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#1 2010-12-28 08:32:51

wa2mze
Member
From: South Florida
Registered: 2009-08-22
Posts: 172

Unknown cores

I have several dozen multi-aperture cores that appear to be type BN-43-202's as they are shiny black/gray in color and about the same size.  Winding 23 turns of wire on the core and measuring the inductance (with a digital L/C meter) gives about 2050uh, (2.05mh) which doesn't match the AL factor for #43 material, or #73 or #61 either.  It's about twice the inductance that I should get (with the on line calculator) for #43 and a third that expected with #73. I wonder what this mystery material is, and what it would be good for.
My guess is that it should work as well as #43, at least below 20mhz and require fewer turns.

What inductance SHOULD a broadband transformer have on it's primary and secondary windings (assume impedances between 50 and a few hundred ohms matching) for use on the HF bands?

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#2 2010-12-29 05:38:50

W8DIZ
Administrator
Registered: 2008-08-12
Posts: 338

Re: Unknown cores

use this link to calculate inductance for an unknown toroid/binocular http://kitsandparts.com/fluxbb/viewtopi … d=601#p601
Note that binoculars made with -43 material are not spec'ed by FAIR-RITE to have a specific inductance.
I have received different versions fro fair-rite where the AL value was twice a previous versions AL value. Only the IMPEDANCE is spec'ed by FAIR_RITE
-Diz

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#3 2010-12-29 11:59:23

wa2mze
Member
From: South Florida
Registered: 2009-08-22
Posts: 172

Re: Unknown cores

W8DIZ wrote:

use this link to calculate inductance for an unknown toroid/binocular http://kitsandparts.com/fluxbb/viewtopi … d=601#p601
Note that binoculars made with -43 material are not spec'ed by FAIR-RITE to have a specific inductance.
I have received different versions fro fair-rite where the AL value was twice a previous versions AL value. Only the IMPEDANCE is spec'ed by FAIR_RITE
-Diz

Yes I remember that previous post.  I didn't realize that the AL for the bino cores was variable, so the cores I have still might just be #43 material.  My concern wasn't the inductance since I'm not using them in a tuned circuit.  However I did wonder if the inductance (and as a result the AL) would effect their performance as a broadband impedance matching transformers.  I also have quite a few of those spit core tubular ferites made for use as rf interference suppressors (1/4" or 3/8" center holes).  I also have a few that are not split cores and you have to thread the cable though them.  I think they are #43 (but could be #61).  If I epoxy them together and use them in pairs they might make nice large bino cores for broadband transistor rf power amplifiers.

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#4 2010-12-30 06:37:57

W8DIZ
Administrator
Registered: 2008-08-12
Posts: 338

Re: Unknown cores

I have found that the -43 binoculars can vary as much as 100 percent in their AL value from one manufactured lot to another.
-Diz

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