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Author Topic: 250ft VGA cable run?  (Read 2533 times)

Kyle Malenfant

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250ft VGA cable run?
« on: March 10, 2013, 06:03:06 pm »

Hello,

I need to make 2 runs of video cable, each run consisting of a McBook pro and projector.  One run is 325', the other is 250'.

The application is a theater-like show in a university gymnasium.

I currently own enough VGA cables to cover the distance, though my inventory is made up of 50ft sections.  Some are male to female, some male to male (where I can use gender changer adapters).  Brand of cable is QVS http://www.jr.com/qvs/pe/QVS_CC320B50/ and Comprehensive http://www.bhphotovideo.com/c/product/632891-REG/Comprehensive_HD15P_P_50ST_50_15_2_m_Standard.html

I also own two Kramer VP200K distribution amplifiers..intending to use one per run.

The projector is 3500 lumen and the screen is approx 12' diagonal 4:3 aspect ratio.

I've done a bit of research here on the forums and there is a lot of chatter about RGBHV and/or CAT5 as options for long run though I'd like to utilize my current inventory if possible to keep costs down.

  I'm unsure of the resolution of the content provided by the client (won't have it till the day of the event), though I understand this factor has an impact on the answer to my question.

Would I benefit from purchasing longer runs of VGA cable reducing the amount of times I need to use an adapter?  Will the DA push my signal far enough with little loss in image quality?


Thanks for your comments.
Kyle
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Bojan Bajsic

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Re: 250ft VGA cable run?
« Reply #1 on: March 11, 2013, 02:47:43 am »

theoretically it should work, but:

- try to get the number of 'joints' down, especially if they are exposed you get noise on the line and you really don't want intermittent drops
- you will probably be stuck with regular vga resolutions so 5:4 @ 1280x1024 or 4:3 @ 1024x768 or somesuch
- make sure all your joins are of the screwy variety (i also usually stage tape them together also)
- make sure the cables run nowhere near lighting or electrical ducts or cables
- make sure he brings a VGA adapter for the mac
- it really doesn't hurt to make a test run before, just connect all the cables into a 300ft pile and put a laptop next to the projector and see what happens. Aside from the situation of running next to a bunch of electrical or dimmer cable, it doesn't make a difference if the cable is running flat on the ground around the whole house or if everything is in the same place.
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Brad Weber

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Re: 250ft VGA cable run?
« Reply #2 on: March 11, 2013, 07:10:40 am »

It appears that your DA provides gain to offset the two-way split but does not seem to offer any other gain or peaking/EQ adjustments.  With a 250' to 325' runs of VGA cable consisting of multiple smaller lengths and adapters and with a Mac via a VGA adapter, if at all possible I would want to test it with the actual projectors and computer to be used before committing to it.
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Dave Rickard

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Re: 250ft VGA cable run?
« Reply #3 on: March 11, 2013, 12:47:19 pm »

On a different note: Is the room darkened or lit?  You may find 3500 lumens inadequate for that screen size in a lit room, regardless of your cabling.
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The wrong piece of gear at the right price, is still the wrong piece of gear.

Bojan Bajsic

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Re: 250ft VGA cable run?
« Reply #4 on: March 11, 2013, 01:32:58 pm »

True about the Kramer, the unit you have is not a "true" distribution amplifier/line driver, as it lacks any level gain or eq. Still you might try it out, but put it in different places (like try once with the DA after the first 50ft cable, then try once with the DA at the 150ft mark...).

But in any case, like mentioned in the previous posts, try it before with a real computer connected to a power outlet.
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Kyle Malenfant

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Re: 250ft VGA cable run?
« Reply #5 on: March 11, 2013, 02:06:41 pm »

So I tested out the run today, though didn't have access to the projector I'll be using on the job so I used a 42" LCD (maybe my results are skewed by this when compared to the projector?)

Signal chain is as follows:

MacBook pro (late 2012) => Apple thunderbolt to VGA dongle => 6x 50ft. VGA cable => Screen



- you will probably be stuck with regular vga resolutions so 5:4 @ 1280x1024 or 4:3 @ 1024x768 or somesuch

The native resolution of the screen is 1024x768, though in this run the color seems to be more red than it should be and the image is not crisp.  I tried 800x600 and while there was low resolution, and the screen was a little stretched, the color was more normal.  Same goes for 1280x1024...color normal, stretched, a bit fuzzy/soft images.

Brad and Bojan, you were both correct in that my DA sis nothing to help the issue.  Is there an in-line booster I can use?  Would the Kramer VP-2L do the trick?  http://www.kramerelectronics.com/products/model.asp?pid=589&sf=25

On a different note: Is the room darkened or lit?  You may find 3500 lumens inadequate for that screen size in a lit room, regardless of your cabling.

We did this event last year, using the same screen and projector and it worked out great.  The house lights were almost completely off and the clients were pleased with the video output.

Last year our AV booth was set up just off of stage right, this year we are in the back of the house and need to do a much longer cable run for sound, DMX, and video.

If the Kramer VP-2L is not the best/recommended fix for my scenario suggestions are more than welcome.

Thanks for all your guidance, I really appreciate it. 
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Brad Weber

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Re: 250ft VGA cable run?
« Reply #6 on: March 11, 2013, 02:44:45 pm »

The native resolution of the screen is 1024x768, though in this run the color seems to be more red than it should be and the image is not crisp.
That definitely sounds like line losses, peaking/EQ should help with the color and the overall gain with the image quality.

The DA you have and then a line driver like the VP-2L for each run would be great as you could independently adjust for each different run length.  Something like http://www.kramerelectronics.com/products/model.asp?pid=1488&sf=8 would combine both functions in one but you have to adjust it for a best fit compromise for both projectors.
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Kyle Malenfant

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Re: 250ft VGA cable run?
« Reply #7 on: March 12, 2013, 01:52:33 pm »

That definitely sounds like line losses, peaking/EQ should help with the color and the overall gain with the image quality.

The DA you have and then a line driver like the VP-2L for each run would be great as you could independently adjust for each different run length.  Something like http://www.kramerelectronics.com/products/model.asp?pid=1488&sf=8 would combine both functions in one but you have to adjust it for a best fit compromise for both projectors.


Thanks Brad!  I'll pick up a couple of the line drivers so I can tweak the EQ individually for each run.  I'll re-post after the job and let you know how it turned out.
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