[Elecraft] Toroid Balun Cores

[John Ragle]

Jim...

     I think the snap-ons are designed to be lossy devices. They are 
designed to be a convenient shape for wires, cords, cables, etc. and to 
provide loss for fields that fringe out of those cables. Tiny air gaps 
are not particularly important for this function.

     Ferrite donuts used as transformer cores are for transferring 
magnetic flux from primary to secondary without leakage.

     In a real balun, the action is as a transformer...remember those 
plug-in coils with "links" on them that Millen et al. used to make, back 
when...? Those were air-core transformers (and not very efficient...). 
The core in the balun on your beam was probably a transformer core.

     Again, 'way back when, when transformers for tube "B+" & filament 
voltages were normal parts of power supplies, the windings were on 
interleaved, laminated "E"-shaped core material. In those, working at 60 
Hz, a tiny air gap could be tolerated, even though its effect was 
somewhat like a "magnetic" resistor in the flux path. One does not see 
these as much any more, but I can remember taking them apart to harvest 
the wire inside...and being left with dozens of the laminations...

John Ragle -- W1ZI

=====

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
>>
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>
>

-- 
Sent from my lovely old Dell XPS 420