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Component Cable Length

Discussion in 'Plasma TVs' started by Claus, Jan 29, 2003.

  1. Claus

    Claus
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    Hi!

    Lots of questions today....

    How long can a component cable be in length before the quality of the signal
    gets weaker?

    Thanks,

    Claus
     
  2. dgj

    dgj
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    As long as you want, length makes no difference.

    The signal does not slow down going up hill or round corners:D
     
  3. loonatic

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    Surely that’s not correct…what if the cable was several hundred feet long !!

    Ideally the cables should be as short as possible.

    Most component cables I’ve seen come in 1,2 or 3 meter lengths.

    Cheers, Lee
     
  4. dgj

    dgj
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    The speed of a signal going through a 1 meter cable will be the same as that going through a cable hundreds of meters long.

    But let's be realistic as the normal cable used is about 3 meters max to 1 meter min depending on the position of your equipment, there will not be any difference in the signal strength. What will affect the signal is the quality of the cable, so buy the best you can afford, as a rule of thumb spend on cables 10/20% of what you spent on the equipment.
     
  5. torrent

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    I'm no expert but would expect that length would eventually cause some loss to the signal. However, that length is probably significantly longer than you need worry about. If you buy a good quality Component Video cable which is, say, 5m in length, then I would expect that cable to be of sufficient quality in its construction to support a good signal over that distance. I guess a good cable would have the following characteristics:

    - Thick well-shielded cables
    - Oxygen Free Copper (OFC).
    - 24k gold plated all metal connectors.

    Well waddaya know. You can find them here http://www.rgbtosvideo.com (although perhaps not of the length you require). I did see some around on another site (I forget where) which ranged in lengths.
     
  6. TheBigApple

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    I use Coaxial cable of an average quality for installation of CCTV equipment and it usually starts to lose picture quality after about 300m.
     
  7. DJP

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    The subject of cables length can be rather tricky. In an ideal world you would be able to buy a cable with the precise impedance, velocity etc to match your source and destination requirements with 0 added capacitance per metre and 0 group delay etc. In practice a compromise has to be reached.

    If the cable length was short enough then a grotty piece of bell wire could be used to connect pieces of kit together (it might radiate a bit though). In practice if the rise time of the fastest signals you are looking at can fit within the length of cable then you should be looking at an impedance matched cable. For Video applications this normally means 75Ohm cable is needed for anything over a foot or 2.

    Once the impedance has been decided on you have to look at things like, resistivity, capacitance/m, skin effect, group delay etc. It can be a really thorny subject.

    However, in essence the longer the piece of cable the more you will see group delay begin to effect the quality of the signal and resistive effects reduce the amplitude. Amplitude is pretty obvious, the signal will get smaller and the picture dimmer. Group delay is where signals of different frequencies get delayed by different amounts resulting in a slight smearing or blurring of the signal.

    How long can you go? Well it depends on the quality of the cable. In my experience a reasonable quality screened cable should be good for a few m's say up to 5m depending on the brand and price paid. If you want more than that I'd really start looking at the higher quality brands. After all if you've spend 1000s on a Plasma it seems churlish to compromise on the cables as well.

    As with all things though it is subjective. While group delay and amplitude can be measured, whether you can actually see the effect will depend on your specific environment and your eyeballs.
    :D

    Derek

    edited for pesky typos
     
  8. Joe Fernand

    Joe Fernand
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    Claus

    Your looking at only one 'component' in a system in isolation - any cable must have an effect on the signal and certainly a longer cable is going to have more effect than a short cable.

    You have to consider both the affects of a long cable on your signal and the video output stage of your source devices ability to drive a long cable.

    On 'most' consumer kit you can safely go to 10m without too much trouble - assuming a decently designed output stage and a good quality video cable; we use Van Damme broadcast video cables.

    We have supplied 15m Component video sets on occasion and the customers have also found these to be acceptable.

    If you need something any longer than 10m I'd say its a matter of trying it out for your self and if you have a significant signal drop off you may have to consider some form of signal amplifier - we use these all the time on installations where you can be firing video signals over long cable lengths and in fairly 'electrically' hostile environments.

    Best regards

    Joe
     
  9. Reiner

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    As long as you want, length makes no difference.

    The speed of a signal going through a 1 meter cable will be the same as that going through a cable hundreds of meters long.


    Not correct. The longer the higher the resistance and thus the losses and thus degradation in picture quality. The speed of the signal is of no importance here though it is correct to say it won't change.

    If you want to try just buy some cheap SAT cable (75 Ohm) at the length required and a handfull of RCA connectors, given you are handy with a soldering iron.
     
  10. dgj

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    This same argument is going on over at the Amplifiers and Receivers section. Look for the thread "Same Length Speaker Cable" where the same point is being argued in respect of speakers.
     
  11. Phil_Yeoman

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    For anything over 10m you should be lloking at balenced imput and ouputs where the effects of crosstalk and interferenec pickup are substantially reduced. I actually do this for the run from my video processor to my projector where the cable rum is 13m.

    Phil
     
  12. ncpl

    ncpl
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    Given all of the above about quality cables vs length etc, I am debating my cabling choices and length matters (as always):-

    All hi-fi components currently sit in an adjacent room to lounge and are fed into lounge via a small and discrete hole in the wall. The video cables currently are 10m to screen. The quality of these was completely fine into my Aconda 32" (great TV)

    When I install the plasma, do I:

    A) put the tuner (assuming I get one with) close to the plasma and continue with the long runs to the tuner, or

    B) put the tuner with all the source gear and run a 10m tuner umbilical to the screen

    I know A) will work, but, with B) I don't know about the output from a tuner and the type of cable used.
    If it's a tuner then it'll be the Hitachi.

    I'm assuming that 10m of umbilical is cheaper than 10m of good quality Component (which is the bit I don't have). B) also means less cables into the lounge.

    Anyone with experience of long runs from a tuner ?

    Cheers

    Nick
     

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