[TowerTalk] Ferrites 31 vs. 77 material

[David Gilbert]

I'm sure K9YC, who knows at least 20 dB more on the subject that I do, 
will have a more thorough explanation but basically the reason is that 
Type 31 material has desirable loss at HF frequencies instead of only 
contributing inductance.  When relying only on inductance for common 
mode chokes you can get undesirable resonances that actually subvert the 
purpose of using them, whereas the loss in the Type 31 material gives 
you the low Q performance you want and it does so across a wide 
frequency range.

73,
Dave   AB7E


On 10/27/2019 11:37 AM, Bob Shohet, KQ2M wrote:
> Back ~ 2000, I was using 77 material vs. 43 material for Ferrite chokes and I constructed an impedance table by freq.to determined how many beads I should use on each band.  Now we talk about and use 31 material instead.  What I don’t recall is what happened to the 77 material and why 31 material has seemingly supplanted it.
>
> I would appreciate any thoughts/comments/comparisons on this.
>
> Tnx &73
>
>
> Bob KQ2M
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