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Author Topic: Video VGA over Cat5e cable  (Read 4739 times)

Russ Buck

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Video VGA over Cat5e cable
« on: October 14, 2008, 10:30:55 AM »

We are looking to send our video signal from the main sanctuary computer to a 50 monitor in a overflow room.  it would be about 150' away.  I am leaning toward these VGA over cat5e cable things and was wonder what every experience with them was?  Also in the feature we will be moving are sanctuary projector and mounting it somewhere father away from the computer where we may want to use one of these (cat5e extender things) again.  so I am think about getting one that has multi ports on the base unit so you can use it with more than one receiver.  The one issue is it is more expensive to get one of the multi port units then two single units.  Any input ?

Russ

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Bethel A/G church
Sycamore, IL

Brad Weber

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Re: Video VGA over Cat5e cable
« Reply #1 on: October 14, 2008, 12:53:46 PM »

The general topic has been discussed numerous times in the past, a search to find some of those discussions.

Just like everything else, there is a range of quality and price for video over twisted pair products.  There are a limited number of manufacturers that offer significant training and support and a large number of manufacturers that sell based on price.  I prefer to stay with industry leaders like Magenta Research, Extron and FSR, but many people seem to use less expensive alternatives with satisfactory results.

The multiport transmitters and 'hubs' essentially serve the same function as a distribution amplifier in video, you can either DA the video signal to multiple transmitters or DA the UTP/CAT signal from one transmitter.  Either approach works.  Using the multiport transmitter or a distribution hub may be more expensive initially for the one display but will probably cost less if you run to multiple displays in the future.
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Brad Weber
muse Audio Video
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Re: Video VGA over Cat5e cable
« Reply #2 on: October 14, 2008, 12:55:13 PM »

There are many people on this forum who sing the praises of CATV VGA baluns. I am not one of them. I got burnt once when they were first introduced and have been very leery of them ever since. I have been assured by many of my suppliers that they have been fixed and im sure they have but I still have yet to try again. Im sure I will soon though. OK so al that being said I prefer RGBHV (5 pair mini coax) with converters on each end. I have successfully used this up to 400' with no issues ( I have never needed to go further) You pull the raw cable and then terminate it with the "Proper" tool and connectors. I terminate with BNC and then adapt it to VGA. There are companies that make HD15 connectors that can be terminated using only a small screwdriver that may be an option for you as well. I have never used them but if someone has had good luck with them I would like to know too!
T
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Russ Buck

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Re: Video VGA over Cat5e cable
« Reply #3 on: October 14, 2008, 05:46:55 PM »

So do you use the mini coax with out a booster ?  The tv set has BNC connectors on it..
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Bethel A/G church
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Brad Weber

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Re: Video VGA over Cat5e cable
« Reply #4 on: October 14, 2008, 07:15:23 PM »

Russ Buck wrote on Tue, 14 October 2008 17:46

So do you use the mini coax...

There's the catch.  I am also a fan of RGBHV but you have to address what cable is involved, different cables have different losses.  And with both RGBHV and CAT5 systems you have to consider the signal, higher resolution signals equals greater bandwidth which equates to less distance with acceptable losses.  To accommodate higher resolutions I typically specify that any runs much over 100' use full size RG-59 bundled cable rather than bundled mini-coax, that is based on looking at the bandwidth and expected cable losses involved as well as practical experience.  You can go much further with lower resolution signals but then you may be stuck if you ever try to run higher res signals.

I always recommend the 5 wire to HD15 adapters where you need to connect RGBHV to a VGA connector.  And don't forget that DVI-A and DVI-I also include analog RGBHV.
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Brad Weber
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Joseph White

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Re: Video VGA over Cat5e cable
« Reply #5 on: October 18, 2008, 03:24:11 PM »

I have used Kramer products with much luck. Once you have the signal in a UTP form (unshielded twisted pair, i.e. CAT5) you can run through an inexpensive DA and get several outputs. Whatever you use just stick to the same brand for everything and make sure it has the features you are going to need for your future application.

On a side note. I would consider using DVI instead of VGA. VGA has limited capacity and if you ever want to consider going to a higher quality than XVGA it will be much easier to do with DVI. It is a little more expensive, but it would be cheaper to do it now than replace your whole distribution system later.
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Joseph White
Calvary Chapel Melbourne
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Brad Weber

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Re: Video VGA over Cat5e cable
« Reply #6 on: October 19, 2008, 09:02:51 AM »

Joseph White wrote on Sat, 18 October 2008 15:24

On a side note. I would consider using DVI instead of VGA. VGA has limited capacity and if you ever want to consider going to a higher quality than XVGA it will be much easier to do with DVI.

