[RFI] Re: Computer noise and other RFI problems

Wendell Wyly Wendell Wyly" <w5fl@flash.net
Mon, 23 Mar 1998 09:51:21 -0600

No, DX4WIN is not the place to post RFI stuff.  I did not see your question
on the rfi reflector.

Radio Shack sells a pretty good RFI filter for phones.  I bough my neighbor
one and installed one on my phone and then bought the Radio Shack 43-585B
phone.  The filter cost $20 or you can buy the 43-585B phone that is RFI
"proof" for $20.  Both work well and both are recommended by the ARRL list
of RFI devices that they have tested.

Most problems with my computers have been through the keyboard and mouse or
monitor signal or power cord.  The 2 inch long ferrite clamp on "beads" sold
by radio shack are about $3 or $4 each.  I used about 25 of them on the
Stereo and 10 more on the leads from the computer to mouse and keyboard and
monitor.  Also put in better grounding for the transmitter.  Worked for me.
The problem in my case was that the equipment (computer) was not (never)
certified to FCC Class B as it is required by law to be.  I recently bought
a 17 inch monitor and made sure it met European Standards for radiation
(CE).  It is Mitsubishi Diamond Pro 87TXM and is MUCH quiter than my old
monitor.  No RFI problems with it with KW and 2 element quad 30 feet from
shack.  My computer case and the Metal ISOTEL surege suppressor are also
well grounded as is the printer.

I have no RFI of any kind with my TV and Component Stereo on any band with 1
KW.  The ferrite clamp on "beads" work well, unfortunately you need a bunch
of them.

Also used 2 of them on the wiring to the photoelectric eyes and manual push
button (at the control box) to the garage door opener.  Before that my wife
said she could hear me sending code through the garage door opener.  It
works perfectly now.

Wendell Wyly     W5FL     w5fl@flash.net
(A real 5 located near Weatherford Texas)
-----Original Message-----
From: Pete Smith <n4zr@contesting.com>
To: dx4win@qth.net <dx4win@qth.net>
Date: Monday, March 23, 1998 5:25 AM
Subject: RE: Computer noise

>At 06:50 PM 3/21/98 -0800, you wrote:
>>Friend of mine was having similar QRN from his computer. No amount of
>>toroids on the cords helped, nor did grounding.
>>What finally cured it was to install a filter-type plug in the computer
>>power supply. These are widely available at your electronic supply,
>>Allied, etc. Pain in the neck but it worked for him.
>Not quite the same question, but an allied one -- I've posted it to he RFI
>reflector at contesting.com but got no response (no messages at all) in a
>After two years with no RFI problems, my wife got a new computer and I'm
>bothering it.  Nothing terribly dramatic, but enough monitor flicker to be
>very annoying.  Just starting the pursuit of solutions, but my suspicion is
>that it's coming into her computer on the power or phone lines, because my
>antennas are 200 feet from the house so direct pickup through the computer
>or monitor case seems less likely.  I think I know how to handle the phone
>line, if that's the issue, but what do people recommend as a line filter?
>My last one was 30 years ago!
>73, Pete Smith N4ZR
>"That's WEST Virginia.  Thanks and 73"

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