[Amps] Amps Digest, Vol 264, Issue 7

[john simmons]

Jim,

Thanks from all of us for your generous free publications! Whenever the subject of EMI/RFI comes up I *ALWAYS* refer to your papers.

73
-de "Curly" John NI0K
QRZ.com<https://www.qrz.com/db/ni0k>
Hamshack Hotline<https://hamshackhotline.com/> call me: 6100271
On 12/6/2024 12:24 PM, Jim Brown wrote:

Ferrites work for RFI suppression BECAUSE of their parallel self resonance, and the chemistry of each mix determines both where that resonance occurs and it's usefulness in suppression. NiZn chemistries (for example, Fair-Rite #43, #52, #61) provide a single resonance, usually fairly high-Q; MnZn chemistries (Fair-Rite #31, #75, #77, #78) provide two, one based on windings, the second based on cross-sectional area of the flux path. Fair-Rite's #31 is unique -- it's dimensional resonance in convenient sizes lands in a sweet spot for HF IF, and ONLY IF, turns are wound through it.

There's a lot more of what I've learned about this over 20 years of study in k9yc.com/RFI-Ham.pdf  and in the 2018 Choke Cookbook at k9yc.com/publish.htm  I began this study in 2004 to address RFI to large sound systems and published it as an AES Paper in 2005. I first published RFI-Ham.pdf, which addresses its applications to ham radio, in 2007.

73, Jim K9YC



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