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Author Topic: Video signal strength!!  (Read 699 times)

Barry Dunlap

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Video signal strength!!
« on: October 16, 2018, 07:22:40 pm »

I have a Mac Pro (Mid 2012)
Processor 2x3.06 GHz 6-Core Intel
Memory. 64 GB. DDr3
Graphics. ATI Radeon HD 5770 1024 MB

We use this system at the church and run an overhead projector and three TV monitors from it. The overhead picture is perfect and operates flawless. However the three TV's are another story. Two of the TV's are in the foyer about 15 feet from the computer and the other is on the back wall of the sanctuary about 15 ft from the computer. Some days the two in the foyer are clear as a bell and on other days they are so jumpy and blurry we have to turn them off. The one on the back wall will seldom work. When it does it is in black and white and never color. It usually says on a few minutes and then begins floating a warning that there is no signal.

How can I boost the signal to these three TV monitors? They are all three being connected with coax TV cable. I now of churches that run multiple TV monitors throughout the building and don't seem to have a problem. What am I doing wrong? Or what do I need to do to make the connections more usable?

Thanks for your help!!
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Mike Caldwell

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Re: Video signal strength!!
« Reply #1 on: October 16, 2018, 08:00:47 pm »

What kind of video signal are you sending to the TV's using the coax cable?
It could be RF in one form or another, HD-SDI, composite video.

On the TV's what input do you select to get a picture.

Ken Webster

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Re: Video signal strength!!
« Reply #2 on: October 16, 2018, 09:14:17 pm »

Also, how is your cabling arranged?  Many devices are constructed with coax in and out so it is tempting to daisy chain them together but this is bad for signal integrity.  It is better to use a splitter or splitter/amp or distribution box near source and run a separate cable to each device.

Also, some coax plugs and sockets are very poorly designed.  I have one that has a spring sleave between the plug and socket shield shells.  This is intended to keep things tight but it means you have more contact surfaces and is just trouble.  Video is pretty sensitive to connection issues between cable and plug and plug and socket.  It would be helpful to measure cabling impedance/resistance but better to meter the signal strength at the cabling connection points if you have the means.

Ken
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Barry Dunlap

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Re: Video signal strength!!
« Reply #3 on: October 17, 2018, 09:47:41 am »

Thanks for the replies!   I am uncertain as to what kind of video signal is being sent to the TV's.  On the TV's I believe that the input selection is video1 on each.

As for the cabling arrangement it is as follows:  coming from the computer video card it goes into a multiplexer unit.  From there the signal to the overhead projector is VGA and to the TV's it is a RCA cable that goes to a converter changing it to coax. From there it is split in two.  One to the TV on the back wall and the other to the foyer area.  In the foyer area it goes into one TV via coax and then out to the second tv in same manner.  The two tv's are mounted on the ceiling back to back.

I have tried various kinds of coax connectors including gold ones, etc but same results each time.

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Caleb Dueck

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Re: Video signal strength!!
« Reply #4 on: October 17, 2018, 01:13:26 pm »

Make and model of every device?

Sent from my VS980 4G using Tapatalk

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Taylor Hall

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Re: Video signal strength!!
« Reply #5 on: October 17, 2018, 02:01:00 pm »

It sounds like all the "converting" is causing signal degradation/desync for sure. I'll also echo Caleb's request for the model of converters and multiplexer you're using as there could be a setting that would help you out.

Either the RCA-Coax converter isn't outputting a clean enough signal to the TVs, or the diplexer you're using to split the coax signal to each TV is adding too much attenuation. You said you tried using different ones, did any of those happen to be active (powered)? The coax signal could just need a little boost.

Ideally, having as few converters in the chain will make your system much more reliable and easy to diagnose should something go wrong. Swapping that all out for something that works over cat5 (like a balun or HDBaseT system) to each device would work great, too, but probably outside of the budget (assuming there is one :P).
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Andy Deglado

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Re: Video signal strength!!
« Reply #6 on: October 17, 2018, 05:06:51 pm »

I have a Mac Pro (Mid 2012)
Processor 2x3.06 GHz 6-Core Intel
Memory. 64 GB. DDr3
Graphics. ATI Radeon HD 5770 1024 MB

We use this system at the church and run an overhead projector and three TV monitors from it. The overhead picture is perfect and operates flawless. However the three TV's are another story. Two of the TV's are in the foyer about 15 feet from the computer and the other is on the back wall of the sanctuary about 15 ft from the computer. Some days the two in the foyer are clear as a bell and on other days they are so jumpy and blurry we have to turn them off. The one on the back wall will seldom work. When it does it is in black and white and never color. It usually says on a few minutes and then begins floating a warning that there is no signal.

