'right'. If the bobbin is in two sections
and has two separate windings which must be kept apart, staggering the >'windows' will ensure that the leads from the two windings are brought
out in different places and they cannot stray anywhere near each other..
On 1/24/26 16:54, john larkin wrote:
On Sat, 24 Jan 2026 12:17:44 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/23/26 17:22, john larkin wrote:
On Fri, 23 Jan 2026 16:07:13 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/23/26 15:13, john larkin wrote:
On Fri, 23 Jan 2026 16:16:00 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 23/01/2026 6:09 am, john larkin wrote:
On Thu, 22 Jan 2026 17:51:12 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>> wrote:The road to hell is paved with good intentions.
On 22/01/2026 5:18 am, john larkin wrote:
On Thu, 22 Jan 2026 04:49:33 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 22/01/2026 3:45 am, john larkin wrote:
https://www.dropbox.com/scl/fi/d7xug1xxazoishocjcwbm/R250_Pot_Core.jpg?rlkey=sakv9lo5ov4a8lx4cjoxzn8f6&raw=1
My mechanical design guy is great, and pot cores are a PITA. >>>>>>>>>>>>
This will be a transmission-line transformer, and I want all the >>>>>>>>>>>> volt-seconds possible, so the pot core has to be big and barely fit in
the box. I've argued that zero vertical clearance is OK - let the top
cover and the PCB flex a bit - but mechanical people don't seem to >>>>>>>>>>>> like that idea.
Pot cores aren't the only shaped bits of ferrite you can buy. RM cores
are another version of the same idea, and the cores that are designed to
be used with printed circuit windings do seem to be flatter and wider.
My intern tried several experiments of making the windings from kapton
flex, but they weren't as fast as using coax.
The speed of electromagnet propagation is lower in Kapton that it is >>>>>>>>> dielectrics like teflon and polyethylene, which have lower dielectric >>>>>>>>> constants, but your Kapton flex probably wasn't designed to be a planar
transmission line.
We made several and we sure intended them to be txline windings. >>>>>>>
We
don't understand why the planar windings were slow, but we need to >>>>>>>> move on with life, and my intern has gone back to Cal Poly, so we'll >>>>>>>> go with connectorized coax. That is known to work.
Don't mess with stuff you don't understand.
We should mess with stuff we don't understand. We learn things. And >>>>>> it's fun.
Well, maybe you know everything already and don't approve of fun.
A regular pot core with connectorized micro-coax wound on a bobbin is
nice, and easy to make in production. No soldering required. >>>>>>>>>>
The Siemens/TKD ferrite core catalog might be worth reading. Here's a
small chunk.
https://www.tdk-electronics.tdk.com/en/529402/products/product-catalog/ferrites-and-accessories/pq-cores-and-accessories
We have samples like that. Seems to me that they would store less >>>>>>>>>> energy than a full pot core.
What matters to you is the total volume of ferrite, rather than its >>>>>>>>> precise distribution. If you could find a wider, flatter ferrite core >>>>>>>>> you should be able to store more energy in the same vertical headroom.
We are tight on PCB area, and we need to move on with the project. We >>>>>>>> can experiment with different ferrite materials once the boards are >>>>>>>> built. There's lots available in this pot core size.
But perhaps not the particular ferrite which would work best.
It's not hard to buy a bunch and try them.
The thing about transmission line transformers is that the high
frequency currents are pretty much confined to the transmission line, so
that you can mostly get away with Manganese-Zinc ferrites which are >>>>>>> normally only good for good couple of hundred kHz. If you found that >>>>>>> Nickel-Zinc ferrites would work better you'd be confined to a smaller >>>>>>> range of cores.
Design is often a question of balancing lots of contradictory
constraints. It pays to know something about all of them before you >>>>>>> commit yourself to a particular volumetric limit.
This pot core uses about all the volume that we have, and it's a
standard size that lots of people make.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
I was wondering: Do you actually use this transformer as a balun?
