Topband: Computer RFI on 160

[Bill Tippett]

In 2004 I had a problem with a neighbor's PC birdie drifting onto the
Chesterfield Island (TX9) expedition frequency.  Fortunately it was a
new "white box" computer assembled by a local company and I was able
to return it and have the power supply exchanged for free.  Problem
solved...I thought.

Recently I began hearing another birdie on 1822.  Using my Beverages
and my trusty Sony ICF-2010 receiver, I was able to trace the birdie
to the same neighbor.  The Sony unit is especially nice since you can
tune it to the exact frequency of any birdies, and the internal whip
antenna is quite directional using the internal S-meter once you get
close to the source.  Fortunately I don't have many neighbors so it
was fairly easy to locate.

They still had the same computer but apparently it had developed the
same problem over the years.  On-site I tried about 8 turns of the
power cord through a Mix 31 2.4" toroid, but that didn't dent the
noise enough.  Fortunately these neighbors are good friends so they
suggested I take their computer and fix it.  When I got home and
opened the power supply, I saw there was zero filtering on the modular
plug. Fortunately I had purchased several CORCOM 6EF1 EFI line filters
several years ago for ~$5 each.  A few minutes with a screw driver and
soldering iron and I had the standard modular plug replaced with the
CORCOM.  Problem solved forever!  (I hope).

Although the 6EF1 lists for ~$15 each from normal distributors, I see
someone on eBay is selling them for $75/10 units.  I've seen them for
sale at lower quantities and prices so you might watch for some to
appear.  Having a few of these in your junk box for emergency RFI
fixes might be a good idea.

73,  Bill  W4ZV