Video over Cat5 Extenders

Garbz · 19th March 2005, 12:41 AM

I've been looking around the net for a while on how to make a video extender. Something that can take a VGA signal from a computer and possibly run it over 400ft of cable without the ghosting which happens after about 6ft.

There's plenty of products available like this one http://www.altinex.com/Products/Dist...0CT_center.htm whic do this sort of thing but they seem a bit on the expensive side.

I've also tried using cat5 to transport the vga signal without any active components and while i did get the signal to an astonishing 12ft it's still no where near long enough to get to the projector on the roof.

What exactly do these boxes do? Is it possible to easily build one? I assume if they just amplify a video signal that simple opamps with sufficient bandwidth would suffice however, I doubt this is all that simple.

Any ideas?

GregMM · 19th March 2005, 01:23 PM

I havent tested or even attempted to test this, just thought of it now, but what about using 4 CAT5 cables, or one multiconductor cable, exten the sync wires directly, then use 3 8-bit ADC's one for red, green, and blue, use a cat5 for each, then three 8-bit DAC's on the projector end, seems like it should work

Garbz · 19th March 2005, 03:25 PM

well technically it would be 5 since there is Y rY and bY, Hsync and Vsync in the vga standard.

However in practice i doubt that they convert the signal from analogue to digital, and then back again. The main reason for this, wouldn't the high bandwidth of the video simply cause problems for this in the first place? I can imagine there would be significant loss in the ADC - DAC process.

cbm5 · 19th March 2005, 07:45 PM

You can get good quality VGA signals through an actual high-quality VGA cable designed for long runs. These cables have a separate coaxial cable inside for each R, G, B, and sync. I've regularly used runs up to 50 feet without significant degradation.

Otherwise, you will need a device like the Cybex Longview to get the signal any further.

Garbz · 20th March 2005, 02:09 AM

actually I just found another site wich recomends STP and shielded terminals as a requirement for this application.

I'll try that next.

justme · 20th March 2005, 08:23 AM

Quote:

Originally posted by Garbz

I've also tried using cat5 to transport the vga signal without any active components and while i did get the signal to an astonishing 12ft it's still no where near long enough to get to the projector on the roof.

Any ideas?

Did I miss the part where you explain why your projector is on the roof?

pinkmouse · 20th March 2005, 09:22 AM

Quote:

Originally posted by Garbz
Something that can take a VGA signal from a computer and possibly run it over 400ft of cable without the ghosting which happens after about 6ft.

That is solved easily by terminating the lines properly.

Why 400ft? Wouldn't it be easier just to have a cheap pc by the projector, and run that pc via your ethernet using a remote desktop utility?

Garbz · 20th March 2005, 11:14 AM

The projector is on the roof why? So people don't trip over it, so it doesn't obstruct things etc. It's the design of the room. It looks good this way, if it could be functional via vga too it would be even nicer.

I don't need 400ft, but the computer is a significant distance away. I mentioned 400ft, because that's how far the devices i've seen do this have stated.

I always thought that these contained active parts to amplify the signal or something, however the one i've looked at recently says you can achieve sending a 1280x1024 signal over 100ft only using STP. I did try running an SXGA signal over UTP but it just left us with a ghosting image.

If my 15pin -> STP converter doesn't work I'll be back to square one.

pinkmouse · 20th March 2005, 11:21 AM

Quote:

Originally posted by Garbz
The projector is on the roof why? So people don't trip over it, so it doesn't obstruct things etc

Ah, you mean the ceiling...

Quote:

I did try running an SXGA signal over UTP but it just left us with a ghosting image.

Terminate the lines properly!

Garbz · 21st March 2005, 02:18 AM

Yes ceiling that's what I meant.

The UTP ends are terminated properly, each colour is combined with a gnd for that twisted pair, and hsync is combined with vsync.

Apparently though STP is the only way this will work over long distances. I'll try this asap.

19th March 2005, 12:41 AM	#1
Garbz diyAudio Member Join Date: Dec 2003 Location: Brisbane	Video over Cat5 Extenders I've been looking around the net for a while on how to make a video extender. Something that can take a VGA signal from a computer and possibly run it over 400ft of cable without the ghosting which happens after about 6ft. There's plenty of products available like this one http://www.altinex.com/Products/Dist...0CT_center.htm whic do this sort of thing but they seem a bit on the expensive side. I've also tried using cat5 to transport the vga signal without any active components and while i did get the signal to an astonishing 12ft it's still no where near long enough to get to the projector on the roof. What exactly do these boxes do? Is it possible to easily build one? I assume if they just amplify a video signal that simple opamps with sufficient bandwidth would suffice however, I doubt this is all that simple. Any ideas?

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19th March 2005, 01:23 PM	#2
GregMM diyAudio Member Join Date: Nov 2004 Location: ny	I havent tested or even attempted to test this, just thought of it now, but what about using 4 CAT5 cables, or one multiconductor cable, exten the sync wires directly, then use 3 8-bit ADC's one for red, green, and blue, use a cat5 for each, then three 8-bit DAC's on the projector end, seems like it should work

19th March 2005, 03:25 PM	#3
Garbz diyAudio Member Join Date: Dec 2003 Location: Brisbane	well technically it would be 5 since there is Y rY and bY, Hsync and Vsync in the vga standard. However in practice i doubt that they convert the signal from analogue to digital, and then back again. The main reason for this, wouldn't the high bandwidth of the video simply cause problems for this in the first place? I can imagine there would be significant loss in the ADC - DAC process.

19th March 2005, 07:45 PM	#4
cbm5 diyAudio Member Join Date: Mar 2005 Location: Arkansas	You can get good quality VGA signals through an actual high-quality VGA cable designed for long runs. These cables have a separate coaxial cable inside for each R, G, B, and sync. I've regularly used runs up to 50 feet without significant degradation. Otherwise, you will need a device like the Cybex Longview to get the signal any further.

20th March 2005, 02:09 AM	#5
Garbz diyAudio Member Join Date: Dec 2003 Location: Brisbane	actually I just found another site wich recomends STP and shielded terminals as a requirement for this application. I'll try that next.

20th March 2005, 11:14 AM	#8
Garbz diyAudio Member Join Date: Dec 2003 Location: Brisbane	The projector is on the roof why? So people don't trip over it, so it doesn't obstruct things etc. It's the design of the room. It looks good this way, if it could be functional via vga too it would be even nicer. I don't need 400ft, but the computer is a significant distance away. I mentioned 400ft, because that's how far the devices i've seen do this have stated. I always thought that these contained active parts to amplify the signal or something, however the one i've looked at recently says you can achieve sending a 1280x1024 signal over 100ft only using STP. I did try running an SXGA signal over UTP but it just left us with a ghosting image. If my 15pin -> STP converter doesn't work I'll be back to square one.

21st March 2005, 02:18 AM	#10
Garbz diyAudio Member Join Date: Dec 2003 Location: Brisbane	Yes ceiling that's what I meant. The UTP ends are terminated properly, each colour is combined with a gnd for that twisted pair, and hsync is combined with vsync. Apparently though STP is the only way this will work over long distances. I'll try this asap.

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