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

[d.cutter at ntlworld.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 at 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.
>