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Topic: Snow showing up on projector randomly during service
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Joined: Jun 17, 2014
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Hey all,
I am in a mobile church environment where I run multiple video signals around 100-130 feet to different items (one projector, one TV for conference monitor for worship, and one to a laptop for livestreaming). I am using a macbook pro laptop loaded with ProPresenter 5.

The signal chain for the projector is display out to DVI adapter -> DVI to HDMI adapter -> Gefen brand HDMI over Cat5 extender -> HDMI cable -> projector.

Now I've gotten random snow showing up every once in a while on the screen during rehearsals, and it would go away on its own after a few seconds, except for this last Sunday, where it "snowed" during video announcements. After disconnecting and reconnecting the HDMI cable running into the projector, it worked normally for about five or six minutes until it "snowed" again, and disconnecting and reconnecting the HDMI cable did nothing.

The ethernet cable we are using is UTP cat6 568A terminated, I don't have the actual cable on me unfortuantely so I can't give the exact specs of it. I've been reading online and seen that it could be a weak signal issue, but these extenders are designed to throw a signal 330ft, so I'm not sure if that is the issue. I know I am supposed to use STP ethernet for the setup, but it's what the company the church hired to put together an AV package gave us.

The outputting end of the extender is slightly off of the ground normally (not good I know). I have also tested all of the HDMI cables, the ethernet cables, and the display to DVI adapter and they all are functioning normally (no random shorts).

Main question: what would you think is causing this problem? This is a major concern to my pastoral staff, and I really want to get this problem solved as soon as possible.

Also, anyone know a good place to get Cat5/6 STP 568 terminated patch cabling that's prebuilt??? My old ones are starting to kink really badly and they're solid core so I am really worried about a nightmare scenario where all the cables break at once.

Thanks so much guys!
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Joined: Mar 28, 2005
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What is the exact make/model of the Gefen extenders? Are they HDBT (HDBaseT) or something else? The only properly reliable way to send HDMI signals is by using HDBT at this point. There are a number of other attempts to do this using other technologies but none have proven to be anywhere near as reliable as HDBT and it has become a nearly universal standard for quality at this point.

Fiber is one of the most reliable point to point connections that is available, but even this typically uses HDBT as the conversion mechanism.

For CAT-6STP patch cables you can pick them up at www.monoprice.com for a really low price as you need them.

Make sure that you are using short HDMI interconnects between your connection points.

I'm not sure the Mac is introducing any sort of issue into the setup, but Macs are notorious for being as incompatible with established standards as they can possibly be. I would do some testing with a laptop with a native HDMI output to see if that presents any issues in the current setup.

The current cable should be reterminated to the 568-B standard as this is most often the requested standard to be used with extenders. As well, if it is 'normal' to disconnect and reconnect the cat cabling, then it must be done extremely carefully so as not to damage the connector. Cat connections were designed for limited use, and HDBT is extremely susceptible to errors, even if a cable tests out properly, it may not work with HDBT or extenders.

I'm thinking when you keep saying display to DVI adapter, you really mean DisplayPort to DVI, more likely mini-DisplayPort to DVI, and I would recommend a quality Mini-DisplayPort to HDMI adapter instead if the final goal is HDMI.

The more connection points you have, the more chance for signal degradation and loss there is.
AV Integrated - Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.
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Here is the exact model of the Gefen converter we use: http://www.gefen.com/kvm/ext-hdmi1.3-cat5-elr.jsp?prod_id=8961


So it wouldn't matter if its built to either an A or B standard, as long as it is terminated at both ends the same way?

I'm using 6ft HDMI cables (not what I would've wanted, but I came on after the order was placed). I'm the one removing the cat6 cable, and I feel like I'm being careful in removing the cables.

With the adapter you mention, yes that is what I am using, I'm a PC guy not a Mac guy so I couldn't remember the name of their video output off the top of my head. And yes I think I'm going to invest in that adapter instead of doing the DVI route, like I said it was given to me that way but definitely would be better to cut out the extra steps.

Just curious, if I cable is marked with IEEE568B, would that make it a "crossover" cable, or how would that work? I ordered some cables that say that and they do not work with any of my extenders (which is a whole other ball of wax but I can tackle that one on my own pretty easily).

Thank you so much for replying quickly, I appreciate the help!

PS I'm testing the extenders right now at my home, and so far I have not seen the "snow" mentioned.
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The extenders are HDBT, which is the best you can get at this point.

The most suspect thing is the cat cabling between the transmitter/receiver units.

The CABLE is cat6. If it is in a noisy environment, it may need to be changed out to cat6 STP, which is a shielded cable.

The manual clearly states that 568B terminations should be used.

http://www.gefen.com/pdf/EXT-HDMI1.3-CAT5-ELR.pdf

Page 8 and page 11 discuss this.

So, that could be causing the issue. You want both ends of the cat-6 cable to be terminated as 568B as shown. If you have a 568A to 568B network cable, that won't work. Both ends must be the same.

You can pick up some really short HDMI cables for not a lot of cash here:

http://www.parts-express.com/Search.aspx?keyword=wired%20hom%20super%20slim%20hdmi%20cable&sitesearch=true

The Wired Home brand is great and really inexpensive.

Certainly worth having some spare cables around at the proper length, but most of my focus for your issues would be in the cat cable's terminations.
AV Integrated - Theater, whole house audio, and technology consultation during the build and installation process in the Washington, DC metropolitan area.