Nothing fancy. I'll attach an image of the test fixture I use. It is not
appropriate for frequencies much above 54 MHz, but works fine for HF on
downward. In determining ferrite material, one does not need coverage
above even 10 MHz.
Dave - WØ LEV
On Sun, Feb 20, 2022 at 10:48 PM Dave (NK7Z) <dave@nk7z.net> wrote:
> Jim,
>
> That is most interesting material, thank you! Will you all be including
> a test fixture description as well? I am in the process of gathering
> the materials to build a test fixture, and would like to see your
> designs...
>
> 73, and thanks,
> Dave (NK7Z)
> https://www.nk7z.net
> ARRL Volunteer Examiner
> ARRL Technical Specialist, RFI
> ARRL Asst. Director, NW Division, Technical Resources
>
> On 2/20/22 12:28, Jim Brown wrote:
> > On 2/20/2022 4:13 AM, Hare, Ed, W1RFI wrote:
> >> The toroids are not marked, so it will not be certain what material
> >> they are."
> >
> > Thanks. For the next Handbook, I've given Ward details of a method to
> > identify a few MnZn ferrite materials with an ohmmeter. It was first
> > suggested by W1HIS, and I fleshed it out a bit further. It's pretty
> > simple. It worked with the three VOMs in my lab -- a Simpson 260, a
> > Fluke 8060A, and a nice little no-name digital VOM that I bought for
> > about $15 at a northwest Indiana hamfest at least 20 years ago.
> >
> > With the meter on a high range scale, aggressively scratch the surface
> > of the ferrite with the probes so that they get through the coating, and
> > note the reading, if there is one. #31, #75, #77, and #78 are MnZn
> > mixes, and will show a reading in the range of 100K - 700K; #75, #77,
> > and #78 will be in the range of 1K - 10K. #43, #52, and #61 -- are NiZn
> > materials, which have MUCH higher bulk resistivities, and will show no
> > conductivity at all. These resistivity values, as well as initial
> > permeabilty (mu at low frequency) are tabulated in early pages of the
> > Fair-Rite catalog.
> >
> > We're also including methods to zero in on the specific material
> > measuring inductance using traditional methods or studying the shape of
> > an impedance sweep with a well calibrated Vector Analyzer.
> >
> > These methods, of course, depend on knowing AL or ui values for the
> > various materials. Fair-Rite's published data is FAR more extensive than
> > any other manufacturers; others publish little more than marketing or
> > limited applications data. For example, Laird (used to be Steward)
> > publishes ui values for only two of about eight materials.
> >
> > 73, Jim K9YC
> >
> > _______________________________________________
> > RFI mailing list
> > RFI@contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
> _______________________________________________
> 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
|