Spec'ing out new cabling - need recommendations

Conversations around originating a webcast for conference, including cameras and mixers.
aclawson
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Spec'ing out new cabling - need recommendations

Postby aclawson » Sun May 15, 2011 7:00 pm

The wiring in our stake center is deteriorating and obsolete. The coax used to distribute video within the building (chapel, gymnasium plus multiple overflow rooms) has some runs that provide poor video signals at best and considering that modern digital projectors don't have coax inputs require a modulator (we currently use old VCRs) which introduce unnecessary points of failure and unnecessary complexity the time has come to modernize.

I am putting together a suggested plan of attack for wiring improvements and would greatly appreciate any input - especially from people who have gone through this before.

The building is one story (with a small 2nd level section above one foyer) about 250' long and 150' wide with a large open courtyard (dead space) offset from the center of the building. The plenum has been almost completely filled by a retrofit to forced air ducting several years ago. Electric systems can be expected to be noisy - this is not a clean r/f environment. The building is many decades old and has reinforced masonry throughout. Wireless networks do not have good range in the building.

Voice and data demarc under the steeple with about a 200' run back to the a/v closet where the satellite receiver and audio distribution are parked. From the A/V closet it is about 25' to the stake clerk's office and about 125' to the offices for the two wards that meet in the building (back down the same hallway from the steeple demarc point). The longest run that could conceivably be needed is around 300' for ethernet.

Technologies and available data connections can be expected to change over time, but wiring this building is difficult enough that I'd like to have necessary cable pulled once and suffice for anything that can conceivably come down the pipeline in the future.

The building's audio distribution system will remain untouched.

The no-brainer is running cat 6 (preferably 6a due to all of the noise in the building) to various rooms and offices for internet connectivity - MLS machines, the FHC and for internet streams. The question I have is for replacing the existing coax drops with something modern and doesn't require duct tape to keep intact.

For most of the drops I want to have the cat 6a plus a dedicated video/audio connection. This audio connection should be completely independent from the audio distribution system to provide a backup as well as flexibility.

RCA composite bundles are a little thick and with two runs over 125' I think we'd be pushing the limit on run length.

For (relative) simplicity's sake what if we pulled two runs of 6a to each drop, specifying one for data and one for audio/video. For the moderate-term future the 2nd runs of cat6a for RCA composite connections (I believe you need a balun for this to work?)

Any other suggested ways of working this?

michaelfish
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Postby michaelfish » Sun May 15, 2011 8:57 pm

Baluns are not the ideal solution for every application; certain environments and applications will degrade twisted pair transmission performance. It is crucial that you pre-qualify your application and avoid any potential hazards. Video through high quality RG-59 or RG-6U cable can be run in excess of 400 feet. However, all of the following applies to coax and using baluns over Cat 5/6:
  • Balun performance may be compromised in facilities with excessive RF interference, such as facilities with large AC motors.
  • Twisted pair cabling, such as Cat 6, carrying an audio-visual signal should not be run within one foot of fluorescent lights.
  • Twisted pair cabling, such as Cat 6, carrying an audio-visual signal should not be run for more than three feet parallel to high voltage lines. Ideally, twisted pair cables which must cross high voltage lines should do so at a 90 degree angle.
  • Twisted pair cabling, such as Cat 6, carrying an audio-visual signal should not be passively split. Cat 6 carrying an audio-visual signal may be run through a passive patch bay as long as point-to-point connectivity is maintained.
  • Data, such as computer Ethernet traffic, should not run on the same twisted pair cable as your audio-visual signal.
  • Balun performance may be compromised with excessive jumping and signal conversions. Every time you convert a signal or pass through a connector, there will be some signal loss. Try to maintain a point-to-point connection, or if impossible, use an active product.

russellhltn
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Postby russellhltn » Sun May 15, 2011 9:38 pm

aclawson wrote:The wiring in our stake center is deteriorating and obsolete. The coax used to distribute video within the building (chapel, gymnasium plus multiple overflow rooms) has some runs that provide poor video signals at best and considering that modern digital projectors don't have coax inputs require a modulator (we currently use old VCRs) which introduce unnecessary points of failure and unnecessary complexity the time has come to modernize.


While I do not disagree that the current situation has problems, I think doing anything now is running ahead of any firmly established standards - particularly any standards practiced by the church.

The existing system is supported by the FM group. They oversaw the installation and can call in help as needed to repair it. If you put in something new, it's going to be on you and your successors to maintain it. The FM group can not help beyond running cable.

My personal suggestion is to leave the current system in place and running only what is needed to support routine General and Stake Conferences. Wait and see what the church does (and let them pay for the changes).
Have you searched the Wiki?
Try using a Google search by adding "site:tech.lds.org/wiki" to the search criteria.

michaelfish
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Weak RF signals

Postby michaelfish » Mon May 16, 2011 1:45 am

It may be possible that your degraded RF signal is due to the improper use of RF splitters. That is what we found at our building.

We wanted to use several TV monitors for the choir in the loft, but RF signal was so weak it had to be amplified in order to view a decent signal. We discovered the problem was that RF splitters had been used 4 times along the same line, resulting in a measly 1/64th of the original signal for the choir monitors.

