[K6BW] Did You Know? The permeablity in ferrite type 43 cores is not consistent.

[Bill Smith]

>From the QRP-L reflector...  The ferrite mix in type 43 can vary
significantly.

>From an N4QA post on 3 May 2008, subject line "Opinions sought for a
particular
LCR bridge"-

>.I do use Diz' neat [toroid] calculator..I wound 48 turns onto an FT50-43
>core and took it to work to measure it on the Gen-Rad LCR bridge at 1 KHz.
>The measurement was 50% high....Removing 9 turns (leaving 39 turns) yielded
>a measurement of 970 uH. how could Diz' calculator be so far off?

It's probably not off; it's most likely the large variation in the
characteristics of the type 43 material, something I just learned about.

Forgive me if this has already been posted here; I haven't been watching the
list too closely of late. In late March on another QRP list, W8DIZ posted
the following info about type 43 material. I asked him if I could repost it
to this list and he agreed. That was weeks ago and I never got around to
doing it. If someone else did, I apologize for repeating this.  The basic
premise is that type 43 material is not a precision mix and you can't put
too much stock in the published permeability or Al values for this specific
material.

The W8DIZ post to another QRP list on 18 March 2008--

"Not too long ago, I purchased a large quantity of BN-43-202 binoculars from
Fair-Rite. [When Diz says large, he means large. He is a serious trafficker
in ferrites and powdered irons, running a home business selling them to
homebrewers.] The parts measured 220 uH per 10 full turns which gives them
an AL value of 2200.

"Last month, I ordered another large quantity of the same part. I noticed
that the part looked slightly different, not as bright and shiny; so I
tested a few pieces. Ten turns for the newer binoculars measured 380 uH. I
was expecting maybe +/- 20 percent tolerance variances but this was a bit
much.

"So I talk to a Fair-Rite application engineer and he tells me that they do
not even measure inductance for the type -43 material. They do not publish
an AL value for -43 material ferrites.

"Note that Fair-Rite (who supplies me and other vendors such as Amidon)
farms out their parts manufacturing to different companies. In the past,
most of their products were manufactured in the USA. Now their packages
state "MADE IN CHINA"; and even from China, I've seen huge variations, both
physical and electrical, in the same product.

"So, do not expect type -43 material ferrites to be consistent. Just a heads
up.

"PS: Note that Fair-Rite DOES publish AL values for -61 material parts."

When Diz gave his permission, he also made these comments-

"There are other distributors of FAIR-RITE parts that publish the AL
values of -43 parts, but the AL values did not come from FAIR-RITE.
In my case, I just measured 2 or 3 samples and published the results. "

Although Diz reported on binocular cores, it is probably reasonable to
expect that all forms and sizes of the type 43 material from a given
manufacturing plant will have the same characteristics. (And remember that
Fair-Rite apparently has manufacturing done by a number of different
factories.) The bottom line appears to be that you can't really count on the
actual permeability or AL value of type 43 material, at least when it comes
from Fair-Rite.

73 and queue our pea DE WA8MCQ