[Elecraft] W2 directional coupler core size

[Wayne Burdick]

juergen piezo wrote:

> Elecraft seems to use very small cores for its directional coupler,  
> it does not strike me as the right size ferrite cores for a 2kw  
> meter. However I am no expert on this.  I have looked inside many  
> wattmeters  as a basis for comparison.

Hi Juergen,

Thanks for your close scrutiny of the W2's coupler. No need to worry,  
however:

The W2's cores are about the same size as the ones in the Palstar  
unit, as well as the ones we used successfully in a 1500-watt  
prototype amplifier.

These cores are operating at a satisfactory flux density as shown by  
careful modeling. They also don't get too warm to the touch when  
operated at 1500 W.  Type 61 material has a Curie temperature around  
350 degrees C, and we're not even in that ballpark, even well in  
excess of 2 KW.

73,
Wayne
N6KR