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General => General Technical Chat => Topic started by: mzdenkov on June 17, 2014, 07:42:44 pm

Title: Need Help! ( ferrite core )
Post by: mzdenkov on June 17, 2014, 07:42:44 pm
Hello!

So as I said in subject name, I need help.
Recently I've opened some old and not working  AM/FM radios and i found some
ferrite cores/rods like this one on pic. :
http://upload.wikimedia.org/wikipedia/commons/6/62/Ferrite_antenna.jpg (http://upload.wikimedia.org/wikipedia/commons/6/62/Ferrite_antenna.jpg)

So can someone tell me or link me the datasheet of this? because im having some
ideas to use them in some projects, but the problem is that I dont know the characteristics of that
rods and that makes some problems while doing some calculations for the coils, etc.


Thanks!
Title: Re: Need Help! ( ferrite core )
Post by: gibbled on June 17, 2014, 08:36:50 pm
This might get you started...

http://www.amidoncorp.com/rods-and-tiles/
Title: Re: Need Help! ( ferrite core )
Post by: mzdenkov on June 17, 2014, 09:37:08 pm
Hmmm, thanks... i will give it  a try. They only give  frequnecy interval where the rods work, but not the magnetic properties of the rod (magnetic loss, B/H (Magnetic Hysteresis) properties).

Now at least i have a clue where to look.

Thanks!
Title: Re: Need Help! ( ferrite core )
Post by: T3sl4co1l on June 17, 2014, 11:49:23 pm
Impossible to say exactly.

Without taking measurements, it's very likely it's:
MnZn ferrite
mu >= 500
Fo > 1MHz
Bmax >= 0.3T

Further, it might be very similar to a Fair-Rite #77 (generic all-purpose, mu=2000), or #33 (lower mu, near zero tempco).

It's unlikely to be very high mu (doesn't matter a damn for a rod; low cutoff frequency), or NiZn (lower Bmax which won't matter, but higher cost and lower mu will matter).

If you want more, Amidon does indeed have #33 rods in various sizes.

Tim
Title: Re: Need Help! ( ferrite core )
Post by: mzdenkov on June 18, 2014, 02:11:28 am

MnZn ferrite
mu >= 500


Can you tell me for what "mu" stands for?
Title: Re: Need Help! ( ferrite core )
Post by: Rigby on June 18, 2014, 02:13:30 am
In context, guessing, it looks like a magnetic permeability measurement.
Title: Re: Need Help! ( ferrite core )
Post by: T3sl4co1l on June 18, 2014, 03:03:14 am
Yes, relative permeability.

Needless to say, you need formulas that use mu, to calculate anything.  Example:
(http://seventransistorlabs.com/Images/Rod_Core_Pressman_Billings_Morey.png)

Tim
Title: Re: Need Help! ( ferrite core )
Post by: mzdenkov on June 18, 2014, 04:08:20 pm
I know about forumulas, because i have used them on one or two college courses, but they are a little bit
diffirent.