VGA cabling for projector install

[Dave]

Hi guys,

 

I have a projector install coming up and would like you to check my thoughts about cabling.

 

It will involve a couple of 40m or so VGA runs to a projector.

 

My gut instinct is that the losses over regular VGA cables will be too great, and so I'm planning to do it with five-wire (RGBHV) using decent-sized coax and the Ikon VGA-BNC adaptor PCBs (see here if you're not familiar with them).

 

However, I was wondering if mini-coax (5 x RG179 sort) would be sufficient over this length. I don't have enough experience with it to say for certain - the companies I work for use full-sized 5-wire on shows. Whilst the core size of RG179 is similar to VGA cable, the advantage is that the syncs will be on proper coax, as opposed to twisted pairs. However, losses could still be an issue.

 

Also, I've noticed that SDI cable has similar losses to PSF1/3, but is thinner and cheaper. I see no reason why I couldn't use it (and you can get multicore versions), but it's not something I've done before.

 

It's also worth noting that the client wants to be able to plug a laptop directly in to my cabling (without using a VGA DA or buffer), and again, that makes me tend towards bigger cable as the VGA outputs on laptops don't have as much "drive" as desktops in my experience.

 

Any advice greatly appreciated - I don't want to over-engineer the job if it's not neccesary.

 

Thanks,

 

Dave

[stillgoingstrong]

Hi,

 

If you are only after a single connection point, then I would try running a 40m VGA cable. We do it on a regular basis (around 20 a year) and if that gets shadow on it, try picking up a CAT5 convertor kit from the likes of CPC. They're useless for touring, but faultless if left alone on an install. They only cost around £50 and CAT5 cable is nice and cheap. We've done multiple runs of up to 150m with these things with no issues at all with the image. It's purely their ability to stand up to the abuse of touring where they fail.

 

If you're concerned about them plugging in, you can get right angled VGA face plates that allow you to plug a VGA straight into the inside of the plug in point. Very handy to stop people breaking a male connector left lying around and requires no re-wiring/solder. It also means if they do bust the jumper cable they only have to replace a 2m (or so) jumper cable rather than the whole 40m etc.

 

Hope that helps

 

Phil

[KevinE]

I would also recommend the CAT5 converter solution if only for the reason that the cables are easier to terminate, cheaper, neater and easier to thread through holes etc!

 

I sometimes see shadowing or ghosting on VGA over only 5 metre runs or so if the cable's a little cheap, plus it might look ok one one screen res but as it changes mode the higher frequency may make the ghosting more visible.

 

The CAT5 method will usually also eliminate hum loops which may only manifest on certain makes of projector.

[Dave]

try picking up a CAT5 convertor kit from the likes of CPC

Are you referring to CPC part CS10932 (catalogue page 891)? It costs £56.52+VAT per tx/rx pair.

 

Most other VGA over cat5 boxes cost about £200 or so per pair, so I'm a bit suspicious about its quality. But from your post it sounds like it works OK.

 

Anyone else tried this item?

 

Thanks,

 

Dave

[pstewart]

Are you referring to CPC part CS10932 (catalogue page 891)? It costs £56.52+VAT per tx/rx pair.

 

Anyone else tried this item?

 

I've used this product in a few different places at work, and when it works it's great, however it seems susceptible to noise on the mains supply (e.g. nearby fluorescent light switching on/off) which causes the picture to go purple, and has to be rebooted to reset it. We have three sets of them and it seems to affect all of them.

 

If it were me doing the install, I'd go for real VGA cable (either 15pin or 5BNC) over catV - much less to troubleshoot. If only my soldering was up to doing 15pin Hi-D connectors :blink: .

 

Philip

[soundo26]

If you use 40m runs of VGA cable without amplification via a DA you will be lucky to get away without appreciable signal loss resulting in drab images with lack of colour and ghosting and aberrations especially on vertical risers of text, this is caused by severe reductions in bandwidth & voltage.

I cannot understand why you would want to do this without using the correct equpment which is designed to do the job. If it's a cost issue you can try the cat5 option. You obviously know that your suggestion is not correct so why do it?

 

The VGA signal was only ever designed to run from your computer to it's monitor, it will run further depending on the quality of cable & connectors used but pushing it to that sort of distance is way outside the design parameters.