I mean, does the signal go in at one connector and out the other?
Or is it more like a transformer, where you use the core of the
coax as one winding and the shield as the other?
Jeroen Belleman
We are using them as transformers. We drive the shield as the primary
and use the inner conductors as the secondary.
The usual config has a high-voltage power supply on one end of the
primary and a mosfet (now a GaN fet) slamming the other end to ground, >>>> with programmable pulse delay and width.
The sec gives us an isolated pulse out of either polarity.
Since the windings are a transmission line, I guess the length of the
line limits how short a pulse we can make.
If we worked in balun mode, we couldn't make long pulses.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Something like the LTspice file below, I gather?
(I omit the common mode admittance of the transmission
line and the effect of interwinding capacitance.)
Jeroen Belleman
Version 4
[Deleted...]
That's it. The timing of the OUTP and OUTM nodes is interesting,
skewed by the line delay. That makes the differential output goofy.
That effect ceates a mess of tradeoffs.
Adding inductance makes it worse. Nonlinear L, even worse.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
I know it doesn't fit within your present constraints, but maybe
for a future upgrade, how about something like the arrangement
below? Coax T1 and T2 sit in the same magnetic core. You could
use a single 25 Ohm coax. The actual lengths do not matter, as
long as T1=T2 and T3=T4. T3 needs its own core, but T4 does not.
It produces pulses with the full supply amplitude and aligns
the positive and negative outputs. It's also a heavier load
on the switch, of course.
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
Bill Sloman <bill.sloman@ieee.org> wrote:
On 25/01/2026 6:25 am, Liz Tuddenham wrote:
Bill Sloman <bill.sloman@ieee.org> wrote:
On 24/01/2026 1:19 am, john larkin wrote:
On Fri, 23 Jan 2026 16:01:58 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>>>
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com> >>>>>>>> wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each >>>>>>>>> end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4 >>>>>>>>> j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration >>>>>>>> absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2% >>>>>>> change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence >>>>>> that you and your production staff don't know enough about what you are >>>>>> doing.
Don't be a jerk. We sell lots of the digital delay generator with the >>>>> optional high-voltage outputs. It works great.
Customers don't tend to open them up and look at the construction.
What are you designing lately?
Nothing much.
Performance is what really matters, but getting stuff to look right is >>>>>> also important.
Nobody has complained about the cosmetics of the pot core gap
alignment so far. We test every unit so the random alignment must not >>>>> matter.
It's not just the cosmetics. The random alignment doesn't matter much, >>>> but it does make a difference, and you should have got it right.
It depends on which way is 'right'. If the bobbin is in two sections
and has two separate windings which must be kept apart, staggering the
'windows' will ensure that the leads from the two windings are brought
out in different places and they cannot stray anywhere near each other.
That's the sort of scheme you get with people who don't know what they
are doing.
If you don't want two pairs of leads to interact, twist each pair of
leads and take them out through different slots.
Twisting each pair of leads separately is a much more potent protection
against interaction than just keeping them physically separate.
That's the sort of reply you get from someone who hasn't understood the previous post.
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Bill Sloman <bill.sloman@ieee.org> wrote:
On 24/01/2026 1:19 am, john larkin wrote:
On Fri, 23 Jan 2026 16:01:58 +1100, Bill Sloman <bill.sloman@ieee.org> >>> > wrote:
On 23/01/2026 5:57 am, john larkin wrote:
On Thu, 22 Jan 2026 10:58:01 -0500, legg <legg@nospam.magma.ca> wrote: >>> >>>
On Wed, 21 Jan 2026 16:34:34 -0800, john larkin <jl@glen--canyon.com> >>> >>>> wrote:
<snip>
We plan to buy a length of micro-coax with an SMB connector on each >>> >>>>> end. We'll wind that on the bobbin and plug it into pcb SMB
connectors.
