Changing from VGA to DVI

[jblynch4]

Our church currently runs a Sharp PG-F312X projector through simple VGA about 80 feet to the controlling PC. We're experiencing some significant ghosting and a couple or 3 vertical lines running the left side of the screen that are very visible toward the front of the Sanctuary.

Both the Sharp and the newish PC have DVI-I ports; and, we'd like to see if making the switch from analog to digital would eliminate the ghosting.

We're setting up to use the Gefen EXT-DVI-1CAT6 extenders with Gefen DVI cables on the other end of the long Cat6a cable run. Subject to Gefen confirming the desire of our cable guy to run the long cable to a jack then use a patch cable from there as a bit of protection for the long cable as workable, this may be the proposal.

What our Pastor has now asked when I bring the final proposal for approval by Church leadership that I can't answer is what the likelyhood is that the proposal will actually take care of the issue. From the purely technical perspective, I know it can but don't have enough experience to put a percentage to it.

Any input would be greatly appreciated!

Jeff Lynch

[petereit]

Before investing in any new technology, I'd crawl up a ladder with a laptop and a 6-foot DVI cable, plug directly into the projector and display some slides. That would be to make sure your projector isn't just broken. Make sure all your lighting and sound system are powered up and turned on to normal Sunday morning service settings and you're jamming to a praise and worship CD at the same sound levels you run on Sundays.

If the direct-connected laptop gives you the quality you desire, contact your closest Gefen dealer and run your scenario by them. If they agree that the EXT-DVI-1CAT6 units would be a good fit for your issue, find out if they could provide some units for evaluation. If not, ask about their return policy if they don't end up working for you.

[jblynch4]

I almost can't believe I didn't think of that! Thank you and will try same this weekend!

Jeff Lynch

[Stever]

another quick trick is to bring up the projector menus. If they look ok then it may well be the input or the cable as Peter said. That being said keep in mind just the switch vrom VGA to DVI will not make a significant change to image quality when viewed from a distance so keep all your costs in mind when considering that change. As a rule of thumb VGA cable will usually work up to 100' without boosters. Good luck!

[wogster]

Originally Posted by Stever

another quick trick is to bring up the projector menus. If they look ok then it may well be the input or the cable as Peter said. That being said keep in mind just the switch vrom VGA to DVI will not make a significant change to image quality when viewed from a distance so keep all your costs in mind when considering that change. As a rule of thumb VGA cable will usually work up to 100' without boosters. Good luck!

Another point to add to this, have you checked all the connections, lots of times when VGA has problems it's because a connection wasn't screwed together and has partly come apart. The chances of this happening are directly proportional to the difficulty of getting at it to fix it.

Another issue is the VGA cable itself, lots of times when people extend VGA they go out and buy a cheap unshielded extension cable. One thing to remember, the longer the cable, the better the cable needs to be. Ever wonder why the extension cable is no larger then a phone cable, but the cable from the monitor or projector to the computer from the manufacturer is vastly larger in diameter. The reason is that the larger cable is shielded from interference. You want your extension cable made the same way, sometimes that means the cable is $100 instead of $10, and bean counters don't like when people "waste" $90 on a cable, but that is the way things are.

[jblynch4]

...that I've been licensed current in the State of California as a CPA for what will have been 30 years in August! Your real point, however, is not at all lost on me; and, was of further note when tracing back the current cables Friday and Saturday to find the existing cable coming up from the floor right along with the flex to the power outlet where us projectionists sit. While this combination of a rather thick VGA cable that has RCA type audio and video lines sheathed outside of it and run back altogether as one, it was exactly among the factors of interference that I was thinking of that could be contributing to what we experience now.

Thanks for the input everyone!

jl

[wogster]

Originally Posted by jblynch4

...that I've been licensed current in the State of California as a CPA for what will have been 30 years in August! Your real point, however, is not at all lost on me; and, was of further note when tracing back the current cables Friday and Saturday to find the existing cable coming up from the floor right along with the flex to the power outlet where us projectionists sit. While this combination of a rather thick VGA cable that has RCA type audio and video lines sheathed outside of it and run back altogether as one, it was exactly among the factors of interference that I was thinking of that could be contributing to what we experience now.

Thanks for the input everyone!

jl

Are the RCA cables shielded? Guarantee that the power cable isn't. People often put cables through a common hole in the floor, that were never intended to go through a common hole in the floor. Depends on what the floor is made of and what's below it. If it's a wood floor and you can access the bottom without breaking holes in a ceiling, then you should see what's running below and drill a couple of additional holes, no closer then 12" apart. Run the VGA through one hole, the RCA through another, leave the electrical where it is. If you can't access below without busting through drywall then you may want to make an access port and drill the additional holes anyway. An access port is basically a small door that you can open to access the wiring. They make covers for when you make holes in drywall for plumbing, one of those would probably work fine for your purpose. If the ceiling is lath and plaster, you don't want to touch that, it's horribly expensive to fix and an access port may not work well because you need to cut the lath so you need a frame around it to support it. If the floor is concrete, then it would need to be X-rayed to see what is inside it, before drilling holes in it, sometimes the run wiring and water lines inside concrete and there is often rebar.

[Brad Weber]

Originally Posted by wogster

Ever wonder why the extension cable is no larger then a phone cable, but the cable from the monitor or projector to the computer from the manufacturer is vastly larger in diameter. The reason is that the larger cable is shielded from interference.