 

It never ceases to amaze me that people are always trying to cut corners in this industry resulting in an unprofessional job via unprofessional attitudes. Why do you think Distibution amplifiers are manufactured? Why the aversion to using them, especially in an installation, you may get away with it for one job and it won't work on another!

 

Whether you accept the image that comes out at the end is up to you, you will certainly get an image, will it be you who has to justify to a p*ss*d off client why the image is soft/not bright enough/out of focus/jittery or blurred, I guess not!

 

If you wish to call yourself a technician, for all our sakes do the job right in the first place, I for one am totally cheesed off with sorting out your collective problems when going into venues installed by people like yourself in the way that you are suggesting!

[scottmcleod]

I just had a 5500 Lumen projector installed into my theatre with 3 RGBHV (VGA) inputs, a switcher, etc...

 

They used those balancing transformers that use CAT5 cable (ethernet) for the actual transmission of the line data. Estimated 200m reliability. Boxes weren't cheap (100$/pair?) but clean signal.

[grizzly]

They used those balancing transformers that use CAT5 cable (ethernet) for the actual transmission of the line data.

 

Sorry to be a bit pedantic, but don't assume that Cat5 always equals ethernet. Cat5/5e/6 can be used to carry a wide variety of signals, of which ethernet is but one.

Your basic VGA over Cat5 extenders have nothing to do with ethernet, and there would be serious problems if one was to try and send the signal through an ethernet switch/hub/router etc.

 

Edit: spelling

[kitlane]

Another good source of VGA-Cat5 baluns is www.madnat.com

[stillgoingstrong]

I just spotted in your original post that you mentioned 'a couple of runs'.

 

If you are wanting single source to multiple destinations the AvoCent stuff is really good. The transmitter has 4 outs on CAT5 and each receiver has 1 CAT5 in, CAT5 through and 2 x VGA outputs. They do cost around £200 each but may be more realistic if you have multiple projectors to feed

[harrydir]

Are you referring to CPC part CS10932 (catalogue page 891)? It costs £56.52+VAT per tx/rx pair.

 

Anyone else tried this item?

 

I've used this product in a few different places at work, and when it works it's great, however it seems susceptible to noise on the mains supply (e.g. nearby fluorescent light switching on/off) which causes the picture to go purple, and has to be rebooted to reset it. We have three sets of them and it seems to affect all of them...

 

Just to second this exact problem - most of the time they are fine, but on some installs they just aren't happy and turn purple with the slightest fluctuation in power supply, only solved by a reset of the affected end (tx or rx). I often work in the same hall using the same ethernet direct patch with a box on each end and 20% of the time they don't work. I've since bought expensive ones.

[Thegael]

Hi

I would personally go for 5 core RGBHV cable. When you do the run for cables, add a couple of CAT5e or CAT6 cables as well, and perhaps even a RG59 for video signal, just in case. Also if the projector has a socket for wired remote (usually a 3.5mm jack) run a cable for that as well. All these extra cables seem a bit like overkill, but are cheap enough, and provide an easy upgrade path should you want to. I would also suggest getting a signal processor at the beginning of your run. We use the Extron 203 RXI or 203 VTG. These are grey box that switches between two or three inputs, amplifies the signal and has RGBHV outputs. The one with the VTG suffix has a built in video test generator, that outputs test signals at different resolutions. They also allow you to resize the image with some dials to fit it horizontally and vertically.

There are also other brands that do a similar thing (Kramer, Analog Way) but I prefer the Extron. Usually they can also be found second hand on eBay.

 

Glenn

[mac.calder]

Hi

I would personally go for 5 core RGBHV cable. When you do the run for cables, add a couple of CAT5e or CAT6 cables as well, an5d perhaps even a RG59 for video signal, just in case. Also if the projector has a socket for wired remote (usually a 3.5mm jack) run a cable for that as well.

 

Wired remote with a 3.5mm jack is often labeled Control-S.

 

I second the use of a video interface (another vote for the Extron 203 VTG - the VTG alone is great for when you are setting up the room, and are waiting for the client to supply their laptop - allows them to walk in and see SOMETHING on the screen (and allows you to focus if need be)) and 5 BNC.

 

One of the rooms at work has no cat5 patching, and using BNC+203, we often have runs greater than a hundred meters (after the signal goes back to the patch bay, then to the projector) - the image is crisp and clear.

 

We also use magenta video over cat5 all the time (it's what we use everywhere else), and whilst the images are not quite as crisp as BNC, it is a lot more convenient.