[Elecraft] Bad Ham Radio Day

[Jim Brown]

On 9/4/2021 2:48 PM, jerry wrote:
> 31-mix is supposed to be the hot ticket for HF common mode
> chokes.  One turn through one core is supposed to be 98 ohms at 5MHz. So 
> four cores should give me about 400 ohms, which should give a worthwhile 
> attenuation in a 50 ohm system.  Thanks for the references.

I'm the guy that did the original work on this, beginning in 2003, when 
#31 was a brand new mix. I got five of the first #31 toroids from the 
pre-production run, a few months after I suggested that they would be 
quite useful. My first publication was a paper to a 2005 international 
meeting of the Audio Engineering Society, of which I'm a Fellow. First 
publication to the ham world was RFI-Ham.pdf in 2007. And you are 
mistaken about the value of four cores at HF. Study that paper. It's a 
tutorial on how RFI happens and how chokes work.

73, Jim K9YC