Re: mounting a pot core

From	john larkin <jl@glen--canyon.com>
Newsgroups	sci.electronics.design
Subject	Re: mounting a pot core
Date	2026-01-21 17:06 -0800
Organization	Highland Technology
Message-ID	<lpt2nkt0cuaj3pmfb13203qaes0j9fppvn@4ax.com> (permalink)
References	(1 earlier) <10kr3jl$29sd5$1@dont-email.me> <0o52nkd28caho2s8ier753k3j14kvg8obo@4ax.com> <10krl2n$2gh23$2@dont-email.me> <ohr2nkt0v3ns5i2els5u59oriaoko1cf10@4ax.com> <qgs2nk16oi9lgrgh4f2d6g3ibaibd3j1ul@4ax.com>

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On Wed, 21 Jan 2026 19:48:17 -0500, Joe Gwinn <joegwinn@comcast.net>
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:
>>>>>>
>>>>>> 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.
>
>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.
>

Our goal is to make high voltage pulses with few-ns rise and fall
times, hundreds of MHz equivalent.



John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics

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Thread

mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 08:45 -0800
  Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-21 12:28 -0500
  Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-21 12:28 -0500
    Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 10:11 -0800
  Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-22 04:49 +1100
    Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 10:18 -0800
      Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-21 23:47 +0100
        Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 16:34 -0800
          Re: mounting a pot core Joe Gwinn <joegwinn@comcast.net> - 2026-01-21 19:48 -0500
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-21 17:06 -0800
            Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-22 13:17 +0100
              Re: mounting a pot core Joe Gwinn <joegwinn@comcast.net> - 2026-01-22 12:47 -0500
                Re: mounting a pot core Joe Gwinn <joegwinn@comcast.net> - 2026-01-22 15:49 -0500
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-22 23:49 +0100
          Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-22 17:57 +1100
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 08:31 -0800
              Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-23 15:57 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 06:24 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 03:35 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 08:40 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 17:01 +1100
          Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-22 12:59 +0100
          Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-22 10:58 -0500
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 10:57 -0800
              Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-23 16:01 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 06:19 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 03:19 +1100
                Re: mounting a pot core liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2026-01-24 19:25 +0000
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-25 14:33 +1100
                Re: mounting a pot core liz@poppyrecords.invalid.invalid (Liz Tuddenham) - 2026-01-25 11:07 +0000
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-26 02:46 +1100
                Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-25 08:51 -0500
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 08:08 -0800
                Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-25 22:44 -0500
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-26 17:56 +1100
                Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-26 10:50 -0500
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-27 03:23 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 08:51 -0800
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 07:53 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-27 03:36 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 08:48 -0800
                Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-26 13:12 -0500
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-26 10:58 -0800
                Re: mounting a pot core Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-01-26 20:36 +0000
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-27 14:30 +1100
      Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-22 17:51 +1100
        Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 11:09 -0800
          Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-23 16:16 +1100
            Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 06:13 -0800
              Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-23 16:07 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 08:22 -0800
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-24 12:17 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-24 07:54 -0800
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-25 13:04 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 07:33 -0800
                Re: mounting a pot core Jeroen Belleman <jeroen@nospam.please> - 2026-01-25 17:32 +0100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 11:12 -0800
                Re: mounting a pot core JM <sunaecoNoChoppedPork@gmail.com> - 2026-01-25 19:44 +0000
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 13:07 -0800
                Re: mounting a pot core JM <sunaecoNoChoppedPork@gmail.com> - 2026-01-25 22:40 +0000
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-25 17:29 -0800
                Re: mounting a pot core JM <sunaecoNoChoppedPork@gmail.com> - 2026-01-25 19:40 +0000
              Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 03:39 +1100
                Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-23 10:09 -0800
                Re: mounting a pot core Bill Sloman <bill.sloman@ieee.org> - 2026-01-24 16:49 +1100
  Re: mounting a pot core legg <legg@nospam.magma.ca> - 2026-01-22 10:46 -0500
    Re: mounting a pot core john larkin <jl@glen--canyon.com> - 2026-01-22 11:16 -0800

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