Like this, but higher voltage.
https://www.dropbox.com/scl/fi/9hbvwwo2bmx4z33w9uetv/TX_1.jpg?rlkey=4 >>> >>>>>j8llr8z6z360ec5b8adx53gz&raw=1
Those tiny H.FL connectors can't take much voltage.
Mount the transformer on the box wallwith on a layer of vibration
absorber.
Connect your flying leads as required.
Energy storage ~ minimum xsectional area - not mass. . . .
so align your slots.
RL
We like to put parts on PC boards. But why vibration isolation?
We will use a bigger pot core on the new product. I measured a 2%
change in inductance as the core halves were rotated, so slot
alignment is no big deal.
It doesn't degrade the performance much, but it is very visible evidence >>> >> that you and your production staff don't know enough about what you are >>> >> doing.
Don't be a jerk. We sell lots of the digital delay generator with the
optional high-voltage outputs. It works great.
Customers don't tend to open them up and look at the construction.
What are you designing lately?
Nothing much.
Performance is what really matters, but getting stuff to look right is >>> >> also important.
Nobody has complained about the cosmetics of the pot core gap
alignment so far. We test every unit so the random alignment must not
matter.
It's not just the cosmetics. The random alignment doesn't matter much,
but it does make a difference, and you should have got it right.
It depends on which way is 'right'. If the bobbin is in two sections
and has two separate windings which must be kept apart, staggering the >>'windows' will ensure that the leads from the two windings are brought
out in different places and they cannot stray anywhere near each other..
In applications where power levels are important, pot core orientation
will affect 'N' in the flux density concentration, and produce early >saturation at the location where minimum x-sectional area occurs.
RL
On Sun, 25 Jan 2026 13:04:14 +0100, Jeroen Belleman[...]
<jeroen@nospam.please> wrote:
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
It throws a "Multiple Instances of Flag" error
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On 1/25/26 16:33, john larkin wrote:
On Sun, 25 Jan 2026 13:04:14 +0100, Jeroen Belleman[...]
<jeroen@nospam.please> wrote:
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
It throws a "Multiple Instances of Flag" error
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
That's a nuisance. I downloaded it again from your answer and it works
fine here. I tried googling for that error message, but it typically
seems to occur when subcircuits are included, and I don't do that.
Eyeballing the .asc text, looking for anything duplicated, didn't help >either. I'm a bit at a loss here.
Could you try removing all the lines starting with 'FLAG'? The file
will still open in the schematic editor, but now all the GND connections
are gone, as are the node names. Insert GNDs again by hand. They are
all at the ends of bits of wire.
Jeroen Belleman
On 1/25/26 16:33, john larkin wrote:
On Sun, 25 Jan 2026 13:04:14 +0100, Jeroen Belleman[...]
<jeroen@nospam.please> wrote:
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
It throws a "Multiple Instances of Flag" error
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
That's a nuisance. I downloaded it again from your answer and it works
fine here. I tried googling for that error message, but it typically
seems to occur when subcircuits are included, and I don't do that.
Eyeballing the .asc text, looking for anything duplicated, didn't help >either. I'm a bit at a loss here.
Could you try removing all the lines starting with 'FLAG'? The file
will still open in the schematic editor, but now all the GND connections
are gone, as are the node names. Insert GNDs again by hand. They are
all at the ends of bits of wire.
Jeroen Belleman
On Sun, 25 Jan 2026 17:32:40 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/25/26 16:33, john larkin wrote:
On Sun, 25 Jan 2026 13:04:14 +0100, Jeroen Belleman[...]
<jeroen@nospam.please> wrote:
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
It throws a "Multiple Instances of Flag" error
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
That's a nuisance. I downloaded it again from your answer and it works
fine here. I tried googling for that error message, but it typically
seems to occur when subcircuits are included, and I don't do that. >>Eyeballing the .asc text, looking for anything duplicated, didn't help >>either. I'm a bit at a loss here.
Could you try removing all the lines starting with 'FLAG'? The file
will still open in the schematic editor, but now all the GND connections >>are gone, as are the node names. Insert GNDs again by hand. They are
all at the ends of bits of wire.
