How long can video cables be without losing signal?

[Fraggable]

I have been put in charge of figuring out how to set up a digital signage network here at the school I work at, and need some help figuring out what I'm looking for.

We plan to have 5-7 32-37" LCD TVs set up around the school - some of them will be 50-100' from the video source, a couple of them will be 100-250', one of them will be 500-750' away in another building. They will all show the same thing - a PowerPoint presentation that loops all day showing daily announcements, short video clips, and pictures. They will not show regular TV.

I need to know what kind of video cables I can run those distances and what kind of amplifiers I might need. They will run at a resolution of 1280 X 768 or 1366X 768.

 

[Matthias99]

We plan to have 5-7 32-37" LCD TVs set up around the school - some of them will be 50-100' from the video source, a couple of them will be 100-250', one of them will be 500-750' away in another building. They will all show the same thing - a PowerPoint presentation that loops all day showing daily announcements, short video clips, and pictures. They will not show regular TV.

I need to know what kind of video cables I can run those distances and what kind of amplifiers I might need. They will run at a resolution of 1280 X 768 or 1366X 768.

No standard video protocols will go that far without massive signal loss. 50-100', maybe. Much longer than that... no. DVI is better than VGA/component, but none of them are made for really long-distance transmission.

Distributing signals over coax *does* work pretty well, though you would probably need some amplifiers for that sort of distance. Also, 'normal' RF encoder/decoders will only give you standard-def -- ~640x480i. Not gonna look real good. It's possible to push high-def signals through coax -- but that stuff's not cheap. I mean, very not cheap. You can also get wireless transmitters for composite/S-Video -- again, anything beyond 640x480 will be very pricey, and I don't know about the distances you're talking about...

If you want to push high-def signals that far -- honestly, it's probably better to put a cheap computer at each endpoint and run Ethernet (will go 100 meters easy, and you can daisy-chain through dirt-cheap switches to go farther), or a wireless network with amplified directional antennas. Then just put the presentation up on a network share. You could either use VNC to control the remote systems, or set up some sort of scripting so that they will go grab the latest presentation, say, once an hour and start looping it.

 

[bobsmith1492]

Yeah, put a cheapo box at each point and network them.

 

[Fraggable]

We have a great network already, if I could find a way to cheaply stream the video over the network maybe I would do that.

I was planning to set the video source to grab the file from some shared area on our server as matthias suggested. Putting systems at each display is not ideal, however it might be necessary.

Any more ideas?

 

[HexiumVII]

They have VGA to ethernet splitters that go up to HD resolutoins. They get pricey though.

 

[Peter]

Analog signals lose quality with every inch of cable, right from the start. Digital signals like DVI or HDMI transmit over a certain length of cable at 100% quality, and then immediately drop out to unusable as you go over the maximum length.

 

[intogamer]

Originally posted by: Peter
Analog signals lose quality with every inch of cable, right from the start. Digital signals like DVI or HDMI transmit over a certain length of cable at 100% quality, and then immediately drop out to unusable as you go over the maximum length.

So whats the maximum length?

 

[Peter]

As I said, there is no fixed maximum length.

For analog signals, it depends on two factors - (1) how good is YOUR cable electrically, and (2) how much quality degradation is still good enough for YOUR application.

For digital signals, (1) is the only factor ... an electrically better cable will leave the signal intact over a greater length than a poorly engineered one. There is a clear specification for how good the signal must be at the receiving end; in theory, cable assemblies are to be tested for compliance - feed them a marginal input signal, and see whether the output signal on the far end is still within specification.

As a retail customer, you can but rely on the fact that when it says DVI on the box then it should be compliant - and if you find it non-working with YOUR stuff, return it and get a better one.

 

[DieHardware]

The first Google hit...

http://www.opticis.com/productlist.htm

 

[Steve]

Originally posted by: intogamer

Originally posted by: Peter
Analog signals lose quality with every inch of cable, right from the start. Digital signals like DVI or HDMI transmit over a certain length of cable at 100% quality, and then immediately drop out to unusable as you go over the maximum length.

So whats the maximum length?

Just for the record, I can use my 12 foot component cables from Acoustic Research, or my standard issue 3 foot 'generic' component cables from Comcast, and my picture's just as good either way.