[TowerTalk] Baluns/tutorial/notes.

[Jim Brown]

On Sat, 22 May 2010 15:08:50 +0100, Steve Hunt wrote:

>Given the importance of having resistive (lossy) chokes, I wonder how 
>you determine the phase angle using your test set-up?

I showed that in my tutorial. I plot the curve of Z vs frequency, then do 
curve fitting for the parallel resonant circuit to get values of R, L, 
and C. Not as elegant as a VNA, but it works. :)  This works for #43 
(NiZn) without modification, but for #31 (MnZn), which can have two very 
broad resonant peaks with a lot of turns, one must attempt to fit two 
curves, one on the low end and one on the high end. The result is a very 
rough approximation. See the early section of the tutorial where I showed 
that the equivalent circuit is two parallel resonant circuits in series, 
showed that some materials have both, some have only one, and then 
compared #43 with #31. 

As a very rough approximation, we can assume that the choke is 
predominantly resistive if the Z is within about 30% of its peak value. 

73,

Jim K9YC