Dear Peter, 

besides measuring the AL value as alrady described there is another
rather simple way to determine the characteristics of ferrites: Take an
Ohms meter and see if the core itself is conducting or not, when the
contacts touching the core are separated about half an inch or so.

Very high resistance is typical for nickel-zinc cores (suitable for rf
transformers) whilst conducting cores are of the magnesium-zinc type, to
be used at much lower frequencies.

Good luck!

73 Ha-Jo, DJ1ZB
 

"Peter Dodd" <[email protected]> schrieb:
> Does anyone know of a method of measuring the characteristics 
> (permeability) of ferrite cores?  I have a box of these most without any 
> identification although I do have T200, 68-2T and T68-2s whose 
> characteristics are known.
> 
> It occurs to me that you can make a tuned circuit and measure resonance 
> with a GDO when a ferrite core is inserted into the inductance. A graph 
> could be made of the different resonances with different cores, to 
> extrapolate the unknowns.
> 
> However I think that ferrite bulk might be a problem. For example I 
> guess the red T cores use the same material but would there be a 
> difference between the T200 and the T68?
> 
> I have lots of material about ferrites in general - I just want to know 
> what I have in my junk box. I am not interested in exact measurements, I 
> just want to know if a core is suitable for a specific job.
> 
> Regards
> 
> Peter, G3LDO
> 
> 
>