[TowerTalk] Toroid Core Material Selection

[N6CW@aol.com]

Hi all,

I am always interested in toroid comments. I have been successfully cleaning 
up a lot of my long-standing RFI problems with them. My question. Ignoring the 
economics, as I have both types available, what would be the results of 
stacking one each of type 43 and 77 toroids? Would this make a toroid with the 
combined bandwidth of both and the combined choking impedance of both? And would 
this result be the same with the same two toroids in series? Type 31 material 
seems like the ultimate weapon but doesn't seem to be readily available yet.

Terry Baxter/N6CW

In a message dated 3/21/05 10:53:58 PM Pacific Daylight Time, 
W4EF at dellroy.com writes:

<< I just made some measurements 
 on a 2.4 inch O.D. type 31 Fair-Rite Products core that K9YC 
 sent me. 7 turns on this core will give you >1000 ohms choking 
 impedance from 1.8 to 30 MHz. My data shows that the 
 type 31 material is much better than type 77 material in the 
 same form factor (2.4 inch O.D. toroid). The impedance of
 the type 77 material falls off pretty rapidly above 2 MHz,
 whereas the 31 material seems to provide good series 
 impedance well past 30 MHz.  >>