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Anonymous Poster

Assembling RGB Cable

02/20/2008 1:29 PM

I am trying to assembly a RGB cable with 15 meter to connect my computer to a plasma TV using a cable with 8 pairs and shield. But the image is not good. A little bit shaking. How can I solve it? If I use a cable with shield in each pair, will be better?

Thanks in advance.

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Engineering Fields - Electrical Engineering - New Member United States - Member - New Member

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Location: Wichita, Kansas USA
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Re: Assembling RGB Cable

02/20/2008 3:25 PM

What input are you using on your plasma, and what is the output on the PC? Typical RGB monitor cables would have a separate shield/return for each color and sync signal.

The best interconnect from PC to plasma would be DVI out on PC, to HDMI in on the plasma.

With either method, your 15 meter length is going to require you to have a decent quality cable to prevent shielding and loss issues.

If you are in the U.S., a place called has just about anything you can imagine, and the cost is less than I would spend to build it myself.



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Re: Assembling RGB Cable

02/20/2008 5:06 PM

Are attempting this with HD15 (VGA) connections or BNC (3 wires of R, G, B respectively). Unless it's the later, I wouldn't expect anything but poor results--especially if there is any interference on it's way to the panel.

You're video card may provide HD15 to BNC, or even component video, and that could yield results with RG-6, too but this is depended on the computer's video card as component video is not RGB-based but rather Y,Pr,Pb. With BNC, you can use three shielded RG-6 runs and probably be OK.

Finally, if you have the option of DVI or HDMI and image quality is that important, plunk down the money to get the cables, though.

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Re: Assembling RGB Cable

02/21/2008 12:10 PM

If you want to use UTP (Cat-5), there are driver chips made by Analog Devices, Intersil, Maxim, and others that make this possible.

Search their sites using Cat-5 and video and you will get plenty of hits.

Good luck with your quest.

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Re: Assembling RGB Cable

02/22/2008 8:25 AM

Why not use an rf wireless transmitter and receiver?

For the distance you want they work well, as the others have said cable should really be avoided over that distance for picture quality reasons.

They are now very cheap and can easily be connected to either end... Most even include a separate rf connection to send the infrared remote control signal!!


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Re: Assembling RGB Cable

02/23/2008 4:27 PM

The short answer is that the cable drivers have limited driving capability. The cable is not allowed to cause much frequency dependent amplitude drop or phase shift. And these are obviously quality and length dependent. High quality cable building is not for amateurs. While Ethernet, fibre etc. have long acceptable lenght, video is not one of them. Here is the long answer.

HDMI uses three data channels to transport data to the video screen.
Each channels cable is a shielded twisted pair, they transmit sing what
is called a TMDS (transition minimized differential signalling)
signalling scheme. This is quite similar to the LVDS used in notebook
screens, in USB and in PCI-E. There are various different revisions of
the spec that use different data transfer rates on these channels. If
you are using 1080p then the cable bandwidth needed depends on colour
depth, the HDMI org website explains it. For higher resolutions more is
needed for 1080i (interlaced) only 75MHz is needed.

The HDMI people lay out a specification for the cable. There are two
specs actually, from their website:-
"Recently, HDMI Licensing, LLC announced that cables would be tested as
Standard or High-Speed cables.

* Standard (or "category 1") cables have been tested to perform at
speeds of 75Mhz, which is the equivalent of a 1080i signal.
* High Speed (or "category 2") cables have been tested to perform at
speeds of 340Mhz, which is the highest bandwidth currently available
over an HDMI cable and can successfully handle 1080p signals including
those at increased color depths and/or increased refresh rates.
High-Speed cables are also able to accommodate higher resolution
displays, such as WQXGA cinema monitors (resolution of 2560 x 1600)."

You probably should use High Speed cable since the bandwidth of 1080p
signals with 12 bit colour depth is high enough to warrant it.

I wouldn't though spend a great deal of money on the cable. This is not
a particularly difficult cable to get right, I expect most manufacturers
have got it right. It is a bit more important though than for things
like USB, USB has retransmition to deal with error and error correction.
HDMI has error correction on audio and auxiliary data but does not have
much on the video signal because of bandwidth limitations. Still, I
expect most cables are good.

Regarding connectors, I wouldn't worry too much where a cable is made
up. More important is whether its made by humans or by machines.
Cables should be attached to connectors by machines, humans are too
error prone to do the task well. Get a cable with connectors on that
looks like they have been machine attached (normally ones with strain
reliefs very closely fitted to the cable or bonded with it are machine
attached or at least semi-automated).

Do you have a long cable run? If so then cable quality will matter

Anonymous Poster
In reply to #5

Re: Assembling RGB Cable

04/11/2008 2:24 PM


I have answered your Post/comments,

Generally best to use the Cable Maker of your particular cable, but try:

If you are still needing help, reply with

Kind Regards....

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