VGA cable length for university lecture hall - AVS Forum
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post #1 of 10 Old 11-20-2013, 03:23 PM - Thread Starter
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I've been researching what would be a maximum length for a VGA cable to run from a laptop to a projector and I get different lengths depending on the responder. We have been having issues with one of our lecture halls and its outdated equipment. There are times when the projector doesn't get a signal from the different laptops that are being used. The podium that houses a lot of A/V equipment has some sort of box that accepts the VGA cable and outputs it to some BNC connectors that connect to a component in a rack inside the podium. An LCD panel that is also very out dated used to control what A/V device was being used. However it no longer plays a role in how the projector functions.

I'm assuming the source of this inconsistent performance is this funky box. I would like to bypass this box with the BNC connectors an run a VGA cable directly to the projector's D-Sub 15 port from the podium where the laptop VGA cable would connect. There would be a D-sub 15 coupler at the interface on the podium. The cable run from the podium to the projector room we estimate is probably 60' or more. I haven't measured it exactly. Plus it would have to run in the wall and ceiling to get to the back of the hall where the projector is.

Everything I've read on AVS Forums so far says used "good quality" VGA cable but what exactly does that mean? And would I need to use a booster amp? I would need to recommend something to our facilities guys.


Thanks
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post #2 of 10 Old 11-20-2013, 06:33 PM
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At 60' you should be fine.  I've sold 150' "good" VGA cables that were still relitivly cheap and they didn't have a problem.  You may need a booster, but I would doubt it.  All you can do is test it.

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post #3 of 10 Old 11-21-2013, 10:40 AM - Thread Starter
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Thanks for the reply but what defines "good" VGA cable? There are so many to choose from.
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post #4 of 10 Old 11-21-2013, 10:55 AM
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One that contains at least 3 75 Ohm coax cables
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post #5 of 10 Old 11-21-2013, 07:42 PM - Thread Starter
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Where is the best placement for the Amp Booster if one is needed? Would it be worthwhile to use one as insurance?
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post #6 of 10 Old 11-22-2013, 08:02 AM
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Not all laptops have the same signal level, especially when running off battery power only. It sounds like the current setup is correct, when running longer distances it is common to convert a "VGA" plug to 5BNC or RGBHV using an interface. Converting to individual coax cables can generally run a longer distance than standard VGA cable, and the interface has built in ciruitry to amplify the signal.

I would inspect all the cables and connections and replace if loose or worn out. If your signal level is still too low, replace the interface device that converts VGA to BNC. You can find used units on ebay for about $25 such as
http://www.ebay.com/itm/Extron-RGB-130xi-Universal-Interface-w-ADSP-26-567-02-MVGA-M-M-6-Analog-Cable-/171105406225?pt=LH_DefaultDomain_0&hash=item27d6ad4d11

You would want to place the amplifier on the source end, maybe in the podium.

Good luck,

Eric
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post #7 of 10 Old 11-22-2013, 11:50 AM
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Quote:
Not all laptops have the same signal level

they should, it's a standard 1Vp-p. Sync signals are TTL level.
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post #8 of 10 Old 11-26-2013, 11:06 AM
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I disagree, especially battery power vs AC adapter power or when trying to send image to both laptop LCD and VGA output at the same time. Maybe they should, but not all do!

Eric

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Originally Posted by SAM64 View Post

they should, it's a standard 1Vp-p. Sync signals are TTL level.
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post #9 of 10 Old 11-26-2013, 11:16 AM
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You disagree that there's a standard?
We'll have to agree to disagree.
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post #10 of 10 Old 11-29-2013, 07:49 PM
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When you say (OP) that there is no signal getting to the projector from the some of the laptops, do you mean a degraded signal (low brightness/contrast/ tearing image )or no signal period? Are you aware that laptops need top have the VGA output enabled via keyboard command?

I have purchased several hundred 100ft, well made, VGA cables from QVS. Not had a bad one in the bunch. Inexpensive as well.
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