Both large and small cables probably use coax cables for the red, green and blue signals and coax or twisted pairs for the sync signals, so the shielding and resistance to external RFI and EMI may be about the same. The difference is probably more in signal loss and larger conductors typically relate to lower signal loss. In addition, signal loss varies with bandwidth, which is in turn resolution and scan/refresh rate dependent, so accommodating higher resolution, higher refresh rate signals means using lower loss cable. That is likely why a video card or monitor comes with a larger VGA cable, the manufacturers want the cable they provide to be able to support good image quality at the highest compatible resolution and scan rates for their devices.

Originally Posted by jblynch4

While this combination of a rather thick VGA cable that has RCA type audio and video lines sheathed outside of it and run back altogether as one, it was exactly among the factors of interference that I was thinking of that could be contributing to what we experience now.

Is it an actual manufactured VGA cable, in other words with a premolded HD15 VGA connector on both ends? Does it happen to have any marking as to manufacturer or model?

That the VGA cable runs next to power for a limited distance is not unusual, if it runs right next to power all the way out to the projector might be. But before you go blaming the cable, you might want to make sure the computer and projector are adjusted for the optimum image quality. For example, your projector is native 1024x768 resolution so it would be best to have the computer output that resolution. You could run the computer at a different or greater resolution but the projector than has to process that to its native 1024x768 resolution anyways so there is no real advantage, and potential disadvantages, to doing that. You might also want to clock at the clock and phase adjustments on the projector (in case you don't have it the manual can be found at http://www.projectorcentral.com/pdf/...anual_4209.pdf). It may even be as simple as a connector not properly seated. It makes sense to try to eliminate as many of those factors as possible before investing in a different cabling approach.

A little off topic but one common potential issue with manufactured VGA cables in permanent installs is that because they are rarely run in conduit it may be important to make sure the cable is properly rated to be run in walls or above ceilings or even possibly through plenum areas. There are properly rated cables readily available but the VGA cable you buy at the computer store may not be properly rated for permanent installations.

[jblynch4]

First-to Steve

I have worked through most of the projector menus. I made one adjustment to get some more brightness-one person actually asked if I'd made the fonts smaller. I found it odd that I couldn't seem to get off the menu line into the sharpness adjustment in computer mode though even if I had-am not sure that would address the vertical line I now seem to notice on the left edge.

2nd-to wogster

Connections are solid-if odd. The projector side is screwed in tight. The output side is terminated VGA at it's end but then simply pushed into another VGA cable that screws tight to the GT220. There's nothing loose anywhere. The long-run VGA cable is rather thick-between 1/4 to 1/2 and inch though it looks anthing but standard. The RCA type cables that run back with the VGA are very standard thin ones. They were placed in a sheathing outside of the primary VGA cable and run back as though they were one. The power cables in the flex that run to the power outlet are the normal power cables-just run in standard flex. The wood floor of the AV booth is raised up from the cement foundation. There's just a simple cutout at the point where the flex and the VGA cable come out-the flex going to the outlet mounted on the inside wood surface of the booth and the vga cable just coming up and laying down on the carpet. If we run this new Cat6a line, we're going to be much more careful!

to Brad Weber

The existing long-run VGA cable looks as though it was field-terminated with standard aluminum connectors. I don't think there would have been room enough in the ceiling-mounted projector stand pipe for the VGA connector to fit. I didn't happen to see any markings on what's visible; and, with the added sheathing for the other 2 cables, there wouldn't be anything to read-just black. I did take time last Saturday on resolutions. The PC monitor is native 1280x1024 and the projector 1024x768. Changing the projector reduced the image size. Changing the PC down really degraded the image.

As to the Cat6a cable we might run, good points and it's good that we have a member working for a large cabling company who will be doing this part for us. The other interesting confirmation coming from Gefen was that their extenders do want connections end-to-end on the very same cable-no jacks or patches.

for all and Peter...

I am setting up for testing after Bible Study Thursday using the new laptop we authorized for our Pastor's wife using an HDMI-DVI cable to be delivered from Newegg tomorrow. This will be interesting!
jl

[jblynch4]

Thanks first go to Peter for suggesting the test! I've ttached 3 pictures that show the results from last night. The number 8 simply shows the extended image from the Pastor's wife's laptop connecting from the 15' DVI-HDMI cable dropped directly from the projector. Number 12 is a recent slide about evangelism-projecting off the current VGA run to the PC in the AV booth. Number 14 goes back to the same slide running off the laptop. The differences are significant. While there could be a number of reasons that obviously include the only 15' distance for the DVI test, the differences are significant enough to prove that going digital would make some sense.

I appreciate all the feedback received from the community this week and pray that this will just be a start of many visits down the road.

In Him,

jl

[petereit]

That's why we run all our video signals over SDI and use SDI-to-HDMI converters at our projectors. Once we saw that crisp, clean, beautifully saturated, completely interference-free picture over 200' of SDI cable, we realized it was SO worth the investment in the converters. And considering how many power cables and noisy lighting fixtures we had to run our SDI cables with/across it's absolutely miraculous.

[wogster]

Originally Posted by petereit

That's why we run all our video signals over SDI and use SDI-to-HDMI converters at our projectors. Once we saw that crisp, clean, beautifully saturated, completely interference-free picture over 200' of SDI cable, we realized it was SO worth the investment in the converters. And considering how many power cables and noisy lighting fixtures we had to run our SDI cables with/across it's absolutely miraculous.

Okay, dumb question number 18,446,744,073,709,551,616 or thereabouts what does SDI stand for, and a can you convert from VGA to SDI then SDI to VGA for less then an arm, leg and first born male child....

That's the easy part, now comes the hard part, anyone know of a good source for this stuff in Canada. Often I see stuff like this and it's $9.95 in the US and but the time it gets to my door in Canada it's the better part of a C note because of shipping and customs fees.