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#1
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KVM fuzzy video? It's the cables (stupid)!
I'd like to share the solution I found to fuzzy text problems I was having with a new KVM switch a 17" flat panel LCD monitor (native 1600x1200 resolution). Short story: "High integrity" KVM video cables features co-axial conductors for the VGA RGB signal are absolutely worth the extra money! The longer story: My first KVM was a Belkin OmniView SE 4-port KVM switch. It works beautifully for me into a 17" traditional CRT that I run at 1280x1024 resolution usually 6 or 10 foot Belkin standard KVM cables. No problems at all. Now, my next KVM switch a different computer--one that sports a 17" NEC LCD 1760NX flat panel LCD that runs at 1600x1200 resolution. I bought a Belkin "OmniView. SOHO Series 2-Port KVM Switch with Audio Part # F1DS102T" and I figured the same ole standard 6' KVM cable would do fine...but I was wrong. You need the better cables for this resolution. If you need to do 1600x1200 resolution, my experience is that: Belkin's base SOHO series KVM cables won't do. Your display will look fuzzy to you. If you scrutinize closely, you'll notice ghosting of text and banding, and general badness. Text won't be very readable at all. So I bought.... Belkin's Gold series KVM cables. Doh! only to to learn that they're the same as above, only with 24k gold plating on the connector. The cable itself is electrically identical to the above, and the result...identically crappy. Gold series is marketing cruft--don't bother. But... Belkin's Pro Line series of "high integrity" KVM cables makes it happen (e.g http://catalog.belkin.com/IWCatProductPage.process?Merchant_Id=&Section_Id=1 546&pcount=&Product_Id=92851 ). The silver bullet appers to be their use of co-axial conductors for teh RGB signals. The co-ax eliminates the bleed onto the other conductors that causes ghosting, banding, and general "monitor looking like ****"-tedness. Virtually indistinguishable from having the monitor directly plugged into the machine. Once I used one of these, all my problems with ghosting, banding, and poor display just went away. Here's hoping folks with similar problems stumble over this post before wasting as much time with various cables before finding the solution. Best Regards, -- Todd H. http://www.toddh.net/ |
#2
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Todd H. wrote:
I'd like to share the solution I found to fuzzy text problems I was having with a new KVM switch a 17" flat panel LCD monitor (native 1600x1200 resolution). Short story: "High integrity" KVM video cables features co-axial conductors for the VGA RGB signal are absolutely worth the extra money! Also: Shorter cables, cables with ferrite beads on them, lower refresh rate. Don't forget the cable from the KVM to the monitor. -- Chris ----- Spamtrap in force: to email replace 127.0.0.1 with blueyonder.co.uk |
#3
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Chris Hodges writes:
Todd H. wrote: I'd like to share the solution I found to fuzzy text problems I was having with a new KVM switch a 17" flat panel LCD monitor (native 1600x1200 resolution). Short story: "High integrity" KVM video cables features co-axial conductors for the VGA RGB signal are absolutely worth the extra money! Also: Shorter cables, cables with ferrite beads on them, lower refresh rate. Don't forget the cable from the KVM to the monitor. I agree in general, however, in my case, none of these helped. I'd replaced the stock monitor cable with a supposedly high quality 2 footer, and the others were 6 footers (shortest available), and the results were immeasurably more horried than the full monitor cable length with a good co-ax 6' KVM cable. -- Todd H. http://www.toddh.net/ |
#4
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"Todd H." wrote in message
... I'd like to share the solution I found to fuzzy text problems I was having with a new KVM switch a 17" flat panel LCD monitor (native 1600x1200 resolution). Now, my next KVM switch a different computer--one that sports a 17" NEC LCD 1760NX flat panel LCD that runs at 1600x1200 resolution. snipped I don't know of any 17" LCD monitor with native res. of 1600 x 1200. Especially not the NEC as I'm starring at one right now and its definitely 1280 x 1024 pixels. |
#5
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Todd H. wrote:
Also: Shorter cables, cables with ferrite beads on them, lower refresh rate. Don't forget the cable from the KVM to the monitor. I agree in general, however, in my case, none of these helped. I'd replaced the stock monitor cable with a supposedly high quality 2 footer, and the others were 6 footers (shortest available), and the results were immeasurably more horried than the full monitor cable length with a good co-ax 6' KVM cable. Fair enough - now why don't they make _short_ kvm cables - that would help immensely! -- Chris ----- Spamtrap in force: to email replace 127.0.0.1 with blueyonder.co.uk |
#6
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"Alien Zord" writes:
"Todd H." wrote in message ... I'd like to share the solution I found to fuzzy text problems I was having with a new KVM switch a 17" flat panel LCD monitor (native 1600x1200 resolution). Now, my next KVM switch a different computer--one that sports a 17" NEC LCD 1760NX flat panel LCD that runs at 1600x1200 resolution. snipped I don't know of any 17" LCD monitor with native res. of 1600 x 1200. Especially not the NEC as I'm starring at one right now and its definitely 1280 x 1024 pixels. Greetings alien, Indeed-my mistake, and thanks for pointing it out. Feel free to do a mental/search-replace of all instances of 1600x1200 with 1280x1024 in the original post regarding the flat panel NEC LCD 1760NX. Now this becomes rather interesting since it eliminates resolution as the root cause of my observations. I'll need to figure out whether it's the difference in KVM switch models that's causing this sensitivity, the different video cards, or sensitivities of the different monitors that are triggering this need for the high integrity cables for this particular setup. As you can see from the original post, I've used several identical cables on the two setups (Asus integrated vido-Omniview SE 4-port-IBM CRT with std cables versus Matrx G400-2port new Belkin KVM-NEC LCD)with markedly different results with respect to cable needs. Best Regards, -- Todd H. http://www.toddh.net/ |
#7
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"Todd H." wrote in message ...
