Topband: Binocular Cores

[Jim Brown]

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