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From: john larkin <jlArbor.com>
Newsgroups: sci.electronics.design
Subject: Re: Binocular choke extras
Date: Fri, 21 Mar 2025 07:46:18 -0700
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On Thu, 20 Mar 2025 12:39:43 -0400, legg <legg@nospam.magma.ca> wrote:

>On Wed, 19 Mar 2025 23:24:36 +0100, Jeroen Belleman
><jeroen@nospam.please> wrote:
>
>>On 3/19/25 22:40, Liz Tuddenham wrote:
>>> I've just taken delivery of a couple of ferrite 'binocular' choke cores;
>>> each one came with two thinwalled metal tubes and some bits of printed
>>> circuit board.  The tubes appear to go through the holes in the choke
>>> and the holes in the boards fit over the ends of the tubes, with copper
>>> areas that could possibly be soldered to them.
>>> 
>>> Does anyone know what purpose these serve?
>>> 
>>> 
>>
>>This sounds very much like the transformers used in wideband RF
>>power amplifiers. See for example Helge Granberg's application
>>note 762. The tubes with a piece of circuit board form the single-
>>turn low impedance winding, and a number of turns of insulated
>>copper wire going through the tubes form the high-impedance
>>winding. This makes for a good coupling factor and consequently
>>good wideband operation.
>>
>><https://www.communication-concepts.com/content/AN762/AN762_Application_Note.pdf>
>>
>>Jeroen Belleman
>
>Can also be used in directional couplers and baluns, which I suppose 
> are just high frequency transformers by another name.
>
>RL

Some people enjoy calling txline transformers "ununs" when neither end
is a balanced load against ground.

Is there a balbal?