FairRite has an excellent presentation on determining ferrite toroid
material. All that's required is some method of measuring both the
physical dimensions of the toroid (a ruler or calipers) and the inductance
at low frequency (100 to 300 kHz) of 10 or so turns of wire on the toroid.
This and many additional "goodies" can be accessed at the following URL
(scroll down for the ferrite material determination tutorial):
https://www.fair-rite.com/videos-presentations/
I've used this quite successfully over the last year. It's golden in
determining unknown toroids bought at a hamfest. Also, the distinction
between 31 (general low frequency) and 43 (generally high frequency)
material is easy. 43 material consists of NiZn and has an extremely high
bulk resistivity - above the reach of most DMMs. 31 material consists of
MnZn and exhibits relatively low bulk resistivity - easily measured by any
good DMM. Other than that, refer to the online FairRite video.
Dave - WØLEV
On Sun, Feb 20, 2022 at 12:13 PM Hare, Ed, W1RFI <w1rfi@arrl.org> wrote:
> The DM filter is conventional, with L and C.
>
> The ground lead is passed through a toroid with about 10 turns of wire.
>
> The toroids are not marked, so it will not be certain what material they
> are."
>
> Ed
>
> ------------------------------
> *From:* RFI <rfi-bounces+w1rfi=arrl.org@contesting.com> on behalf of
> Edward Mccann via RFI <rfi@contesting.com>
> *Sent:* Friday, February 18, 2022 6:41 PM
> *To:* David Eckhardt <davearea51a@gmail.com>
> *Cc:* rfi@contesting.com <rfi@contesting.com>
> *Subject:* Re: [RFI] Solar panel RFI
>
> Dave-
>
> Any details or pictures on your three lines of the main CM choke?
>
> One choke for each line?
>
> A simple multiple wrap of the power cord?
>
> Thanks,
>
> AG6CX
>
>
> Sent from my iPhone
>
> > On Feb 18, 2022, at 3:19 PM, David Eckhardt <davearea51a@gmail.com>
> wrote:
> >
> > An effective common mode choke on the mains conductors should pass all
> > three conductors through the core. For a 2.4-inch OD core, three turns
> are
> > usually good. Too many more will increase the capacitive coupling. 31
> > material has an advantage at the lower frequencies where the older 43
> > material is a bit better at higher frequencies. All referring to HF.
> >
> > I have "solved" many an emissions problem usually around 40 to 70 MHz
> from
> > SMPSs by simply installing a simple common mode choke on the mains lines
> > (yes, all three lines: hot, neutral, and "ground" - the green wire).
> Once
> > these products reach a contract manufacturer, the common mode choke adds
> > nothing to performance and only adds cost, so it is removed. Many times
> I
> > ran into the reality that contract manufacturers are the EMC engineer's
> > worst enemy. They are supplsed to retest and re-qualify, but they don't.
> >
> > Dave - WØLEV
> >
> >> On Fri, Feb 18, 2022 at 10:51 PM Jim Brown <jim@audiosystemsgroup.com>
> >> wrote:
> >>
> >> Thanks Ed. What ferrite mix and how many turns?
> >>
> >> 73, Jim K9YC
> >>
> >>> On 2/18/2022 12:53 PM, Hare, Ed, W1RFI wrote:
> >>> We just obtained an AC line filter by Morgan Manufacturing. It also
> used
> >>> a ferrite on the ground wire.
> >>
> >> _______________________________________________
> >> RFI mailing list
> >> RFI@contesting.com
> >> http://lists.contesting.com/mailman/listinfo/rfi
> >>
> >
> >
> > --
> > *Dave - WØLEV*
> > *Just Let Darwin Work*
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
>
> _______________________________________________
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>
--
*Dave - WØLEV*
*Just Let Darwin Work*
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