The first was a 4-way splitter on the output of the RF modulator in the video cabinet (1/4 signal to each line). After the long run to the chapel, the next split was to an unused outlet in the floor (1/8th signal), there was another split at the podium (1/16th signal) and then we demolished what little was left when we added a 4-way splitter for our choir loft TV monitors (resulting in 1/64th of the original signal). We solved our problem by removing the splitter for the unused floor jack and used taps at the podium and choir TVs.

In order to keep the power of RF signals balanced along a long cable run, the use of taps instead of splitters can enable you to balance the RF output by tapping off a portion signal for the first TV (7 db is usually sufficient) and pass the remaining signal down the line.

aclawson
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Postby aclawson » Mon May 16, 2011 3:50 am

RussellHltn wrote:While I do not disagree that the current situation has problems, I think doing anything now is running ahead of any firmly established standards - particularly any standards practiced by the church.

The existing system is supported by the FM group. They oversaw the installation and can call in help as needed to repair it. If you put in something new, it's going to be on you and your successors to maintain it. The FM group can not help beyond running cable.

My personal suggestion is to leave the current system in place and running only what is needed to support routine General and Stake Conferences. Wait and see what the church does (and let them pay for the changes).


The stake president asked me to come up with a recommended plan that he can give to the FM group.

The firmly established standards call for cat6 wiring to be installed by the FM group to accommodate meetinghouse internet capabilities - since the video feeds need to go to the same locations it makes sense to recommend the other cabling to be pulled at the same time. During the most recent stake conference (broadcast from SLC) there was a complete failure of the audio distribution system that prompted an emergency workaround involving cheese boxes, extra TVs and the speakers usually used for stake youth dances.

Given that the FM group is going to be pulling wire anyway, that the coax system is not compatible with current established standards (the digital projectors provided by the FM group do not natively support coax) and that it is wise and prudent to have backup plans in place I am asking for suggestions on what we should request and what will make things easier in the future that will not only meet our current needs but also make the eventuality of webcasting possible.

russellhltn
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Postby russellhltn » Mon May 16, 2011 10:35 am

aclawson wrote:The firmly established standards call for cat6 wiring to be installed by the FM group to accommodate meetinghouse internet capabilities


True

aclawson wrote:since the video feeds need to go to the same locations it makes sense to recommend the other cabling to be pulled at the same time.


Logical yes. But I'd still caution against creating a whole new system.

aclawson wrote:During the most recent stake conference (broadcast from SLC) there was a complete failure of the audio distribution system that prompted an emergency workaround involving cheese boxes, extra TVs and the speakers usually used for stake youth dances.


Unfortunate, but any system can fail. This failure is the FM group's problem to fix. As for a backup, I think you found one.

aclawson wrote:that the coax system is not compatible with current established standards


That's the problem. I'm not seeing any new established standards anywhere to replace Closed Circuit TV.


aclawson wrote:(the digital projectors provided by the FM group do not natively support coax)


Let's start there. The projector in my stake has a baseband video input and a VGA input. Looking around, the passive cable limit is around 100' and is susceptible to interference. Composite signal is Standard Definition - yesterday's standard.

Perhaps you've got a newer projector that has HMDI or Component, but a quick Google suggests similar limits for passive cabling. To get beyond that, you're going to need some kind of active box. So you're back to another box next to the projector.

There's also the issue that digital systems could introduce a noticeable delay in the picture. That's OK in isolated locations, but would be a problem when the screen is used in the overflow where the audience can see the live action. If there is a delay, then you have the problem of delaying the audio to maintain lip sync.

And we haven't even touched on the distribution equipment you'll need in the equipment rack.

If you do move forward with this, I'd suggest you mock up the system, including the cable length and make sure this is going to work before you pull any cable in the walls.

Or, you could go with my suggestion and just wire for Internet (with maybe a few extra runs) and wait and see what happens with the church video systems.
Have you searched the Wiki?

Try using a Google search by adding "site:tech.lds.org/wiki" to the search criteria.

StevePoulsen
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Postby StevePoulsen » Mon Jun 13, 2011 3:00 pm

aclawson wrote:Given that the FM group is going to be pulling wire anyway, that the coax system is not compatible with current established standards (the digital projectors provided by the FM group do not natively support coax) and that it is wise and prudent to have backup plans in place I am asking for suggestions on what we should request and what will make things easier in the future that will not only meet our current needs but also make the eventuality of webcasting possible.


RussellHltn wrote:That's the problem. I'm not seeing any new established standards anywhere to replace Closed Circuit TV.

Let's start there. The projector in my stake has a baseband video input and a VGA input. Looking around, the passive cable limit is around 100' and is susceptible to interference. Composite signal is Standard Definition - yesterday's standard.

I wanted to Jump in on this one. I am assuming that buy does not natively support coax, you mean that they don't support RF (TV channels on Coax Cable).
I make this assumption because the standard projectors provided by satellite support to the FM groups don't. However, they do support composite (Baseband, Raw etc) video over coax.
I this is not that case, I would (Kindly) ask the FM manger where they get their projectors from.

If however this is the case and you are pulling new cables, I would recommend having coax cables for base band video pulled from the satellite closet to the needed locations. (This is currently done on new installations and has been for about the last 4 years)
After the cables are pulled you (the FM) will likely need at least 1 additional Video DA to distribute the cables to these locations, at this point, this will allow you to use the standard projectors and other equipment without installing costly digital cable and gear that may or may not ever become standard in church buildings.
Steve Poulsen - Meetinghouse Facilities Technology Engineer


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