Jeroen Belleman
Weird. If I edit it down to one FLAG, it complains about multiple
SYMATTRs. I think multiple symattrys are legal.
Your other circuit worked fine.
What is a FLAG anyhow? The help doesn't say.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On Sun, 25 Jan 2026 11:12:56 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 17:32:40 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 1/25/26 16:33, john larkin wrote:
On Sun, 25 Jan 2026 13:04:14 +0100, Jeroen Belleman[...]
<jeroen@nospam.please> wrote:
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
It throws a "Multiple Instances of Flag" error
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
That's a nuisance. I downloaded it again from your answer and it works >>>fine here. I tried googling for that error message, but it typically >>>seems to occur when subcircuits are included, and I don't do that. >>>Eyeballing the .asc text, looking for anything duplicated, didn't help >>>either. I'm a bit at a loss here.
Could you try removing all the lines starting with 'FLAG'? The file >>>will still open in the schematic editor, but now all the GND connections >>>are gone, as are the node names. Insert GNDs again by hand. They are
all at the ends of bits of wire.
Jeroen Belleman
Weird. If I edit it down to one FLAG, it complains about multiple
SYMATTRs. I think multiple symattrys are legal.
Your other circuit worked fine.
What is a FLAG anyhow? The help doesn't say.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It denotes a graphical (such as ground symbol) or text (such as net
name) item.
Go to tools/color preferences and you can give change the flag item
colours to see where they are on the schematic.
On Sun, 25 Jan 2026 19:44:41 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Sun, 25 Jan 2026 11:12:56 -0800, john larkin <jl@glen--canyon.com> >>wrote:
On Sun, 25 Jan 2026 17:32:40 +0100, Jeroen Belleman >>><jeroen@nospam.please> wrote:
On 1/25/26 16:33, john larkin wrote:
On Sun, 25 Jan 2026 13:04:14 +0100, Jeroen Belleman[...]
<jeroen@nospam.please> wrote:
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
It throws a "Multiple Instances of Flag" error
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
That's a nuisance. I downloaded it again from your answer and it works >>>>fine here. I tried googling for that error message, but it typically >>>>seems to occur when subcircuits are included, and I don't do that. >>>>Eyeballing the .asc text, looking for anything duplicated, didn't help >>>>either. I'm a bit at a loss here.
Could you try removing all the lines starting with 'FLAG'? The file >>>>will still open in the schematic editor, but now all the GND connections >>>>are gone, as are the node names. Insert GNDs again by hand. They are >>>>all at the ends of bits of wire.
Jeroen Belleman
Weird. If I edit it down to one FLAG, it complains about multiple >>>SYMATTRs. I think multiple symattrys are legal.
Your other circuit worked fine.
What is a FLAG anyhow? The help doesn't say.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It denotes a graphical (such as ground symbol) or text (such as net
name) item.
Go to tools/color preferences and you can give change the flag item
colours to see where they are on the schematic.
I fixed it. I copied the text from Jeroen's post, into a text editor,
and saved it but didn't include the .asc extension. LT Spice then
threw the weird errors.
LT is great but kinda weird and definitely under-HELPed.
Looks like FLAG x y 0
is a ground.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On Sun, 25 Jan 2026 13:07:32 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 19:44:41 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Sun, 25 Jan 2026 11:12:56 -0800, john larkin <jl@glen--canyon.com> >>>wrote:
On Sun, 25 Jan 2026 17:32:40 +0100, Jeroen Belleman >>>><jeroen@nospam.please> wrote:
On 1/25/26 16:33, john larkin wrote:
On Sun, 25 Jan 2026 13:04:14 +0100, Jeroen Belleman[...]
