[TowerTalk] Ferrites 31 vs. 77 material

[Bob Shohet, KQ2M]

Thank you Dave and Svend!

73

Bob  KQ2M


From: Svend Spanget 
Sent: Monday, October 28, 2019 12:13 AM
To: David Gilbert 
Cc: Towertalk 
Subject: Re: [TowerTalk] Ferrites 31 vs. 77 material

Here is an interesting article:
http://www.karinya.net/g3txq/chokes/

\Svend, OZ7UV


søn. 27. okt. 2019 21.32 skrev David Gilbert <xdavid at 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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