On Mon,6/8/2015 12:22 AM, Martin Kratoska wrote:
Is somewhere available a list of ferrite mixes indicating the
frequency where R=X?
Fair-Rite, a major manufacturer of ferrite materials, has extensive
technical data for their products online, FAR more than do other
manufacturers. Earlier in this thread, I posted a link to it.
http://www.fair-rite.com/newfair/materials.htm lists all of the
materials they make. Click on the link for each material to see the
technical data sheet that shows its magnetic properties.
The link for #61 material produces the following page.
http://www.fair-rite.com/newfair/materials61.htm Look at the first
graph on the left. mu's is the inductive component, mu''s is the
resistive component of the series equivalent circuit of a single turn
through the material, where mu is the multiplier in magnetic equations.
For this #61 material, those curves cross over (that is, R = X) at about
40 MHz. These data show, and the text says, that the material is good
for inductive applications (transformers, power-handling filters) below
about 25 MHz, and for EMI suppression above about 200 MHz.
Here's a datasheet for a specific part.
http://www.fair-rite.com/cgibin/catalog.pgm?THEAPPL=Suppression+Components&THEWHERE=Cable+Component&THEPART=Round+Cable+Snap-Its#select:onepart
The first graph shows the same graph of mu's and mu''s, and they cross
over at about 3.5 MHz. Now, scroll all the way to the bottom of the page
for two graphs. The first shows Rs and Xs vs frequency for a single turn
through the part. The lower graph shows the magnitude of the impedance
for one, two, and three turns. This graph shows that the impedance peaks
around 27 MHz, so three turns through this part would be a fairly
effective common mode choke on 10M. For graphs of more turns through
selected parts, see k9yc.com/RFI-Ham.pdf
Here's link to the entire catalog. It's HUGE.
http://www.fair-rite.com/newfair/pdf/Fair-Rite_Catalog_17th_Edition.pdf
73, Jim K9YC
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