How can I boost the signal to these three TV monitors? They are all three being connected with coax TV cable. I now of churches that run multiple TV monitors throughout the building and don't seem to have a problem. What am I doing wrong? Or what do I need to do to make the connections more usable?

Thanks for your help!!
If you want to get the best signal to your TV's I'd switch to HDMI. We have done this at out church and have monitors and projectors all over the place. If the run is longer than 20 ft, you will probably want to use HDMI over Cat 6 (4 of our runs are well over 100 ft).

Sent from my SM-G965U using Tapatalk

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Ken Webster

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Re: Video signal strength!!
« Reply #7 on: October 17, 2018, 08:16:12 pm »

and to the TV's it is a RCA cable that goes to a converter changing it to coax.

Is the converter a powered device or just a RCA to coax in line plug?

Ken
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Mike Caldwell

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Re: Video signal strength!!
« Reply #8 on: October 18, 2018, 01:03:16 am »

I'm thinking good ole composite video is what your using. If that's the case you can not really just split the signal with a T connector and send it into terminating inputs like would be on the TV. You may still have other issues but if your sending composite video to the TV's need an active video distribution amp.

Are the cables plugged into the yellow video connectors on the TV's.



Ken Webster

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Re: Video signal strength!!
« Reply #9 on: October 18, 2018, 01:26:13 am »

OK, I am going to assume that the TV is receiving a composite video signal because this is consistent with selecting the video 1 input on the TV.  That means, you have a composite video signal from the multiplexer RCA out and are using a passive in line converter plug to connect the RCA cable to a 75 ohm splitter and coax cable that feeds the same composite video signal to the TVs.  The use of 75 ohm coax is not a bad thing and has probably been done because of the distances involved.  Now there are just a few points and some suggested options for you.
1. It would be best to follow a previous suggestion to use separate HDMI feeds to each of the TVs and probably the projector as well.  This is more capable of transmitting cleaner digital HD over longer distances and can carry imbedded digital audio as well.  This would allow the TVs to handle in synch audio which is more convenient than supporting a separate, audio distribution system (maybe you donít but could).  However, this will probably require replacing a lot of gear which you may not wish to do right now.
2. Splitting the signal reduces its power so, it would be better if the multiplexer had 3 composite video outputs and you used a separate cable to feed this signal to each TV.  That way each TV gets the maximum available signal strength.  May require a multiplexer upgrade and more cabling.
3. Have you got enough signal strength to feed 1, 2 or 3 TVs?  As a test, you could try removing the splitter and driving only one TV.  If that works, try the splitter again but disconnect the video cable that feeds the 3rd (daisy chained) TV.  If that works, then you know you have enough power for 2 TVs on the one multiplexer output but not 3.  However, any use of a splitters will reduce signal power and the quality and reliability may suffer noticeably.  If resources are tight, it may be worth a try pending a better solution.
4.  Looking at the setup, it seems to me that it was probably set up properly for the time it was done. Though I suspect it may have initially only driven 2 TVs and the 3rd may be a later add on.  If that is the case, then I suspect that your cabling terminations and plugs have degraded over time.  The fact that it performs inconsistently tends to support this probability.  You could try re-terminating the cables with new or cleaned up plugs.  Deoxit does a good cleaning and conditioning kit.  It takes some effort though and donít forget to tighten up the plugs and sockets.
5. It is definitely not good to daisy chain a TV off another oneís video out. A splitter is better but separate multiplexer outputs and cables is the best way to go as there is no signal power loss that way.

I typed this while Mike replied. I agree that you could drive what you have with an active video distribution amp, but I think a multiple output multiplexer would achieve similar results with fewer connections in each TVs signal path.  It's an opinion anyway.

Ken
« Last Edit: October 24, 2018, 07:48:12 pm by Ken Webster »
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