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Re: [RFI] Material 75 vs Material 31 Ferrites for EMI

To: rfi@contesting.com
Subject: Re: [RFI] Material 75 vs Material 31 Ferrites for EMI
From: Jim Brown <jim@audiosystemsgroup.com>
Reply-to: jim@audiosystemsgroup.com
Date: Fri, 10 Feb 2017 14:42:20 -0800
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
Chuck,

I looked into this half a year ago when someone asked the same question. The answer was no. I don't remember why.

Study my material on this topic. Below 5 MHz, we need multiple turns through a #31 core. Between 5 MHz and 6M, we need multiple turns through #31 or #43.

Clamp-ons of either are a waste of money and do nothing at HF.

73, Jim K9YC

 On Fri,2/10/2017 12:10 PM, Chuck Gooden wrote:

Fair-Rite has introduced a new low frequency material (#75), I was wondering if someone could comment if this new material would be better that #31 for EMI suppression. According to the Fair-rite web site, #75 shows a higher impedance at lower frequencies than #31 but above ~2 Mhz the impedance drops off. While the impedance of #31 seems to continue to increase and the frequency goes up.

I am planning on ordering some snap-it cores to reduce the noise from switch mode power supplies, and other sources, I am experiencing on HF bands. I have already read the documents on the K9YC web site but there was no info on the new material. I am tempted to stay with #31 due to it's long time use.

Thanks,

Chuck K9LC

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