[Elecraft] Measuring Inductors (was Re: [K2] Inductivity of Toroids)

[Jack Smith]

Jim's correct - we used different terms to describe the same phenomena.

And, it should not be forgotten that even if you can characterize a 
component in a test fixture and develop an accurate model of that 
component reflecting all its manifestations, it may work differently 
when installed in the real circuit, unless the test fixture and  test 
conditions exactly duplicate the in-circuit conditions.

A simple example is the unwanted capacitance from an inductor's windings 
to the PCB surface or chassis or nearby components.

One final note about toroids - in addition to the usual inductance 
caused by windings around the core, there's a second inductive 
element--a single turn inductor formed by the windings looked at 
broadside. It's instructive to remember this effect as it can be 
responsible for unwanted inductor interaction when trying to wring out 
the last dB of stop band in a filter.

It also means the often repeated statement that a toroid is "self 
shielding" and has no external field is a questionable approximation to 
the real world. (and yes, there are other effects at work as well that 
cause toroid leakage inductance.)

Jack K8ZOA


On 1/2/2013 1:19 PM, Jim Brown wrote:
> On 1/1/2013 9:02 AM, Jim Brown wrote:
>> All real components have "stray" electrical elements due to their 
>> physical construction. 
>
> When comparing Jack Smith's ((K8ZOA) excellent and detailed post in 
> this thread, his use of "parasitic" is the same as my word "stray." 
> That is, we're talking about exactly the same thing. The difference is 
> I purposely simplified the explanation for those with less technical 
> background.  I like the word "stray" better, both because it's the way 
> I learned to talk about 60 years ago, and because it also describes 
> phenomena that is unintended.
>
> 73, Jim K9YC
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