[TenTec] Ferrite Data

[Jim Brown K9YC]

On Tue, 10 Jun 2008 10:51:47 -0600, Dr. Gerald N. Johnson wrote:

>Yes the Amidon data is simplistic, yet it can be compared to Fair-rite
>data and there are 200 ham applications of Amidon ferrites to each
>published Fair-rite application. Maybe more. I don't recall seeing any
>publications calling for Fair-Rite parts.

I have, and my extensive publications on ferrite chokes for control of 
RFI and and for coaxial transmitting chokes ALL specify Fair-Rite 
toroids in specific sizes and materials. Moreover, my publications 
include MEASURED data for the performance of many of these chokes. 

But that's a marketing problem. Amidon advertises to the ham world, 
Fair-Rite does not. As far as I know, all of the ferrite parts (not the 
iron core parts) that Amidon sells are re-branded (and greatly marked 
up) Fair-Rite parts. And ham authors are often lazy -- they don't bother 
to learn that the Amidon parts are really Fair-Rite parts. That laziness 
has cost hams a LOT of money in needless markup. 

It's funny -- hams will buy $1 connectors that are junk rather than $3 
or $5 connectors of decent quality, but they'll pay $15 for the same $4 
toroid. 

>yet when applying ferrite cores for power we found at Collins that we 
>needed more data which we had to develop experimentally, by applying RF 
>power to a winding to see if the core heating was acceptable or could 
>be adequately cooled whether it took

Of course -- all of this is part of the normal engineering that must go 
into product design. The Fair-Rite catalog includes thermal data and 
saturation data for all of their materials. While this is less than what 
you measured at Collins, it goes FAR beyond anything that is published 
by Amidon. AND, the difference between the behavoir of various materials 
that you would measure in the tests you did at Collins would clearly be 
predicted by the Fair-Rite data. 

When I was working on the design of non-ovenized temperature compensated 
high stability oscillators at Motorola in in '60s, I had to make 
extensive measurements of the temperature characteristics of quartz 
crystals. Again, all part of the engineering process. 

73,

Jim Brown K9YC