[Elecraft] Choking KPA500 and testing a box of unknown chokes

[Jim Brown]

This only works at low frequencies, well below resonance of the choke 
that you've wound.  AND -- it only yields the AL value at low 
frequencies. Many materials with very different mu and mu' curves have 
similar low frequency performance. Common mode chokes are used near 
resonance, which is far more difficult to measure accurately.

There's one rather practical way to identify #31 core material with a 
simple VOM. Measuring between two points on the core on a medium to high 
ohms scale should read resistance values in the range of 50K - 200 K 
ohms, because its bulk resistivity is fairly low. Most other materials 
have much greater bulk resistivity. This characteristic is shown in a 
table on early pages of the Fair-Rite catalog (downloadable from their 
website).

73, Jim K9YC

On Mon,5/22/2017 1:08 PM, Don Wilhelm wrote:
> Mike,
>
> You may be over-thinking it.
>
> Wrap 10 turns around the core and measure its inductance.
>
> From that data, you can calculate the AL value.  Match that AL value 
> against a chart of the values for various cores.
>
> 73,
> Don W3FPR
>
> On 5/22/2017 9:30 AM, Michael Walker wrote:
>> All
>>
>> I am doing some work on a box of chokes I received and I am trying to
>> figure out just exactly what mix they are.
>>
>> I have a tracking generator, so I am trying to figure out  a test 
>> jig.  Do
>> I just wrap the choke in fleedline, have a common ground and then use 
>> the
>> shield of the feedline to feed my signal over looking for the 
>> attenuation
>> on the receiving end of the generator?
>>
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