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 Post subject: RF interference and computers: Experiences anybody?
PostPosted: Tue Jan 28, 2003 5:16 pm 
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Location: Powell River, BC, Canada
RF interference... Sheilding... Unshielded cases...

It's a topic that comes up often. There are all kinds of do's and dont's. Is it all theory? How bad is the problem, is it a big deal? Which way does it work: does the computer bother other things, or do other things bother the computer? Questions questions questions. So I pose the question:

Question to the forum: what experiences have you actually had with RF interference and computers.

How did you notice the interference? What was happening? Was it a problem? How did you eliminate or avoid it? What was the hardware involved? Was it modified, and how? Do you run an unsheilded computer and yet have no interference problems?

I would gladly offer my experiences: essentially none. I have never seen any computer electrical interference. I do not discount this problem, but am extremely curious to find out what it actually amounts to in the real world.

Thanks, in advance. I hope this is an informative exercise.


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PostPosted: Tue Jan 28, 2003 5:36 pm 
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Only one, not with my computer but someone else's. She was on a cell or wireless phone wnne we were talking. Seemed a little buzzy, but no big deal. Then she tried to do something on her computer, can't recall what, and the connection got quite garbled till she stopped and stepped away from the desk. That's my one experience.


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 Post subject:
PostPosted: Tue Jan 28, 2003 6:10 pm 
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Location: Lithuania
Mobile phones ringing make my speakers crackle like crazy.

For a while I had my case off, whenever the PC was on, the TV a few feet away was un-watchable. I noticed it through the signal being 50% noise and the sound being muffled crackles =P

It was a P2-300 with 128mb RAM, a Voodoo Banshee and a bunch of other stuff that I'd imagine put out far less EMI than a modern PC. The only other electric thing in the room was the light, so I can't really say what effect it'd have on other complex electronics, but it probably wouldn't be good.


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 Post subject:
PostPosted: Tue Jan 28, 2003 9:49 pm 
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I've been running my system unsheided for 8 or 9 months now, with no ill effects. I often sit at my desk and talk on the cell phone.

On a related tangent: Isn't part of the reasoning behind EMF sheilding that it is supposed to project the computer from incoming waves? Has anybody had a computer related failure attributable to EMF?

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 Post subject:
PostPosted: Tue Jan 28, 2003 11:04 pm 
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Joined: Wed Jan 08, 2003 5:38 am
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Location: Tønsberg, Norway
I had a Sharp MZ-700 when I was a kid (Z80A processor @ 3.5 MHz). When it was turned on, the TV image got some rolling stripes (not the small one which got the signals from the computer, but the living room TV that got its signals from an antenna (which was in the attic over the computer)).

Never experienced interference with modern computers.


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 Post subject:
PostPosted: Tue Jan 28, 2003 11:09 pm 
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Alicey wrote:
It was a P2-300 with 128mb RAM, a Voodoo Banshee and a bunch of other stuff that I'd imagine put out far less EMI than a modern PC.

I don't know if that's a correct assumption. New systems are running most components at much lower voltages, at much higher frequencies, and using much less power doing it (per operation, the power goes up because the number of ops. has gone way up). That could actually cause a big reduction in switching noise (transistors turning on-off-on-off), as well as putting more of that noise into higher frequency ranges where we generally notice it less (TV's and radios are fairly low freq stuff), except maybe with things like cell phones (800mhz and up). Also I wonder about older vs. newer PSU's and HDD's, both of which have been improved lots in the last few years.


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 Post subject:
PostPosted: Wed Jan 29, 2003 4:49 am 
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Both of my rigs are run to spec: everything in place and closed up. When I'm on my portable phone and am near the running computers I start to get a clicking sound. If the computers are powered down I don't get the clicking noise. Obviously something's leaking out of my computer.

