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Re: [Amps] 160m mosfet linear amplifier problem with ferrite cores

To: alexeban <alexeban@gmail.com>, amps@contesting.com, 'sasas asasas' <tzitzikas_ee@yahoo.com>
Subject: Re: [Amps] 160m mosfet linear amplifier problem with ferrite cores
From: <d.cutter@ntlworld.com>
Date: Mon, 19 Apr 2010 13:09:47 +0100
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Alex

I'm not sure if you would call 500W 'high power' - I would from a UK 
perspective.  In the classic EB104 I see ordinary transformers.  Perhaps I'm 
not understanding something, you're the expert. Where is the crossover from 
flux coupled transformers to transmission line transformers? 

David
G3UNA

---- alexeban <alexeban@gmail.com> wrote: 
> Guys, the problem is more pernicious than that!
> 
> The problem is in the way the transformers are WOUND!
> 
> Efficient high power transformers are wound using transmission line
> coupling, not flux link coupling; they use coaxial line windings, with a
> very specific Zo. This technique ensures very tight coupling between primary
> and secondary, thus relieving the core from carrying high magnetic flux. The
> ferrite only serves to increase the reactance of the windings at the lower
> frequency end. Actually ferrites with a Ur of about 125 are sufficient in
> the HF range.
> 
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