Topband: Thanks!

[Tom W8JI]

> These are not "excellent" 1:1 current baluns below about 75 MHz. Below 
> that range, they are a lousy common mode choke, because they are 
> inductive. Inductive chokes resonate with a line that is capacitive, so 
> they actually increase the current. A line shorter than a quarter wave is 
> capacitive; so is a line between a half wave and 3/4 wave. And so on. 
> That's why we want a choke that is highly resistive -- the resistive 
> component always reduces common mode current, which is the objective of a 
> common mode choke (the so-called "current balun.")


You may be confused, or I am. He asked about 31 mix beads:

<<<<
Hi Folks;
Thanks a bunch, to all those who responded with source possibilities for 31 
mix toroids !  I will add a note here, after I actually make a purchase to 
designate the lucky victim of my small purchase.
73 Dean  W5PJR
>>>>>>>>>>

31 materials has a Q of about 1 on 80 meters. This means a good part of the 
impedance is resistive.

While I don't beads are a good choice with large coax, only one pass can be 
made through the window with normal types of high power coax, I don't think 
the material itself is all that bad.

Also, attenuation has as much to do with grounding and wise engineering of 
common mode shunt impedances as it does choke impedance. Choke material is 
almost always a compromise between heat and Q at high power. For receiving, 
lossy common mode choke materials always work. Not so for transmitting.  One 
size will never come close to fitting all.

73 Tom