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 Post subject:
PostPosted: Wed Jan 29, 2003 6:24 am 
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Joined: Mon Sep 09, 2002 11:59 pm
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Location: Melbourne, Oz
I asked C3, the acrylic case people, about RF interference with acrylic cases. Here's their reply:

"We have not experienced any problems related to EMI/RF. Most all PC internal components made today are shielded from EMI/RF interference even without the protection of metal computer housing. We do recommend using round shielded IDE/Floppy cables as most IDE ribbon type cables do not offer any type of shielding. Many of today's computer cases incorporate some amount of plastic either in their front panel covers, floppy drives, CD-ROM drives, cooling fans and so on. If you have ever taken apart a laptop computer you know that it’s entire enclosure is made of plastic. Just because the plastic in our cases is clear does not mean that it offers less protection than the solid color plastics used in conventional cases and laptops.
"The real world test would be to remove the side panel of the computer you are currently using and if you do not experience any problems, you most certainly will not have a problem with our case."

Similar reply from ClearPC...

Although neither of them are likely to say 'yep, our PCs are a RF nightmare', their replies are broadly in line with other posts I've seen.


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 Post subject:
PostPosted: Wed Jan 29, 2003 10:15 am 
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Location: United States, Mobile, AL
were all gonna die a raidoactive death by the age of 35 anyways. I get more radiation for sitting infront of the monitor than all the time ive spent in the sun combined :D


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 Post subject:
PostPosted: Wed Jan 29, 2003 1:01 pm 
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leem wrote:
I asked C3, the acrylic case people, about RF interference with acrylic cases.

Thanks leem. C3 seems like a really cool company, and they gave a fairly interesting response. Nice that they didn't try to dodge the question. I have seen various forms of sheilding inside laptops though, including metal/conductive paint. The plastic alone offers absolutely no sheilding, not theirs or anyone else's. I don't think it's always a complete non issue. Their test of "remove the side panel..." seems like an honest, practical answer. It's what I would do. And the recommendation to use sheilded cables seems like a good one to, for airflow and cosmetics as well as RF. Otherwise I bet those cables would be amongst the worst antennea in the whole system.


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 Post subject:
PostPosted: Wed Jan 29, 2003 4:34 pm 
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Location: U.K.
I have noticed that if a GSM mobile telephone is in use near a mouse then it can trigger mouse movement or clicks. This has happened with a few different telephones, mice and computers.

I used to get interference on the radio if I was running the monitor at certain resolutions/frequencies.

I've known cheap PC speakers that pick up noise from all sorts of things. Door-buzzers and GSM telephones are the worst culprits.


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 Post subject:
PostPosted: Thu Jan 30, 2003 7:07 am 
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Location: London, UK
I get some interference from my pc through my guitar amp! Mainly it's from the monitor but a little gets through the case too. It used to be far worse when i ran with an open case, but now everything's locked up inside a PC60 it's much better :)


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 Post subject:
PostPosted: Thu Jan 30, 2003 9:36 am 
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Location: San Diego County
"were all gonna die a raidoactive death by the age of 35 anyways..."

48 and going strong, GamingGod, so you may have more time left than you think. On the other hand, I didn't start regularly sitting in front of a computer until 34 or so, either. May be time to update the old will.

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 Post subject:
PostPosted: Thu Jan 30, 2003 5:44 pm 
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Location: San Jose, CA
I've run various systems with no case/cover and haven't noticed any EMI/EMF grief - even when using the system near audio equipment or as a HTPC with all sorts of audio/video cables in close proximity to the system.

As people mentioned, cell phones are a different story. If my phone is near my IBM Trackpoint keyboard and the phone rings, the mouse starts moving across the screen by itself. Scary.

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 Post subject: Electrical interference with TV
PostPosted: Fri Jan 31, 2003 3:26 am 
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Joined: Thu Jan 30, 2003 2:59 pm
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Location: Isle of Man, UK
if i took off the side from my pc (a fair few cheap fans inside) the TV picture wasn't so good - stripes etc. Since putting in new fans (coolmaster and zalman) the stripes have gone


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 Post subject:
PostPosted: Fri Jan 31, 2003 10:50 am 
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Joined: Thu Jan 16, 2003 4:39 pm
Posts: 23
Location: UK
I got a lot of interference on my audio amp when I removed the psu
from the case,it was so bad I had to put it back in.But I think maybe
my ancient amp isn't well shielded! :) But having the side off the case
is no problem.


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