[CQ-Contest] RFI in PC Monitors

[Eric Scace]

I have had good success reducing RFI from the signal cable between the PC
and the monitor as follows:

-- using an old piece of RG-213 or equivalent coax cable of length equal to
the monitor signal cable length, strip off the outer insulation.  Slide the
braid (shield) off of the coax.
-- remove the connector from the PC end of the signal cable.  Some cables
have molded-on connectors, so your only choice will be to cut the connector
off.
-- slide the braid over the signal cable.
-- slide ferrite beads with adequate hole size over the braid+cable and glue
in place at the PC-end of the signal cable.  I have used 2 beads that were
about 2.5cm long, stacked next to each other, with good success.  I have not
done any engineering analysis to determine how many beads or what kind of
ferrite material to use.  Maybe someone else can make a recommendation.  I
just used what was in my junk box and it worked fine.
-- replace the connector on the PC-end of the cable.  If you had to cut the
old connector off, you can use an ohmmeter to determine which wire went to
each pin.  Attach the braid to the shell of the connector (you may need to
replace a plastic-shelled connector with a metal-shell connector to do
this).

Note that a monitor may radiate through its case, if a plastic case was
used.  Others have described various techniques to line the case with
shielding material to reduce this kind of radiation.


-- Eric R3/K3NA

-----Original Message-----
From: owner-cq-contest at contesting.com
[mailto:owner-cq-contest at contesting.com]On Behalf Of Milt Jensen, N5IA
Sent: Monday, November 16, 1998 4:31 AM
To: cq-contest at contesting.com; topband at contesting.com
Subject: [CQ-Contest] PC Monitors



Fellow contesters and top band enthusiasts,

An amateur friend of mine recently started getting back into HF after a
number of years of absence.  In setting up his station he has encountered a
severe case of RFI associated with the monitor.  It is particularly bad on
160 Meters.

Either turning the monitor off or disconnecting the data line eliminate the
problem.

I have similar minor problems at my station, and have been able to live
with them.  However, we would both like to have some information on what
others have done to eliminate or greatly reduce this type of interference.

Are there any particular brands/models of monitors which experience has
shown to be less offensive?

What other steps have been implemented to accomplish this end?

PLEASE REPLY DIRECTLY TO    --   lgriggs at aepnet.com     --    Thanks, Milt,
N5IA

Gotta get back to packin' bags for XZ1N trip.  Talk to you from Burma
(Myanmar)!


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