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Are the ferrites at the end of monitor cables (both DVI and VGA) supposed to make them less lossy?

Posted on 2006-11-20
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Last Modified: 2010-04-29
Hi all,

Are the "ferrites" (the round things) at the extremes of a monitor cable (both DVI and VGA) supposed to make them less lossy? I.e., better for my own use.

The issue is I bought a KVM DVI Switch that came with cables. I pointed out to the shop that the cables look sub-standard, cos although they are quite thick, they don't have them round things at the ends. They said it doesn't matter. I was getting noise with on my big external screen, and when I borrowed somebody else's DVI cable (with them round things, but thinner) the noise was reduced by about 50%.

Also I read somewhere that the ferrites just stop the cables from interfering with outside things so much.

tia

avi
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Question by:progtw
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5 Comments
 
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Assisted Solution

by:JamesTX10
JamesTX10 earned 50 total points
ID: 17980547
Hi progtw,
RFI filters can be pretty important when cables are run through big bundles of other cables or near strong power supplies. They help reduce noise on the line.


JamesTX10
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by:wlennon
wlennon earned 50 total points
ID: 17980852
In addition to what Jame said, they also neutralize wireless components such as your Power Supply, Cordless Phones, Mirowaves, Routers...They are even on my Dish HD Reveiver.

Thanks,

Wes
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LVL 16

Assisted Solution

by:Brian Pringle
Brian Pringle earned 75 total points
ID: 17983458
Their purpose is to prevent the long cable run from acting like an antenna.  They are not a requirement and are not only used on good equipment.  Sometimes, vendors will use sub-standard cables and install them so that the end user does not notice there is a problem.  

Are they good and useful?  Sure.  Are they required?  Not necessarily.  It depends on the company, components, and if they installed quality EMI shielding *inside* the cable.
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Accepted Solution

by:
kode99 earned 225 total points
ID: 17984269
Usually a big cable means good shielding.  A KVM cable is several cables in one so even though your cable may look big it could just be due to the bundle,  probably 3 good shielded cables would be a lot bigger.  I prefer KVM's that don't come with cables (or built in cables) and then buy decent cables for them.

Here's a decent VGA KVM cable,  as you can see its a pretty big wire,
http://www.startech.com/Product/ItemDetail.aspx?productid=SVPS23N1_6&c=CA

The DVI version is about the same though they dont show the combined cable in the picture,
http://www.startech.com/Product/ItemDetail.aspx?productid=USBDVI4N1A6&c=CA

I can usually get the startech cords for about half price locally,  I think newegg also have them far lower than on the startech store.

Sometimes a thin less shielded wire is fine, really depends on what else you have close by and how long the wires are.  You might want to take a look at other things,  maybe cords all wrapped up with each other,  crappy speakers are often culprits too.  Maybe change things up a bit, if you have not allready.

I had once case where there was a HUGE AC service on the other side of a wall,  we had to move  the workstation across the room to clear it up no matter what cables we used.  The problem never showed up until we one day somebody changed the resolution on the monitor,  had been fine for 4 years or more.
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by:progtw
ID: 17985650
Wow, I didn't expect so many answers. Well, I will raise the points so that everybody gets something. I will give according to quantity of text...

avi
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