<jeroen@nospam.please> wrote:
Jeroen Belleman
===============================
Version 4
SHEET 1 1476 680
WIRE 240 0 64 0
WIRE 864 0 240 0
WIRE 416 128 272 128
WIRE 576 128 512 128
WIRE 624 128 576 128
WIRE 736 128 704 128
WIRE 1040 128 896 128
WIRE 1168 128 1168 96
WIRE 1168 128 1136 128
WIRE 240 144 240 0
WIRE 272 144 272 128
WIRE 864 144 864 0
WIRE 896 144 896 128
WIRE 416 160 352 160
WIRE 576 160 512 160
WIRE 1040 160 976 160
WIRE 1232 160 1136 160
WIRE 1296 160 1232 160
WIRE 1456 160 1376 160
WIRE 64 176 64 0
WIRE 352 176 352 160
WIRE 576 176 576 160
WIRE 976 176 976 160
WIRE 272 256 272 240
WIRE 320 256 272 256
WIRE 896 256 896 240
WIRE 944 256 896 256
WIRE 64 288 64 256
WIRE 240 304 240 240
WIRE 864 304 864 240
WIRE 864 304 240 304
WIRE 240 336 240 304
WIRE 240 368 240 336
WIRE 192 384 96 384
WIRE 192 432 96 432
WIRE 96 448 96 432
WIRE 240 480 240 448
WIRE 96 544 96 528
FLAG 64 288 0
FLAG 240 480 0
FLAG 736 128 0
FLAG 96 384 0
FLAG 96 544 0
FLAG 576 128 outp
FLAG 240 336 D
FLAG 320 256 0
FLAG 944 256 0
FLAG 1456 160 0
FLAG 976 176 0
FLAG 1168 96 0
FLAG 1232 160 outm
FLAG 576 176 0
FLAG 352 176 0
SYMBOL voltage 64 160 R0
SYMATTR InstName V1
SYMATTR Value 100
SYMBOL tline 256 192 R90
SYMATTR InstName T1
SYMATTR Value Td=5n Z0=50
SYMBOL sw 240 352 R0
SYMATTR InstName S1
SYMATTR Value myswitch
SYMBOL res 608 144 R270
WINDOW 0 32 56 VTop 2
WINDOW 3 0 56 VBottom 2
SYMATTR InstName R1
SYMATTR Value 50
SYMBOL voltage 96 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 1 1n 1n 1n 15n)
SYMBOL tline 880 192 R90
SYMATTR InstName T2
SYMATTR Value Td=5n Z0=50
SYMBOL res 1392 144 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R2
SYMATTR Value 50
SYMBOL tline 1088 144 R0
SYMATTR InstName T3
SYMATTR Value Td=5n Z0=50
SYMBOL tline 464 144 R0
SYMATTR InstName T4
SYMATTR Value Td=5n Z0=50
TEXT 296 408 Left 2 !.model myswitch SW(Ron=10m roff=1G Vt=0.5)
TEXT 96 -16 Left 2 !.tran 50n
It throws a "Multiple Instances of Flag" error
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
That's a nuisance. I downloaded it again from your answer and it works >>>>>fine here. I tried googling for that error message, but it typically >>>>>seems to occur when subcircuits are included, and I don't do that. >>>>>Eyeballing the .asc text, looking for anything duplicated, didn't help >>>>>either. I'm a bit at a loss here.
Could you try removing all the lines starting with 'FLAG'? The file >>>>>will still open in the schematic editor, but now all the GND connections >>>>>are gone, as are the node names. Insert GNDs again by hand. They are >>>>>all at the ends of bits of wire.
Jeroen Belleman
Weird. If I edit it down to one FLAG, it complains about multiple >>>>SYMATTRs. I think multiple symattrys are legal.
Your other circuit worked fine.
What is a FLAG anyhow? The help doesn't say.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It denotes a graphical (such as ground symbol) or text (such as net >>>name) item.
Go to tools/color preferences and you can give change the flag item >>>colours to see where they are on the schematic.
I fixed it. I copied the text from Jeroen's post, into a text editor,
and saved it but didn't include the .asc extension. LT Spice then
threw the weird errors.
