I've found preferred method for evaluating Ferrite Choke Balun common mode rejection performance is to measure common mode rejection (CMR).
Some various 43 material examples, which demonstrate CMR is a function of device inductance. https://www.kn5l.net/Balun-CM/Balun-43material/ FT140-43 7T CMR measured using four different methods to ensure correlation and correct CMR measurement process. Also demonstrate correlation with SimSmith model using Fair-Rite Complex permeability file. https://www.kn5l.net/Balun-CM/FT140/ Comparing 31 and 43 material which demonstrate, for a given inductance, 43 material results with improved CMR. With equal turns, 31 material has small CMR improvement. https://www.kn5l.net/Balun-CM/Balun31-43/ John KN5L On 9/4/21 9:14 PM, Jim Brown wrote: > 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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
