>Rich said:
>
>> It is a broadband, ferrite toroidal-core,
>>transformer that triples the RF driving V for the grid. Twisting the
>>bundle of 4 wires prior to winding reportedly improves bandwidth.
>
>A lot depends on whether you go for a conventional transformer in which energy
>is transferred through the core, or a transmission line transformer where the
>core has a common mode suppression function. Worth getting Sevick's
>'Transmission Line Transformers' book. It used to be published by ARRL, but I
>believe it's now published by someone else. Certainly the techniques in
>transmission line tranformers use twisted wire transmission lines, and they
are
>capable of very wide bandwidths.
>
// It's a transmission-line wound on a Mu=40, 61mm ferrite toroid.
Unlike (lower-Mu) powdered iron, (higher-Mu) ferrite has the tradeoff of
being subject to saturation above a finite number of Webers/cm^3 and MHz.
- The fly in the ointment with Sevick is that he tests his designs with
low power. For example, Mu=125 ferrite material has a 10MHz rating,
however, it works well at 29MHz with low power. With more power, it
saturates.
- This transformer needs to work at >150W. I am not a QRP-devotee.
cheers, Peter
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,
www.vcnet.com/measures.
end
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