[24hoursupport] Re: Cable generated interference
- From: Robert Carneal <carnealr@xxxxxxxxxxxx>
- To: 24hoursupport@xxxxxxxxxxxxx
- Date: Wed, 20 Aug 2003 10:02:04 -0500
Hm, that makes sense. There is a board at the back of the desk which keeps
ladies dresses private and also holds the desk together. I drilled a hold
dead center of it and ran the video cables right through it.
Let me throw this at you: If I were to get some ferrite beads, and put them
on sides of the hole (middle of cable, so to speak) that -should- reduce
interference?
The cables already have a something on each end of the cable, so I am
guessing I just need to add some right around where they are bundled. Does
that make sense?
Also, after reading you email, I got a horror thought. I use a Microsoft
Wireless Intellimouse Explorer. That has to have some way to
"communicating" (I am assuming radio waves, I am not a communications
engineer.). At the computer where the receiver plugs in, there is no
ferrite bead at all. Should I make this a prime suspect?
Thank you.
Robert
At 05:35 PM 8/19/2003, you wrote:
>
>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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