LT is great but kinda weird and definitely under-HELPed.
Wurth seems to be giving their book away for free. It's probably the
closest to a user guide.
https://mega.nz/file/htcjUT6b#dkY5IZffmfKrU6g-456-l5BVwJgWctAe28oxcCcthiw
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote:<snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation
will affect 'N' in the flux density concentration, and produce early >>saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote:<snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation
will affect 'N' in the flux density concentration, and produce early
saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
On 26/01/2026 2:44 pm, legg wrote:
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote:<snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>> will affect 'N' in the flux density concentration, and produce early
saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
There is a way of doing trolerance trims on some gapped pot cores.
The manufactures put cylindrical hole down through the centre of the
core, and sell an adjustor which plugs into the hole. There a ferrite
slug in the adjustor which you can screw up and down to fully or
completely bridge the the gap between two core halves.
I've used them, and they provide enough adjustment to let you trim out
the residual tolerance on the inductance of a gapped core which can get
up to perhaps +/-5%, and a bit more.
The one time when I designed one in to get a precise 15MHz source for TV >style video, one of my colleague engineers copied the design for a much >higher volume project, he left out the adjustor - we were also using a >varactor diode to accomodate the frequency difference between production
TV displays and he figured that that - one its own - could cope with
both sources of variation. Varactors are very non-linear, and I was
worried about getting out of the region where they were linear enough.
Jerry was a very good engineer - if not all that self-confident - and
I'd been warned off expressing any doubts about his designs, because
he'd take my doubts much too seriously.
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote:<snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>will affect 'N' in the flux density concentration, and produce early >>>saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
RL
On Mon, 26 Jan 2026 17:56:10 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/01/2026 2:44 pm, legg wrote:
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote: >>>><snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid >>>>> (Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>>> will affect 'N' in the flux density concentration, and produce early >>>>> saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
There is a way of doing trolerance trims on some gapped pot cores.
The manufactures put cylindrical hole down through the centre of the
core, and sell an adjustor which plugs into the hole. There a ferrite
slug in the adjustor which you can screw up and down to fully or
completely bridge the the gap between two core halves.
I've used them, and they provide enough adjustment to let you trim out
the residual tolerance on the inductance of a gapped core which can get
up to perhaps +/-5%, and a bit more.
The one time when I designed one in to get a precise 15MHz source for TV
style video, one of my colleague engineers copied the design for a much
higher volume project, he left out the adjustor - we were also using a
varactor diode to accomodate the frequency difference between production
TV displays and he figured that that - one its own - could cope with
both sources of variation. Varactors are very non-linear, and I was
worried about getting out of the region where they were linear enough.
Jerry was a very good engineer - if not all that self-confident - and
I'd been warned off expressing any doubts about his designs, because
he'd take my doubts much too seriously.
Pot cores were developed for tube-amplitude cctry. I expect that
adjustible varieties had added cost. How did it compare in cost to
the addition of a varactor?
For semiconductors, you'd get away with slug tuned 'can' - still
candidate for a varactor.
Lots of headaches with pot cores - mounting, termination etc. The
smaller parts actually increased in price . . . .
On Sun, 25 Jan 2026 22:44:02 -0500, legg <legg@nospam.magma.ca> wrote:
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote:<snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>> will affect 'N' in the flux density concentration, and produce early
saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
Impregnation?
On 27/01/2026 2:53 am, john larkin wrote:
On Sun, 25 Jan 2026 22:44:02 -0500, legg <legg@nospam.magma.ca> wrote:
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote: >>>><snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid >>>>> (Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>>> will affect 'N' in the flux density concentration, and produce early >>>>> saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
Impregnation?
Some people like to lock the windings and the leads in place with a
heavy layer of encapsulant. This works better if you put the part to >encapsulated under vacuum before you pour on the encapsulant.
