[TowerTalk] Measuring Common Mode Choke with Anritsu VNA
jim at audiosystemsgroup.com
Wed Jan 3 12:53:33 EST 2018
Exactly right! NA6O reported exactly the same comment to me in private
email. Z is not a single-valued number, it is a variable and it is complex.
I'm currently in the middle of a project measuring chokes wound on the
relatively new double-sized #31 toroid, and an important thing I'm
learning is that the "double-humped" curve shape that results from
dimensional resonance in the range of 3-5 MHz disappears below that
range. In addition, the loss component also falls at lower frequencies,
so as a result, chokes wound to cover 160M, for example, exhibit much
higher Q, and thus much narrower bandwidth. I'm currently looking for a
different ferrite mix whose loss vs frequency characteristics are
optimized a decade lower in frequency for use on the LF bands.
73, Jim K9YC
On 1/2/2018 9:59 PM, Jeff Blaine wrote:
> The issue is not the value of the actual Z. The issue is that the
> reported peak Z frequency can be very far removed from the true value.
> Hence the problem. If you build a monster Z choke but it's narrow
> banded, then the measurement error (with respect to frequency of the
> peak) is important.
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