Hi guys:
Read this especially the passage about #43 material:
Following is a list of large size Ferrite Beads (FB), Ferrite Toroidal Cores
(FT), and Split Ferrite Cores (2X), all of which are extensively used for
RFI problems involving multiple wire bundles, coaxial cables, microphone
cables, AC cords and computer ribbon cables. These larger ferrite beads and
toroidal cores can provide larger ID to accommodate the larger diameter
coaxes and wire bundles.
The 43 material is a good all around material for most RFI problems.
However, the lower frequencies from .5 to 10 MHz can best be served with the
'J' material. The 77 material can provide excellent attenuation of RFI
caused by amateur radio frequencies from 2 to 30 MHz and the 43 material is
best for everything above 30 MHz. However, it is still very effective across
the entire amateur band but not quite as good as the 77 materials. The 73
material is specifically a ferrite bead material having a permeability of
2500 and can provide RF attenuation very similar to the 77 core material.
When more impedance is needed (with any bead or core) use additional cores
on the same conductor or a core with a large enough ID to accommodate
multiple wire turns. When additional cores are added, the impedance will be
additive, but when additional wire turns are added the impedance increases
to the number of turns squared.
Split beads and 'bars' are also available to that they may be installed
without removing the end connector from the cable. Split bars are especially
designed for computer ribbon cables. They are presently available for 1.3",
2.0" and 2.5" computer ribbon cables. Two or more may be used on the same
cable to increase the impedance.
Shown below are typical impedances in ohms at 25 and 100 MHz with only one
pass through the core.
These materials are intended for RF SUPPRESSION not RF transfer. They
convert RF to heat by a mechanism of internal loss: they are conductive and
have relatively high Ur.
What you should look for are min #2 -red cores- from Micrometals. They are
intended for use as RF transformers from 500kHz to about 2MHz. Epcos
(formerly Philips), Ferroxcube, Tomita Electric and Micrometals make them.
Alex 4Z5KS
(table/diagram)
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of sasas asasas
Sent: Sunday, April 18, 2010 6:01 PM
To: amps@contesting.com
Subject: Re: [Amps] 160m mosfet linear amplifier problem with ferrite cores
i think that the proper material is 43 or 77 for frequences between 1-2mhz.
i search in some internet sites and i found these:
31 Material
A MnZn ferrite designed specifically for EMI suppression applications
from as low as 1 MHz up to 500 MHz. This material does not have the
dimensional
resonance limitations associated with conventional MnZn ferrite materials.
Round cable EMI suppression cores, round cable snap-its, flat cable EMI
suppression
cores and flat cable snap-its are all available in 31 material.
43 Material
This NiZn is our most popular ferrite for suppression of conducted EMI
from 20 MHz to 250 MHz. This material is also used for inductive
applications such
as high frequency common-mode chokes. EMI suppression beads, beads on
leads, SM beads,
multi-aperture cores, round cable EMI suppression cores, round cable
snap-its,
flat cable EMI suppression cores, flat cable snap-its, miscellaneous
suppression cores,
bobbins, and toroids are all available in 43 material.
So, the 31 material supresses frequences from as low as 1 MHz up to 500 MHz!
So, i think that is not suitable for 1-2mhz operation. What do you
believe????
Also see here: http://users.catchnet.com.au/~rjandusimports/ft_mat_1.html ;
<-- you can see that 43 or 77 material is suitable for 1-2mhz frequences.
For 31 material no one refer.
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