[RFI] Material 75 vs Material 31 Ferrites for EMI
Jim Brown
jim at audiosystemsgroup.com
Fri Feb 10 17:42:20 EST 2017
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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