[TowerTalk] ferrites for Beverage transformers

Jim Brown jim at audiosystemsgroup.com
Wed Apr 12 13:10:03 EDT 2017

No.The first two digits in the part number indicate the application for 
which the part is intended, and for which it is tested to meet published 
specs. You can, for example, buy toroids of the same material and 
physical dimensions that are tested as inductive components that carry 
one part number and those tested as suppression components with a 
different part number. #61 material is sold as an inductive part for use 
at HF and as a suppression part for use at UHF. ALL ferrite parts have 
this behavior and application -- the difference between one mix and 
another is where in the frequency spectrum this transition takes place. 
That's why I could use #43 cores, designed for suppression at VHF to 
wind inductive components (transformers) for 2-4 MHz.

The second two digiits indicate the mix -- the chemical composition of 
the material, and thus its electrical properties. The last two digits 
indicate its finish. 02 indicates that it is burnished to eliminate 
sharp edges.  The intermediate digits indicate form factor.

I don't understand the reluctance to go to Fair-Rite's website, download 
and study their catalog. In my 50+ years as an EE graduate and much of 
it a working engineer, Fair-Rite's technical data is among the top half 
dozen companies EVER, ranking with companies like RCA, TI, ElectroVoice, 
and National Semiconductor in the detail they provide about their 
products. It is possible to actually LEARN by STUDYING the Fair-Rite 
catalog. Assuming, of course, a basic understanding of the fundamentals.

Material specs begin on page 10. Page 30 describes #73 material. A quick 
study of the first graph of complex permeability vs frequency shows that 
it is a poor choice as an inductive component above 1 MHz. Why it has 
become popular for Beverage transformers is a mystery to me. The only 
logic that comes to mind is "monkey see, monkey do." Indeed, W2DU 
CORRECTLY chose this material for his "string of beads" common mode 
choke that he called a "current balun," because is it quite lossy in the 
HF spectrum.

73, Jim K9YC

On Wed,4/12/2017 6:28 AM, David Robbins wrote:
> That fair-rite product number comes back to a multi-aperture core kit that
> has 5 sizes of 4 different materials... has fair-rite maybe changed their
> product numbering since some of those pages have been written??

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