>From: "pmarkham" <pmarkham@ns1.lagasco.com>
>To: rfi@contesting.com
To: <rfi@contesting.com>
>Date: Thu, 26 Mar 1998 11:00:44 -0005
>Subject: It may not be ferrite; but...
>I use deflection yoke cores from junk tvs to decouple feedlines, power
>supply leads, computer cables, etc. They are bulky, even from a small tv,
but
>isolation has merit.
> As for material type, technical characteristics and efficiency; it is no
>concern to me as the cores are free and work for my various applications.
This often works, but the ferrite material was designed for 15 kHz; its
characteristics at RF are unknown. The only risk to this is that it may not
work, and you may be mislead into thinking a common-mode choke would not
have solved your problem, where, in reality, a choke made of the proper
material for the frequency involved may have worked just fine.
73 from ARRL HQ,
Ed Hare, W1RFI
ARRL Lab
> I strip off the plastic and wire, and save the clips or clamps that hold
the
>halves together. I then reassemble the core assembly, using the clamp
hardware
>or long nylon tiewraps or electrical tape. I then wrap the sharp edges with
>good quality tape. I wrap my flexible cable through the assembly as
desired. I
>assemble them around my hardline, as I get them, as a stack of large
'beads"
>They can be used indoors and out.
>My open wire fed 75 m dipole passes over the shack, some 30' above. My
>shunt fed tower is 3 feet away from my equipment. I operate hf, vhf and uhf
>with the typical 50 to 100 watt levels with no rf related gremlins in
>the shack. I sometimes run the legal limit on hf and operate the computer
at
>the same time, without grief. As for most folks my rf ground system is
poor
>but extensive cable "choking" has enabled me to operate all mode, analog
and
>digital with virtually no grief.
>They are quite effective for killing emi radiating from scr and triac
>controller power cords, swiching power supplies, etc. They have never
failed
>to keep rf out of my power supplies, when all leads were choked with a
core.
>Touch control lamp cord "choking" has been very effective. I have used them
>for eliminating rfi in telephones, vcrs, stereos, tvs, blah, blah, blah.
> I have never checked to see how conductive they are to the typical dc
and ac
>voltages used in the shack. You are warned!
> I am sure, for those that wish to give my suggestion a whirl, there will
be
>many happy customers, but as always, your milage may vary. Posted details
of
>successful problem resolutions with similar or described techniques might
>be of value to others.
> Pete/wa4hei
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