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My D-iLA projector is about 21 ft. from my htpc and I am in possession of a 75ft heavy shielded VGA cable. I actually need almost 45 ft. I figure in order to run in wall out of the way. The cable is male at one end and female at the other so I will need some type of adapter to turn the female to male also.


Now my question is this: Since this cable is so long and since I will have to have an adapter at one end I'm I asking for picture problems? Of course I understand that the longer the cable the more likely degradation is, but since this appears to be high quality cable that is shielded, well what do you guys think????
 

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I feel like half of my posts recently have all been similar to this one, but here goes again. You really should consider making a cable from shielded category 5 ethernet cable as described in this thread. Your signal quality will be as good or better than your 75' cable. The great thing about it is that it is so thin that you can run it -externally- without affecting the aesthetics of your room. I just installed mine last week. I used Liquid Nails to glue it to the corner between the ceiling and the wall (actually just below the crown moulding), and then painted it. Unless it is pointed out, no one would notice that it is even there.

If this would work in your situation, you could get away with a much shorter cable. You could probably sell your 75' cable for a lot more than you'd spend.


- Chris
 

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On this note there are benefits to full-blown VGA cables instead of the Cat. 5 adaptation...all 15-pins are mapped and you can potentially use it for other applications. However, if you don't care about other compatible applications and just want component signals then this is fully adequate.


I sense that Optical Video will be a standard soon...how about the idea of one optical cable to carry both video and audio using some type of multiplexing so we save cabling headaches? http://www.avsforum.com/ubb/smile.gif


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Editor of the AVS Skyworth FAQ and Official Panasonic RP91 Firmware Upgrade Request from OWNERS pages.
 

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The company Comprehensive also sell a VGA Distribution amp but for less than Extron (list is $175.00). We've sold it here for a long time and it works great. Please remember that you must call a dealer to get these items


AJ Abrams

Product Analyst

Projector People/AV Marketplace/Plasma People/Home Theater People/ AVI

 

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Yahoo,


The only thing you're giving up are the Monitor ID pins. When would these be useful? I sort of thought these were vestigial. Especially if you build your cable into a wall, it seems unlikely that you'll come up with other applications for it. Could you explain what you had in mind? I'm curious.


- Chris
 

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As far as the CAT shielded cables go, i will throw out a warning that i did before. With a Cat 5/5e/6 cable, there is a spec called SKEW. this translates into the difference in length from pair to pair. these cables are manufactured with a difference in length from pair to pair. this is done so that the signal (when it is DATA) can reject crosstalk.


this difference is not a factor when talking about 25-35 to 50 foot runs. But it starts to mount up after that. as you get to longer lengths, and higher frequencies (HD, XGA froma scaler) then problems will start to manifest themselves in the area of convergence.


I would suggest that people want to continue preaching this method, that you make some different lengths from about 35' to about 150' and put up a test pattern grid and see if you can see these issues.


If you manage to convince somebody to use this method, and they happily run the cable and terminate them and then hook stuff up after the walls are closed, and they have a convergence error on their 10K plasma... they might be a tad pissed.


Not being alarmist here, just passing on info about how the wire works.
 

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Dizzman,


Agreed. I wouldn't recommend the cat 5 solution for runs over 40'. This is pretty clear in the referenced thread. In this case, he said that his projector is 21' from his HTPC. My point was that since the cat 5 cable is so thin, he could possibly take a shorter route than he would if he has to build it into the walls and be well within the range that the cat 5 works well.


- Chris
 

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The way around the skew problem with Cat-5 or better cables is to buy/rent a cheap Cat-5 checker which can measure distance. Hook up each pair individually to it and note what it measures (anything under 1' difference will be fine). At one end or the other cut ends until you get all the pairs to be the same length.


Connect your HD-15 connector with those pairs already measured and you will be fine (your connector shell might be tough to get together if there is a big difference between them, but at lengths less than 100' feet, skew should be limited to a few inches at worst.


drewman
 

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Drewman,


I was thinking about this too. However my calculations come out a bit differently than what you are saying. Apparently the spec is <45ns skew per 100 meters with a typical skew of about 30ns. 100 meters is 328 feet. 30/328 = .0915 ns/ft. So there would be about 9ns of skew over 100 feet. Propagation time is about 1.5 ns/ft, so this is approximately a 6 -foot- difference. The question I have is : how many ns of skew will cause a noticeable convergance error? With a DILA and Dilard, you can adjust the convergence by one pixel using the Pixel Alignment Wizard which might be enough.


I really think the problem with long cables is more a matter of impedance/ringing.


- Chris
 

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You can buy Extron and others online www.markertek.com. I needed an Extron PD/2 and they had it dropped ship to me. However I had to pay list price. But with no tax and immediate availability from Extron this somewhat makes up the difference of buying from a local dealer which more than likely does not stock any of these items anyway.


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Mark II


[This message has been edited by Mark II (edited 08-10-2001).]
 

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You can find them at www.extron.com or www.altinex.com


David:

I am looking for an amplified splitter, and I noticed the P/2 DA2 PLUS from extron


DA1907SX: 1-in 2-out VGA Distribution Amplifier and

SK2002DA: Sidekickerâ„¢ 1-in 2-out VGA-UXGA Distribution Amplifier Cable from Altinex


Have you had any experience with these products? do you know (around) how much they cost? which one would you recommend.


My setup is something like Laptop to DA +-35'(25' cable +10 foot flexible cable) VGA cable to DA

DA to VC unit (short), DA to Projector +-25'
 

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Quote:
Originally posted by Chris Satterlee:
The only thing you're giving up are the Monitor ID pins. ... Could you explain what you had in mind?
I don't have anything in mind at this moment, but do realize that this is a cable with an HD15 plug...which means if there are other gadgets that try to take advantage of it in the future...unlikely but always possible...


This is just a habit from experience in the IT industry.


I already custom made my own Cat5e HD15 based on the other post, but I personally would not use that if it was going to be PERMANENTLY inside the wall simply because of the flexibility/compatibility issue. http://www.avsforum.com/ubb/smile.gif



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Editor of the AVS Skyworth FAQ and Official Panasonic RP91 Firmware Upgrade Request from OWNERS pages.
 

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Re: CAT 6


The manufacturing process for CAT 5/5e/6 cable leads to a condition called pair skew. Skew exists between pairs when the physical length of one wire pair is different from another. As the transmission cable length increases, the amount of skew increases. Skew affects the displayed image when the differential length between wire pairs exceeds 2 feet, causing the timing of the red, green, and blue video signals to appear out of alignment (horizontal registration errors). A white vertical line on a black field can appear as individual red, green, and blue lines that are close together; the signal transmitted on the shortest wire pair leads the other colors and appears to the left on the display.

CAT 5/5e/6 cable test equipment measures and reports wire pair length. The report on the various pair lengths can be used in equalizing pair skew. The nominal velocity of propagation (NVP — the speed at which the signal travels on the transmission line, measured as a percentage of the speed of light) of TP cable is very close to that of conventional coaxial cable. The similarity in NVP means that an additional length of coax equal to the length of pair skew, placed on the projector’s input, equalizes the effects of pair skew.
 

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I think it is worth noting that coaxial cable bundles are also subject to skew - in fact, I've only ever seen it in such cables. I am using a homebuilt 48' Cat-5e cable and I see no visible degradation of signal versus the 2m NEC cable that came with my VT540.


Gary
 
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