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I just set up a fairly expensive Belkin 8 port kvm switch at work. When i fired it up, I noticed that the video had degraded somewhat. The monitor looked much brighter and washed out, slightly fuzzy and the text was not as clear.

Almost like when you go from 100hz to 60hz refresh rate you notice a difference, this defintely looks worse. I'm using a 21" dell trinitron at work with modest resolution 1024x768x32 @85hz due to my not so great eyes. What could be causing this?

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Last Post by bobthenob
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Cheap monitor cabling (or overly-long cabling) is the primary cause of the signal degradation. If you're using thin, flimsy video cables such as those sold by CompUSA, Radio Shack, and the like you'll almost certainly experience the problems you describe.

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no im using the highest quality belkin cables they sell, along with a $400 kvm switch. why does the signal degrade like this? someone suggested it was an OSD overscan protection feature of the monitor where it cycles down to a lower refresh rate. i dont konw

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The monitor could be reacting to something it doesn't like about the signal, but it does seem like you're using high-quality components, so I'm really not sure why that would be the case. Is it a question of cable length perhaps?

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well no the cables are only a certain lengith, a few feet, to prevent that. ive read that all kvms will degrade video signal to some extent, just not sure why that happens.

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You'll get some signal degradation from any KVM's circuitry/wiring, but it shouldn't be anywhere near what you seem to be describing with a $400 Belkin box.

The cables don't seem to be the culprit; I suppose it's possible that the switch itself may be defective. Can you return it for another?

Also- some swithches and extenders have adjustments to compensate for things like cable length. Does yours have any such "tweaks"? If so, you might try twiddling with those.

Other than that, I'm pretty much out of ideas... :(

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Hello,

There will be a signal loss in every jump of the path. Yes, bad cables add to the problem, but so does bad grounding and stray electromagnetic fields. You could have a powerline in the wall causing the problem. I will also bet that the higher the resolution, the greater the distortion.

Any jumper / switch / connector will add to the loss of a signal. IN the RF (radio) world, a simple double-female barrel connector to splice coax together can cause 50 percent signal loss. The loss is because of the signal changing materials to travel over. Electricity travels in the form of electrons around the OUTSIDE of the wire (but inside the insulation).

Also, you mention a work environment. Lots of servers. Fans. Wires. There is a lot of Radio Frequency emitions in there, causing interference. Don't believe me? Take a cheap AM Transister pocket radio, and tune it to a non-station (a place where you hear some static, and not a station). Move it around your area, and hear where the buzzes are coming from. That is an energy wave causing a problem.

60 Hz refresh rates are very close to AC power cycles, thus will cause interference. First thing I do is change the rate to something greater, such as 72 - 75.

If clarity is very important, you may wish to consider directly using one computer as a master view station, and then use remote control programs such as VNC or Terminal Services to work your servers.

Christian

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I just got a MiniView KVM and was having similar issues with the video quality - slightly fuzzy and some thin characters on screen would appear to be partially blurred. I'm using the "standard" cables that came with the switch, so it could certainly be my cabling.

But... after reading kc0arf's post, I decided to play with the Hz rates on each attached machine. I first tried ramping up the Hz up to 75 and 85 but that didn't seem to change much. Then I tried setting it to 60Hz and viola! The image is as sharp as if it were directly connected.

Now I know this actually contradicts kc0arf's post, but I'm just relating my first-hand experience. Knowing dangerously little about interference patterns and cycles and stuff I suppose it could be that my KVM is tuned for 60Hz or something -- or I just got lucky. :)

Also, just to clarify, I adjusted the refresh rate in each machines OS "monitor" or "screen" settings preferences -- not on the actual monitor itself.

Hope this helps.
-Bob.

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