I've never seen it done, but I've heard about it. It's apparently very >messy.
On Mon, 26 Jan 2026 17:56:10 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/01/2026 2:44 pm, legg wrote:
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote: >>>><snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid >>>>> (Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>>> will affect 'N' in the flux density concentration, and produce early >>>>> saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
There is a way of doing trolerance trims on some gapped pot cores.
The manufactures put cylindrical hole down through the centre of the
core, and sell an adjustor which plugs into the hole. There a ferrite >>slug in the adjustor which you can screw up and down to fully or >>completely bridge the the gap between two core halves.
I've used them, and they provide enough adjustment to let you trim out
the residual tolerance on the inductance of a gapped core which can get
up to perhaps +/-5%, and a bit more.
The one time when I designed one in to get a precise 15MHz source for TV >>style video, one of my colleague engineers copied the design for a much >>higher volume project, he left out the adjustor - we were also using a >>varactor diode to accomodate the frequency difference between production >>TV displays and he figured that that - one its own - could cope with
both sources of variation. Varactors are very non-linear, and I was >>worried about getting out of the region where they were linear enough.
Jerry was a very good engineer - if not all that self-confident - and
I'd been warned off expressing any doubts about his designs, because
he'd take my doubts much too seriously.
Pot cores were developed for tube-amplitude cctry. I expect that
adjustible varieties had added cost. How did it compare in cost to
the addition of a varactor?
For semiconductors, you'd get away with slug tuned 'can' - still
candidate for a varactor.
Lots of headaches with pot cores - mounting, termination etc. The
smaller parts actually increased in price . . . .
RL
On Tue, 27 Jan 2026 03:36:36 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/01/2026 2:53 am, john larkin wrote:
On Sun, 25 Jan 2026 22:44:02 -0500, legg <legg@nospam.magma.ca> wrote:
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote: >>>>><snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid >>>>>> (Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>>>> will affect 'N' in the flux density concentration, and produce early >>>>>> saturation at the location where minimum x-sectional area occurs.
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
Impregnation?
Some people like to lock the windings and the leads in place with a
heavy layer of encapsulant. This works better if you put the part to
encapsulated under vacuum before you pour on the encapsulant.
I've never seen it done, but I've heard about it. It's apparently very
messy.
Wet stuff is messy, really nasty in production. In the case of a
txline transformer made with a few turns of coax, there's no reason to
pot it.
We just spin a few turns on a bobbin and clamp it into the pot core.
If it got sloppy, a tie-wrap would secure things.
Some people like the idea of potting things. Weird.
On 2026-01-26 11:48, john larkin wrote:
On Tue, 27 Jan 2026 03:36:36 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/01/2026 2:53 am, john larkin wrote:
On Sun, 25 Jan 2026 22:44:02 -0500, legg <legg@nospam.magma.ca> wrote: >>>>
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com> >>>>> wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>><snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid >>>>>>> (Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>>>>> will affect 'N' in the flux density concentration, and produce early >>>>>>> saturation at the location where minimum x-sectional area occurs. >>>>>>>
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
Impregnation?
Some people like to lock the windings and the leads in place with a
heavy layer of encapsulant. This works better if you put the part to
encapsulated under vacuum before you pour on the encapsulant.
I've never seen it done, but I've heard about it. It's apparently very
messy.
Wet stuff is messy, really nasty in production. In the case of a
txline transformer made with a few turns of coax, there's no reason to
pot it.
We just spin a few turns on a bobbin and clamp it into the pot core.
If it got sloppy, a tie-wrap would secure things.
Some people like the idea of potting things. Weird.
Last year we did a TDR that had to survive being pounded into hardpan
with a slide hammer (>20k gees). Potting was the right answer there!
We put in small bits of foam sticky tape to keep the epoxy from trashing
the pulse shapes. If we did it again, we'd probably go to a six-layer
board and use stripline to avoid the problem (mostly).