Now this becomes rather interesting since it eliminates resolution as the root cause of my observations. I'll need to figure out whether it's the difference in KVM switch models that's causing this sensitivity, the different video cards, or sensitivities of the different monitors that are triggering this need for the high integrity cables for this particular setup. I use a 4 port Rextron NovaView KVM with my servers feeding 19" Iiyama Diamondtron running at 1152 x 864 because the monitor suffers from horizontal distortion at higher resolutions. 3 servers have G400 and one G100 graphics cards. The combo cables are triple coax type and 3m (10 feet) long because the distributor at the time didn't have any shorter ones yet the display is sharp and ghost free. |
#8
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#9
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"kony" wrote in message
... On 19 Nov 2003 15:28:13 -0600, (Todd H.) wrote: I wouldn't assume that your setup is unique in needing "hi-integrity" cables, it is generally known that retaining image quality with any extension cable requires good cables, is the way it's been for years, long before modern monitors with very high resolution and refresh rate capability or cards with fast DACs. And a correct termination of the RGB lines is equally important as "ringing" is what causes fuzziness and reflections cause ghosting. |
#10
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kony writes:
On 19 Nov 2003 15:28:13 -0600, (Todd H.) wrote: snip I'll need to figure out whether it's the difference in KVM switch models that's causing this sensitivity, the different video cards, or sensitivities of the different monitors that are triggering this need for the high integrity cables for this particular setup. As you can see from the original post, I've used several identical cables on the two setups (Asus integrated vido-Omniview SE 4-port-IBM CRT with std cables versus Matrx G400-2port new Belkin KVM-NEC LCD)with markedly different results with respect to cable needs. I wouldn't assume that your setup is unique in needing "hi-integrity" cables, it is generally known that retaining image quality with any extension cable requires good cables, is the way it's been for years, long before modern monitors with very high resolution and refresh rate capability or cards with fast DACs. Nah, I don't think it's unique either...but I remain curious as to why I'm getting away with the non-co-ax standard cables in this setup: Asus integrated video-+-Omniview SE 4-port F1d104 --IBM G76 17" CRT IBM T23 Thinkpad -----+ But standard cables are completely unacceptable in this setup: Matrox G400---+-Omniview SOHO F1DS102T - NEC LCD 1760NX Apple iBook---+ Nor a test using the sam machine as above: Asus integrated video-+-Omniview SOHO F1DS102T - NEC LCD 1760NX Apple iBook-----------+ With everything running running 1280x1024 @ 75 Hz (except the iBook). Best I can tell, either this NEC LCD 1760NX appears to be more sensitive to cabling than my IBM G76 CRT, or the 2port Belkin OmniView F1DS102T KVM switch is more sensitive to cabling than the 4-port Belkin OmniView SE F1D104. When I get around to dragging the LCD downstairs, I suppose we'll have an answer to that riddle. :-) I'm intrigued by Alien's mention of termination quality. Does anyone know how internall KVM switches work on video? Are the video signals buffered and regenerated, is there a mechanical switching (i.e. relays--doubtful at best, IMO), or and electronic switching? I am wondering if KVM switches vary in their ability to properly terminate video connections from connected computers. Best Regards, -- Todd H. http://www.toddh.net/ |
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