KVM fuzzy video? It's the cables (stupid)!

  • Thread starter Thread starter Todd H.
  • Start date Start date
T

Todd H.

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/IWCatProd..._Id=&Section_Id=1546&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 shit"-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 said:
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!
Click to expand...

Also:
Shorter cables, cables with ferrite beads on them, lower refresh rate.
Don't forget the cable from the KVM to the monitor.
 
Chris Hodges said:
Also:
Shorter cables, cables with ferrite beads on them, lower refresh
rate. Don't forget the cable from the KVM to the monitor.
Click to expand...

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. said:
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 <
Click to expand...
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.
 
Todd said:
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.
Click to expand...

Fair enough - now why don't they make _short_ kvm cables - that would
help immensely!
 
Alien Zord said:
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.
Click to expand...

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. said:
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.
Click to expand...
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.
 
On 19 Nov 2003 15:28:13 -0600, (e-mail address removed) (Todd H.) wrote:

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.
Click to expand...

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.


Dave
 
kony said:
On 19 Nov 2003 15:28:13 -0600, (e-mail address removed) (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.
Click to expand...
And a correct termination of the RGB lines is equally important as "ringing"
is what causes fuzziness and reflections cause ghosting.
 
kony said:
On 19 Nov 2003 15:28:13 -0600, (e-mail address removed) (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.
Click to expand...

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,
 
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