On Wed, 2012-07-04 at 09:14 -0700, Jim Brown wrote:
> On 7/4/2012 6:10 AM, Bill Cromwell wrote:
> > Next I'll be getting my hands on some ferrite core materials and looking to
> > see just how far I can reduce the noise.
>
> When faced with a noisy computer, the first thing I'd try (other than
> replacing the noisy supply) would be a multi-turn choke on the power
> cable, optimized (number of turns and core) for the band(s) where you're
> hearing the most noise. If noise remained, I'd next tackle the video
> cable and the printer cable. Use the graphs in Appendix One of
> http://audiosystemsgroup.com/RFI-Ham.pdf as a guide to picking the cores
> and winding the chokes.
>
> Do your fellow hams another favor -- post the brand names and/or vendors
> of both the noisy power supply and the one that fixed your problem (if
> it does). :)
>
> 73, Jim K9YC
Hi Jim,
This PC did not produce any interference before I replaced the power
supply. That tells me I shouldn't expect any interference from any of
the parts that were in use before. I'll post the information about the
power supplies. In fact the evil one has a Circled A logo and is named
named "Vista" and is a 500 watt, dual fan, ATX power supply. I have two.
The one that's online has been modified with a partial EMI filter. One
has not been modified at all. Both were equally bad before the mods.
I'll look at Mouser to see what kind of modular filter might be
available to solder in where I have removed the jumpers. A quick scan
showed that those are not terribly expensive. Now I have made physical
measurements of the filter space and circuit board pads I can take a
closer look to see what will fit. The internal EMI filter is right at
the power cord connector. The partial filter I installed has already had
a remarkable effect.
Another tower I have here was using one of the new supplies to wipe out
my radio operations. I put an old, lower capacity supply into that one
and it quieted right back down. This one needs more steam so I can't put
my old 300 watt supply in and expect it to survive for very long. In
fact, guess how I killed the original power supply (hanging my head in
shame).
I expect things to just keep getting better :)
73,
Bill KU8H
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