[TowerTalk] Measuring Ferrite

Jim Lux jimlux at earthlink.net
Thu Apr 10 23:47:35 EDT 2014

On 4/10/14 2:38 PM, Jim Brown wrote:
> On 4/10/2014 1:58 PM, Earl Morse wrote:
>> I confess, I am spoiled.  I have access to a plethora of RF devices
>> such as network and impedance analyzers so I wouldn't have to make do
>> with making this measurement with a rigged up setup.
> Actually, measuring ferrite chokes is not nearly as easy as it looks.
> The only stand alone instrument I would trust the the HP impedance
> analyzer. All reflection-based analyzers have the limitation of greatly
> reduced accuracy as the impedance is much more than 1/5 or 5x the
> circuit Z. There are HP applications notes that address this issue.

True, if you want to characterize, but if you're in the "sorting by mix" 
mode, I think a lot of fairly simple test equipment can do the job. 
You're looking for mu changes of a factor of 5 or 10, and you can pick 
frequencies which work well.

For checking whether that mix 43 binocular core is within spec.. not a 
chance with cheap and cheerful.

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