[RFI] Fair-rite Toroids verses Round Cable Suppression Cores

[Jim Brown]

On Thu,2/5/2015 10:55 AM, Wm.Glenn Pearson wrote:
> I am in the process of acquiring a supply of type 31 ferrites. Should I
> replace my previously purchased toroids with the type 31 equivalent
> (2631803802)?

Study my tutorial. k9yc.com/RFI-Ham.pdf

The short answers are:

1) Yes, you should. #31 material is significantly better than #43 below 
5 MHz, and nearly as good as #43 above 20 MHz. It is one of Fair-Rite's 
newer materials, first appearing in their catalog around 2003. I tested 
some of the first #31 toroids around 2004, when they were not yet in the 
catalog. I suspect, but I am not certain, that they started making the 
toroids because after testing other #31 parts, I asked for toroids. :)

2) #43 material is a bit cheaper (10-20%) than #31 for the same 
quantities, but if you buy more pieces of #31, the cost will be about 
the same as for splitting the order between the two parts. I've done and 
assisted with several group purchases, and I've always bought only #31 
material.

3) Fair-Rite sells #43 toroids both as "suppression" parts, where they 
specify and control the impedance vs frequency, and as "inductive" parts 
where they specify and control the inductive behavior at low frequencies 
where the material is not very lossy. That's why there are two part 
numbers for #43 toroids. Suppression works BECAUSE the part is lossy, 
and USES the loss component of the core.

73, Jim K9YC