This happens all the time.  What about DVI-A, which is "DVI" but also is RGBHV?  Do you really mean "VGA" as in the 640x480 graphics standard or "VGA" as in an HD15 connector that carries RGBHV signals?  If you are talking about VGA as the the physical connector, what makes that have a "limited capacity" and DVI "higher quality"?

Since is simply a signal path and not an interface standard, RGBHV has essentially unlimited bandwidth, the bandwidth that it can transmit is limited only by the line losses.  DVI, both DVI-A and DVI-D, is an interface standard and there are specific limitations defined as part of the standard.

There are situations where there may be advantages to DVI-D in how it affects the display device or not needing to worry about skew in UTP transmissions, but there can also be issues with HDCP and DDC, especially when sending the signal to more than one display.  DVI and HDMI are really intended to be a source to single display connection and routing or distribution can have problems if not handled properly, for example the source may see that DDC data for the first device and base the signal sent on that, which may not be a signal the other devices accept.

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Brad Weber
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Arnold B. Krueger

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Re: Video VGA over Cat5e cable
« Reply #7 on: October 19, 2008, 09:51:23 PM »

Brad Weber wrote on Sun, 19 October 2008 14:02



What about DVI-A, which is "DVI" but also is RGBHV?




Let's see if reading the acronym can help us with this question.

DVI-A = Digital Video Interface Analog.


Is it digital or analog or what? When people see DVI they expect that the D stands for digital and the primary goal is digital transmission of video data.

Obviously, DVI-A is simply a retrograde compatibility mode. DVI-A is not really what people are thinking of when they ask about comparing DVI to VGA.

Quote:


Do you really mean "VGA" as in the 640x480 graphics standard or "VGA" as in an HD15 connector that carries RGBHV signals?  If you are talking about VGA as the the physical connector, what makes that have a "limited capacity" and DVI "higher quality"?

Since is simply a signal path and not an interface standard, RGBHV has essentially unlimited bandwidth, the bandwidth that it can transmit is limited only by the line losses.



Additionally, there are significant limitations in both the transmitters and the receivers. The losses in the wiring are especially vexing because they are different even within various parts of the same installation, and can never be completely compensated for.

Quote:


DVI, both DVI-A and DVI-D, is an interface standard and there are specific limitations defined as part of the standard.



Here are three possibly relevant advantages to digital interfaces as compared to analog interfaces:

(1) Analog interfaces cannot ever be perfect. They always have some loss. Digital interfaces are perfect within their defined capabilities. When cable lengths are like a meter, the losses in an analog cable are generally trivial. But in churches, we very often end up with cables that are 100 or more feet long. Clearly visible losses are common, and must be compensated for by manual adjustments at the transmitting and/or receiving end.

[2] If the data is already digital, and the output device converts the data to digital in order to output it, then using a digital interface will avoid an unnecessary conversion from digital to analog and back to digital again. This benefit is obvious even when doing something as simple as connecting a monitor to a PC with a 1 meter cable. DVI-D or DVI-I invariable looks better than the usual 15 pin analog connection.

[3] The basic nature of analog data is imprecise. Small variations in amplitude and timing can affect important things like the image size, centering, and color fidelity. Digital data is inherently precise. If there are minor changes in timing and amplitude of a digital signal, they can and generally are automaticaly and precisely removed by the receiver. You generally get either the best picture possible, or in the case of a system failure or error, you get no picture at all.

Quote:


There are situations where there may be advantages to DVI-D in how it affects the display device or not needing to worry about skew in UTP transmissions,



Also true, but what about the three *major* advantages above? Are they so trivial  and uncommon that it is appropriate to omit them?


Quote:


but there can also be issues with HDCP and DDC, especially when sending the signal to more than one display.  DVI and HDMI are really intended to be a source to single display connection and routing or distribution can have problems if not handled properly, for example the source may see that DDC data for the first device and base the signal sent on that, which may not be a signal the other devices accept.



Also true, but this presumes that the various displays have different resolutions.  I have a number of applications for multiple displays driven by a splitter in mind, but they would always have the same resolution, and/or the resolution would be manually be set at the source.


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Re: Video VGA over Cat5e cable
« Reply #7 on: October 19, 2008, 09:51:23 PM »


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