Re: Topband: RX antenna transformer winding (pure resistance transformation issues)

[Jim Brown <jim@audiosystemsgroup.com>]

On 8/20/2013 1:00 PM, Tom W8JI wrote:
> By squeezing or spreading turns to change mutual coupling between 
> turns, a T157-2 core can have almost 2:1 impedance shift! That tells 
> us it has considerable flux leakage. 
So-called "self-shielding" and it's inverse,  leakage flux, also depend 
on permeability, which in turn depends on the material and the frequency 
of interest. Fair-Rite data sheets for their materials clearly show the 
variation of permeability with frequency.
And when we squeeze or spread turns we are also changing stray C of the 
winding.
73, Jim K9YC
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Topband Reflector