K1TTT Technical Reference
'treating' sources of rfi can be done several ways.
1. for long cables roll them up into tight coils, for stubborn cases
wind them around ferrite chokes (radio shack has or at least had some
that were pretty good)
2. real stubborn cases of cables can be shielded with aluminum foil,
connect the aluminum foil to the computer case and if possible at the
accesory it goes to.
3. radiation through cases (this is if you still have noise after you
have disconnected all cables except power): if case is not metallic
you may be out of luck, otherwise scrape paint off inside of case at
screws to make sure there is good metal to metal contact.
4. radiation from monitors can be tough since they make a lot of noise
and are usually in plastic cases. i was able to cure one by wrapping
the whole thing except the screen in aluminum foil. but to keep it
cool i had to cut a hole in the foil and add a muffin fan. newer
low radiation monitors seem the best i have heard.
5. some surge protectors seem to increase computer noise, if you have
one take it out temporarily and see if that helps.
hope that helps a bit.
p.s. while it is not directly related to your question you might want
to check out http://www.fcc.gov/Bureaus/Compliance/WWW/tvibook.html
for general backround on radio interference. also the arrl site
at http://www.arrl.org/ may have some links to other info but i
haven't checked them out yet.
firstname.lastname@example.org or email@example.com
EMF Problem Solved
Fri, 13 Sep 1996 12:29:41 -0700
firstname.lastname@example.org (Art Wallace)
W E A R E S A V E D !
Received my Damark Catalog today and lo and behold, an item that will
solve all our EMI problems. It is called an Earth Energy Pendant and is
worn around the neck. Here is what the catalog says:
"The Earth Energy Pendant is designed to be a grounding device for the
increasingly prevalent electromagnetic fields (EMFs) surrounding TV's,
computers and other electrical devices. Increased health and
revitalized energy are just a couple of the many benefits reported by
some wearers of this tiny white metal energy rod. Made of magnetic
alloys, it also has a rare Takionic Energy Bead mounted on its sterling
silver cap. The Takionic crystal, developed in Japan, is tuned to the
Schumann Resonance (7.83hz). Choose from a silken cord or sterling
Wow! For only $89.00 you can prevent your neighbors from having two
headed kids and you can give them "Revitalized Energy". If Japan
developed the Takionic crystal, then maybe they could just put them in
every rig they ship along with some decent CW filters.
Get you Visa or Mastercard ready!!!
Art KK6XN :)
Tony Brock-Fisher <email@example.com>
Re: POWERLINE NOISE
I've had similar problems with a 13 KV line in front of my house.
I suggest using two methods to pinpoint the source:
1. 135MHz (VHF) AM detecting radio and small yagi - 3 or more
elements. This is very directional but doesn't correlate
well with noise at HF. There was a QST article some years back.
2. 20 Meter QRP rig with handheld shielded magnetic loop. Not very
sensitive, but the loop has a directional null which can be used
to locate sources, and the results correlate well with the Home
In my case, the very coorperative power company replaced EVERYTHING
on the pole infront of my house - including the POLE and the transformer.
No Joy - the noise was still there. At least it was until the first
freeze of the fall that year. I noticed a piece of a bell insulator
on the street as I was walking in the morning. Called the power company,
they replaced the broken insulator. No more noise! We were close - only
1 pole off!!
-Tony, K1KP, firstname.lastname@example.org
A really cheap thing to do for your shack computer is to buy it a shielded
power cord. At a recent hamfest, I found 4 shielded ones in a mixed pile of
cords, and got them for $1 each. Sometimes clone PCs don't have shielded
cords. I haven't done any measurements before/after, but it sure seems like
a good idea.
Also, somebody asked about shielded PCs: I have seen fully shielded PCs
manufactured by IBM. They will have a small T on the logo plaque (for
Tempest). Sometimes you can find a PC/AT case that is part of one of those
systems, and it will have metallic coating on the inside as well as metal
finger joints. The complete systems will have shielded keyboard, monitor,
power cord, and mouse. Lots of RFI suppression.
Thanks for all the effort that went into your super web site!