Here is an interesting article:
http://www.karinya.net/g3txq/chokes/
\Svend, OZ7UV
søn. 27. okt. 2019 21.32 skrev David Gilbert <xdavid@cis-broadband.com>:
>
> 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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