This information should also be included in the ARRL Handbook - Ed ?
Dave - WØLEV
On Sun, Feb 20, 2022 at 8:28 PM Jim Brown <jim@audiosystemsgroup.com> 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
>
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--
*Dave - WØLEV*
*Just Let Darwin Work*
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