Topband: Measuring Inductor Q

[Michael Tope]

GEORGE WALLNER wrote:

>G'day Topbanders,
>
>I am trying to measure the Q of large air would and 
>toroidal inductors. I have built a jig that I use to 
>series resonate the coil at the frequency of interest (1.8 
>and 3.5 MHz). The series C is a high Q vacuum variable. I 
>have also included a precison, non-inductive 50 ohm 
>resistor in series, and using an AIM4170 analyzer I 
>measure the Rs component, which should include the 50 ohm 
>resistor and the resistance of the inductor. (I am 
>measuring at 50 ohms because the analyzer is reported to 
>be most accurate around 50 ohms.) I get consitent results 
>to Q-s of up to about 120. I don't seem to be able to 
>measure beyond Q 120.
>
>Is there a better -- cost effective -- method I should be 
>using?
>
>TKS in advance for any advice,
>
>George
>AA7JV
>

George,

I haven't personally tried this in my lab, but the method (resistive 
divider technique) appears sound and claims to be good for inductors up 
to 400:

http://www.edn.com/article/CA196485.html

Good luck.

73, Mike W4EF