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[RFI] RFI Hints

To: <rfi@contesting.com>
Subject: [RFI] RFI Hints
From: tduffy <tduffy@sygnet.com> (tduffy)
Date: Wed, 25 Mar 1998 11:41:56 -0800
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Subject: It may not be ferrite; but...
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In-reply-to: <m0yHYNB-000ZmwC@mgate.arrl.org>


   Probably nothing new, but original for me.

   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 
have worked well for me. Multiple passes of the cable are possible to achieve 
high isolation reactance and the power handling capabilities for brute force 
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.

   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 
  

  The meek will not inherit the Earth. 

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