Cheers
Phil Hobbs
On Mon, 26 Jan 2026 13:12:21 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-01-26 11:48, john larkin wrote:
On Tue, 27 Jan 2026 03:36:36 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/01/2026 2:53 am, john larkin wrote:
On Sun, 25 Jan 2026 22:44:02 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com> >>>>>> wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>>><snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid >>>>>>>> (Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>>>>>> will affect 'N' in the flux density concentration, and produce early >>>>>>>> saturation at the location where minimum x-sectional area occurs. >>>>>>>>
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
Impregnation?
Some people like to lock the windings and the leads in place with a
heavy layer of encapsulant. This works better if you put the part to
encapsulated under vacuum before you pour on the encapsulant.
I've never seen it done, but I've heard about it. It's apparently very >>>> messy.
Wet stuff is messy, really nasty in production. In the case of a
txline transformer made with a few turns of coax, there's no reason to
pot it.
We just spin a few turns on a bobbin and clamp it into the pot core.
If it got sloppy, a tie-wrap would secure things.
Some people like the idea of potting things. Weird.
Last year we did a TDR that had to survive being pounded into hardpan
with a slide hammer (>20k gees). Potting was the right answer there!
We put in small bits of foam sticky tape to keep the epoxy from trashing
the pulse shapes. If we did it again, we'd probably go to a six-layer
board and use stripline to avoid the problem (mostly).
Hard-cure epoxy can crush and destroy parts too. And, I've heard,
wreck opamp offsets.
JLC does cheap 6-layers.
On Mon, 26 Jan 2026 13:12:21 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2026-01-26 11:48, john larkin wrote:
On Tue, 27 Jan 2026 03:36:36 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/01/2026 2:53 am, john larkin wrote:
On Sun, 25 Jan 2026 22:44:02 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>
On Sun, 25 Jan 2026 08:08:48 -0800, john larkin <jl@glen--canyon.com> >>>>>> wrote:
On Sun, 25 Jan 2026 08:51:24 -0500, legg <legg@nospam.magma.ca> wrote: >>>>>>><snip>
On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid >>>>>>>> (Liz Tuddenham) wrote:
In applications where power levels are important, pot core orientation >>>>>>>> will affect 'N' in the flux density concentration, and produce early >>>>>>>> saturation at the location where minimum x-sectional area occurs. >>>>>>>>
RL
That should have a small effect on my pulser. Ill try it.
I got a 2% change in inductance when I rotated the core halves.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
2% FREE x-sectional area, and an indication that the previous
misalignment doesn't dominate minimum value.
Mind you, you can get a similar change just by forcing out
the fluff and detritus present at the contacting surfaces.
That might be what you're actually seeing, even if the core
is gapped.
In pot cores, minimum x-section usually occurs where the centre
core meets the top and bottom plates. In parts shapes designed
for power applications, this is usually corrected.
This core rotation can be used as a tolerance trim, where
needed, but anything like that before impregnation is probably
just biting fart bubbles.
Impregnation?
Some people like to lock the windings and the leads in place with a
heavy layer of encapsulant. This works better if you put the part to
encapsulated under vacuum before you pour on the encapsulant.
I've never seen it done, but I've heard about it. It's apparently very >>>> messy.
Wet stuff is messy, really nasty in production. In the case of a
txline transformer made with a few turns of coax, there's no reason to
pot it.
We just spin a few turns on a bobbin and clamp it into the pot core.
If it got sloppy, a tie-wrap would secure things.
Some people like the idea of potting things. Weird.
Last year we did a TDR that had to survive being pounded into hardpan
with a slide hammer (>20k gees). Potting was the right answer there!
We put in small bits of foam sticky tape to keep the epoxy from trashing
the pulse shapes. If we did it again, we'd probably go to a six-layer
board and use stripline to avoid the problem (mostly).
Cheers
Phil Hobbs
Hard-cure epoxy can crush and destroy parts too. And, I've heard,
wreck opamp offsets.
JLC does cheap 6-layers.
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