[24hoursupport] Re: Cable generated interference
- From: yyixi001@xxxxxxxxxxxxxx
- To: 24hoursupport@xxxxxxxxxxxxx
- Date: Tue, 19 Aug 2003 17:35:00 -0500
Hi Robert,
I put a post to a Ham Radio Forum, and had ten views but no answers by
today. So I called and talked to the HRO guy in Anaheim, California, and
he said it's RFI, radio frequency interferance, running down your
cables. He said computers are very 'dirty' for stray RFI emissions. You
can also get problems with interferance from flourescent lights, and
from radios (he didn't say if music or HAM radios) interfering with
computers, and vice-versa. The deal is, you need to put something called
a 'ferrite snap bead' on each end of each of your monitor video and
power cables, which 'chokes' off the RF.
Here is a web page giving sort of an explanation of that (but don't buy
there; I'll get to that);
http://www.cardwellcondenser.com/PAGES/nr10.html
Here is where to get the 'ferrite snap beads' (a.k.a. 'ferrite
clamshells', or just 'ferrites');
http://www.allelectronics.com/cgi-bin/category.cgi?category=235&type=store
They're not really expensive, but the HRO guy says he has a room full of
HAM radio gear and computer gear, and I'm guessing he probably has the
accessory gear to detect his own stray rads, and likes everything
near-perfect, so he's telling me he puts them on both ends of every
cable he's got, mice, keyboard, networks, printers, scanners, and all
external peripheral devices. BUT--he told me you don't need to do it
that much. He said to just start by getting just a few of these and
snapping them only onto the monitor cables, so you end up with one on
each end of your monitor video and power cables, and see what results
you get before getting more of them to put on anything else. He said
it's 'as much art as science', and you have to experiment with them a
little.
I'd guess that just doing the monitor cables may be enough, whereas
someone like him, he can set up his test gear and turn up the
sensitivity and see a very slight RFI reading on just about any piece of
computer gear he aims it at, and so he goes after it like that, with a
ferrite on both ends of every single thing he's got. But he admits it's
not necessary to do all that. So that's where he says to just do the
monitor cables first, and go from there. Or if you want to buy a whole
bunch of them, which is what he does, then just try to match up the hole
sizes of the ferrites to the cable thicknesses.
The way you put them on, is to get the clamshell ferrite that has the
best match for the diameter of cable it's going around, for which an
inexpensive plastic caliper measuring device would help, but if you
don't have that just eyeball it with a ruler. You snap it on near to the
plug at the monitor end, then slide it over to butt it up against the
plug, or against where the plug comes out of the monitor, and leave it
there permanently. Then do the same at the other end. It should not
cause any other problems, and is supposed to help or cure the RFI
problem, which is apparently what is causing monitor interferance.
He also said most monitors already come with a built-in 'ferrite' on the
video cable; it's the little cylindrical knob on the video cord that
makes the video cable look like a skinny little boa constrictor that
swallowed a D or C cell battery. That's the ferrite. I'd guess that,
like a rubber magnet, it's platic with iron particles or one or more
iron cylinders embedded in it ('ferrite' = 'iron'; I think). So I'd say
the idea is, if you're getting RFI, then you need to add a few more,
onto the other end of the monitor cable, and then the monitor power
cables. If that doesn't do the job, the HRO guy says to go for some of
the other computer externals with cables, and start playing around with
the ferrites. But the way it's done; you always snap them on, then slide
them down to either or both ends as close as possible to where it comes
out of the computer, or to the external device, and leave it on.
Some of the bigger computer supply stores also sell these ferrites,
although the sales person at PC Mall said he never heard of them.
Please let me know if I can help any further.
cheers,
Roland
General Class HAM Lic. KC6RRL
"Robert Carneal carnealr-at-adelphia.net |24hoursupport/1.0-Allow|"
wrote:
>
>
> I would very much appreciate that.
> Thank you.
>
> Robert
>
> At 10:33 AM 8/18/2003 -0500, you wrote:
>
> >
> >I've been thinking I might could check with an amateur radio egroup and
> >ask them, and this seems like a good time to do that. I'll see what I
> >can come up with.
> >
> >cheers,
> >
> >Roland
> >
> >
> >
> >
> >"Robert Carneal carnealr-at-adelphia.net |24hoursupport/1.0-Allow|"
> >wrote:
> > >
> > >
> > > <Copy>
> > > The top of the page includes a sublink for 'store location', listing
> > > stores
> > > across the US. I chose Denver, Colorado, as being sort of 'middle' US, and
> > > the following link;
> > > <End>
> > > Thank you. I will write them tomorrow. Voice communications via telephone
> > > isn't possible for me; I am hearing challenged and depend on lip reading.
> > >
> > > Robert
> > >
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