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A while back there was alot of talk about using Cat5 for longer runs instead of standard VGA cable. Would it be possible to use Cat5 with a VGA splitter to get more than 25 or 50 feet? I am trying to distribute the audio/video from the HTPC to all rooms in the house and would rather use Cat5 cabling!
 

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You can send RGBHV/VGA signals over CAT5, also called UTP (unshielded twisted pair). It is better to use CAT5e or CAT6 cable. There are several manufacturers that make UTP transmitters and receivers. CAT5/5e/6 cable is inexpensive, but the transmitter/receiver pair will cost quite a bit. Most UTP TX/RX do have a minimum distance for cable runs. In some cases your minimum cable run must be 50 feet. Here is a web address to a UTP TX and RX.


Transmitter (TX) http://www.extron.com/product/product.asp?id=tpt15hda


Receiver (RX) http://www.extron.com/product/product.asp?id=tprbnca


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-Serlin
 

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I'd suggest doing a scale floorplan drawing, then centrally locating the VGA splitter in attic or crawlspace and seeing if maybe you can't reach each room with a run of no more than 50 feet. As Serlin says, the transmitter/receiver pairs will be expensive, and you'll need a pair for each room.


The cheap alternative would be to use Cat5e shielded in unbalanced mode with HD15 connectors as we have been doing since the original message - I can testify that technique works out to 48 feet.


Gary


[This message has been edited by Gary McCoy (edited 10-03-2001).]
 

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The extron products mentioned above don't work like the DIY cable discussed in the past on this board.


Extron takes the RGBHV signal, turns it into a balanced higher voltage signal with one box and then turns it back into RGBHV at the other end with another box. It automatically equalizes the signals to any normal line losses. This kind of Cat 5 RGBHV doesn't require STP, only UTP.


I have personally tried out that extron box for both NTSC video and RGBHV. Both work to about $1000 and work through patch panels just fine. The only problem with going that far in RGBHV is that the different pairs of wire are different lengths and you have to add cabling to delay one signal so it matches up with another on very long runs (i.e. over about 300 feet).


Standard video and s-video looks very good through it and it also sends audio.


drewman
 

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Quote:
Originally posted by midi-guy:
Use STP (Shielded Twisted Pair) Cat5 Cable , not UTP.

I found that on lengths over 30 feet, that regular CAT5 UTP cable introduces ringing problems etc.
I also tried to make a 26 feet long VGA cable using STP cat5. Unfortunately, I get some (though not serious) ghosting in running at 1024x768 resolution. I disappoint that it's different from the others' experience that the image should be flawless if it's made under 40 feet.


Do you have any idea what's wrong, or simply I use some taiwanese LANS cable instead of the famous Belden ?


K.Kwok
 

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For the purposes of the DIY cable, use shielded twisted pair (STP) instead of unshielded twisted pair (UTP). The shielding will cut down on interference.


Also try to keep the signal and ground of each component on the same pair. Any interference introduced on one wire then will be on the other and will effectively cancel each other out.


drewman
 

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I am already using STP and keep the signal (RGB) and their ground on the same twist pair. The ghosting is just there.


Just want to know whether you get a perfect image (without ghosting) at or over 26 feet?

If it is achievable, I would rather buy a better (e.g. Belden) cable and try again. Except cable quality, I can't think of any other reason for the difference.


K.Kwok
 

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Use STP (Shielded Twisted Pair) Cat5 Cable , not UTP.

I found that on lengths over 30 feet, that regular CAT5 UTP cable introduces ringing problems etc.


AO.
 

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This may or may not help your situation.


Ghosting is generally associated with poor termination and/or poor quality cable. Always go for the good cable!


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-Serlin
 

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Oh, one more thing. Computers (if you are using one) are not meant to drive their video signal any further than their local monitor. You can usually go farther, but may have noticeable signal degredation over 15-feet. Computers will vary quite a bit in their ability to drive a signal and 15-feet is worst case. The higher the resolution the shorter the distance before degredation. Amplification with coax cable or a Transmitter/Receiver for STP or UTP is still a good idea for acheiving the best possible image with your 26+ foot run.


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-Serlin
 

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Quote:
Originally posted by K.Kwok:
I am already using STP and keep the signal (RGB) and their ground on the same twist pair. The ghosting is just there.
What is the make and model of the baluns you are using?


-Ted-

 

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CAT5 cable is not intended for analog use. With these accessory boxes that do equalization and convert to differential signaling, you may get better performance, but just because CAT5 is used for 100Mbps data signals doesn't mean that it is better cable.


First of all (and primarily), data transmission schemes use loads of equalization, both in the analog and digital regimes to achieve good bit-error rates (good signal quality). The cable itself is horrible.


Second, there will be an impedance mismatch that will cause your ringing. It isn't a bad cable, it's just designed for something different. TV and monitors use 75 ohm impedance and that is a function of the wire, cladding, and shielding used. Old-style ethernet (and most of the RF world) use 50 ohm impedances. I believe 10baseT and 100baseT standards use 100 ohm terminations. The mismatch will not only cause a loss of absorbed power, but also cause reflections which will lead to ringing. The severity depends on several factors.


Bottom line is that CAT5 cable is not great stuff. Certainly no better than any cable designed for video transmission UNLESS the CAT5 is combined with some sort of box that handles the conversion between what is good for video cable and what is good for CAT5.



Jake
 
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