[RFI] Can you combine two mixes?

[Jim Brown]

On 12/15/2025 4:44 PM, BOB WATWOSQQ wrote:
> If I want to broaden the operating frequency of a common mode choke, can
> you stack two different mixes, say a 31 and a 43 to create one common choke?

My many years of research yielded a Cookbook that includes a table of 
designs that use multiple chokes in series all on Fair-Rite #31 cores, 
to provide wider choking bandwidth and greater power handling.

I do NOT find #43 or other NiZn cores useful on HF because of their 
higher Q and the wide manufacturing tolerances associated with all 
ferrite products.

My designs are for use in coaxial or 2-wire transmission lines made with 
insulated wire touching each other, feeding antennas that are reasonably 
well matched the the line. The Zo of that 2-wire line is close to 100 
ohms. The chokes are most effective at the feedpoint.

While they can be used at the feedpoint of antennas that are NOT 
resonant at operating frequencies, their power handing capability is FAR 
lower. Power handling is even worse for off-center fed antennas.

The Choke Cookbook is http://k9yc.com/2018Cookbook.pdf
The tutorial is http://k9yc.com/RFI-Ham.pdf

My website is k9yc.com/publish.htm

73, Jim K9YC