[Elecraft] Toroid Balun Cores

[Vic K2VCO]

Some confusion results from the fact that there are two different materials used in 
toroids (etc.): Ferrite and powdered iron. Powdered iron cores are composed of tiny 
particles which are insulated from one another...so if they break you can glue them back 
together and they will work fine.

Ferrite is a ceramic material, and if you glue a broken piece of ferrite back together you 
are introducing an insulating gap which breaks the magnetic circuit. Powdered iron is a 
bunch of little magnets separated by gaps already.

Baluns seem to be made out of ferrite.


On 10/16/2011 3:13 PM, Jack Smith wrote:
> First, even a very thin gap may significantly reduce the core
> permeability. A high quality split core will have its mating surfaces
> lapped flat.
>
> Second, if the core cracked because of excessive heat, it's likely the
> ferrite material incurred irreversible damage.
>
> Jack K8ZOA
>
>
> On 10/16/2011 5:58 PM, Jim Wiley wrote:
>>
>> OK, now I am confused (a normal state of affairs around here)
>>
>>
>> If a "cracked" toroid core is useless,  then how do the "split bead"
>> clamp-on cores manage to work?  Isn't the "split" equivalent to as great
>> big lengthwise crack?
>>
>>
>> I also seem to remember broken ring cores working again when glued
>> together.
>>
>>
>> After all, isn't a ferrite core itself manufactured from ferrite powder
>> that has been "glued together" by a binding material?  Yes, the
>> particles are pressed very close to one another,but they are still
>> individual particles, are they not?
>>
>>
>> - Jim, KL7CC
>>
>>
>>
>> John Ragle wrote:
>>> <snip>
>>>
>>> I agree with the contributor(s) who said that the cracked toroid is
>>> basically junk. It has lost its utility because the magnetic circuit is
>>> broken at the crack. It is unlikely that superglue will restore it.
>>>
>>> John Ragle -- W1ZI
>>>
>>>


-- 
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/