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/Distribution_Amplifiers/DA1930CT/DA1930CT_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?
There's plenty of products available like this one http://www.altinex.com/Products/Distribution_Amplifiers/DA1930CT/DA1930CT_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?
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
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.
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.
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.
Otherwise, you will need a device like the Cybex Longview to get the signal any further.
actually I just found another site wich recomends STP and shielded terminals as a requirement for this application.
I'll try that next.
I'll try that next.
Garbz said:
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?
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.
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.
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.
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.
Interesting that they say to use STP. VGA uses unbalanced signals and so STP is not really any better than coax. In fact, I'll bet you could get very good quality by using separate runs of 75 ohm TV coax (VGA uses 75 ohm termination) and make sure the connections are solid and shielded.
As far as converting to digital, you'd need a very fast high bandwidth convertion system. The three video lines need to work up into the megahertz.
As far as converting to digital, you'd need a very fast high bandwidth convertion system. The three video lines need to work up into the megahertz.
Using coax lines begins to add bulk. And I simply cringe at the thought of terminating 5 lines of 75ohm coax to a DB15 plug 😱
It's simpler and cheaper to just use a VGA cable that already has the separately shielded cables inside. Just searching eBay for "vga cable" brings up a lot of options. Like 50-foot triple shielded VGA extension cables, 2 for $35.
you can use cat-5 cable, but the impeadance mismatch is what is causing the ghosting (signal reflections).
Like it was stated in a previous post, buy the proper cable, ie: one that has coax for each colour. For a long run, it is well worth it if you want to maintain a quality image.
As far as the VGA drivers, for the most part, the amplify the signal to drive the long cable runs. Look up EXTRON, we use these at work for long runs.
Like it was stated in a previous post, buy the proper cable, ie: one that has coax for each colour. For a long run, it is well worth it if you want to maintain a quality image.
As far as the VGA drivers, for the most part, the amplify the signal to drive the long cable runs. Look up EXTRON, we use these at work for long runs.
Cable wiring diagram
Hey Guys,
I am glad I found this post. I was getting ready to spend money on a cat 5 extender ( and I only need to extend a computer monitor about 30 feet... )
I will probably go the 3 - 75 ohm coax wire route ( plus sync ).
Just wondering how the termination is actually wired...
I assume coming from a newer computer video card, I don't need termination on the source?
But how do I wire the destination? I can find the pinouts online, but is the 75 ohms before I "tap" the signals, or after, and is the resistor between the "hot" and ground?
I just don't get how to wire the terminations...
Thanks for your help guys.
Regards,
Luke
Hey Guys,
I am glad I found this post. I was getting ready to spend money on a cat 5 extender ( and I only need to extend a computer monitor about 30 feet... )
I will probably go the 3 - 75 ohm coax wire route ( plus sync ).
Just wondering how the termination is actually wired...
I assume coming from a newer computer video card, I don't need termination on the source?
But how do I wire the destination? I can find the pinouts online, but is the 75 ohms before I "tap" the signals, or after, and is the resistor between the "hot" and ground?
I just don't get how to wire the terminations...
Thanks for your help guys.
Regards,
Luke
400ft is a long distance for a video signal.
Unfortunately I see no cheap solution.
I have some work esperience as an audio-visual technician, and when we had to install video hardware on such distances:
-convert to optical
-convert to ethernet
-use a RGBHV signal on 5 lines, with a heavy cable (sorry I forgot the exact reference) around 4cm in diameter, it's made of 5 VCB75 or VCB100 coax cables.
As Ringram said, Extron is good stuff, Kramer also makes good products.
Unfortunately I see no cheap solution.
I have some work esperience as an audio-visual technician, and when we had to install video hardware on such distances:
-convert to optical
-convert to ethernet
-use a RGBHV signal on 5 lines, with a heavy cable (sorry I forgot the exact reference) around 4cm in diameter, it's made of 5 VCB75 or VCB100 coax cables.
As Ringram said, Extron is good stuff, Kramer also makes good products.
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