Sorry I identified "Corcom" incorrectly.
I checked a sample and the actual filters that I used were Delta
Electronics 05DRCG5.
http://disti-assets.s3.amazonaws.com/quistelectronics/files/datasheets/4322.
pdf
Tom
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Tom W8JI
Sent: Tuesday, July 23, 2013 3:42 PM
To: topband@contesting.com
Subject: Re: Topband: Desktop Power Supply Brand/Noise Question
> I simply purchased 10 Corcom filters on ebay ( I think they were $2
> each + shipping). I cut a power supply cord (universal plug type)
> about 6 inches from the computer and wired the filter into a plastic
> electrical box with the other end of the cord out the other end of the
> box. I used standard electrical cable clamps to secure the cable to
> the box and added the cheapest electrical plastic cover. The whole
> thing cost me about $6 each and I built 5 of them in a couple of
> hours. The boxes live behind the computer so the blue color
> appearance doesn't matter. When I purchased newer computers, I just
> moved the filtered cord to the new computers.
That's OK, but be aware the corcom appears to be a typical design with
limited value for choking isolation.
See this page:
http://www.cor.com/pdf/DA.pdf
The windings appear to be linked magnetically, and the ground appears to
have no isolation. This seriously limits the effectiveness of the filter,
making it similar to beads over cords. The worse part is not having
isolation on the ground path.
The best part is the filter adds bypass capacitors, which when properly
sized either assist any added iron core cord chokes, establish a low or
controlled differential and common mode impedance, and often do a better job
than any practical choke system or core does.
I use a filter like this:
http://www.w8ji.com/images/filters/filter7.gif
It isolates and bypasses all three wires.
One of my tricks in a suburban environment was a three wire plug with two
.01 uF 250VAC UL/CSA bypass caps. No cord or anything on it. I moved that
plug around my house until I found a sweet spot that eliminated conducted
noise from the house next door. They had some battery charger that just tore
up 80 and 160 through our common sharing of a pole transformer.
73 Tom
_________________
Topband Reflector
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.3349 / Virus Database: 3204/6513 - Release Date: 07/23/13
_________________
Topband Reflector
|
