Re: Computer RFI problems-FARMERIK <huelbe_garcia@...>

Hi Farmerik,

one of the most common sources of RFI (as noticed by colleagues here in
Brazil) are the Compact Fluorescent Lights (CFL). Some brands generate
lots of noise, other not that much. If you open one of these (be
careful) its base contains a high frequency, harmony rich oscillator.
Although the placeholders are marked in the circuit board, cheap brands
hardly install the inductors/capacitor meant to mitigate the RFI.

PY2WM DeMarco wrote an article specifically on CFL-generated noise and
how to solve it. The translated article (by Google Translator) is
available here:

the original article is here


----- Original message -----
From: "farmerik" <farmerik@...>
To: ultralightdx@...
Date: Wed, 12 Jan 2011 19:34:38 -0000
Subject: [ultralightdx] Re: Computer RFI problems-FARMERIK

It looks like the smaller mixture numbers are better for lower
frequencies, so I had that wrong in my first post.
My focus is the AC house wiring, all circuits seem to be loaded with
RFI. If I put a portable radio next to a filament bulb, I get tons of
RFI when I switch it on, and the higher the bulb wattage, the more
I started down this road when I had way too much noise in my Hammerlund
HQ-100, even on the standby position, with no antenna connected.
Not much sense working on antennas, if the house is so full of RFI.

I did read that excellent article [tried to understand what I could] and
went to the Fair-rite catalog. I don't see split chokes for LW and AM
though. I see Delta make power filters for RFI, which may be what I need
most. Thanks for the help, there is a lot to learn about this.

--- In ultralightdx@..., "Mike Mayer" <mwmayer@...> wrote:


I agree that the presentation you linked to is one of the best out there.

If you remember one thing it is that the suppression is proportional to the
square of the number of turns. The typical clamp-on ferrite is one turn (the
wire goes through once). If you look at some of the suggestions you will see
multiple turns. Two turns is four times as good, three turns is 9 time as
good, etc.

And yes, everything has either a noisy processor or a noisy switching power
supply. That is why another option is to use an external antenna away from
all of the noise sources in the house.

Mike Mayer


From: ultralightdx@... [mailto:ultralightdx@...] On
Behalf Of Peter Laws
Sent: Wednesday, January 12, 2011 10:22 AM
To: ultralightdx@...
Subject: Re: [ultralightdx] Computer RFI problems-FARMERIK

On Wed, Jan 12, 2011 at 08:35, farmerik <farmerik@...
<> > wrote:

Anyone out there RFI proofed there house already, and have any pointers?

This is hardly a FAQ, but it is a good tutorial on RFI. It's
ham-oriented, but RF is RF and a lot of it is receive oriented (as
opposed to RFI from your own transmitter, though that is covered,
too). I'm about a 1/3 of the way through it. :-)

Peter Laws | N5UWY | plaws plaws net | Travel by Train!


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