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Author Topic: RF Interference fro LED Video walls  (Read 7761 times)

Kevin McDonough

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Re: RF Interference fro LED Video walls
« Reply #10 on: March 23, 2013, 07:56:52 am »

hey

while I'm not enough of an electronics Wiz to know much about the details of what causes the interference or how to prevent it, I do remember reading this article in Lighting & Sound International a while ago that spoke of exactly this issue.

http://edition.pagesuite-professional.co.uk/Launch.aspx?EID=5ef20413-6934-481a-ab19-3aae38bece6d&pnum=63

k
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kristianjohnsen

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Re: RF Interference fro LED Video walls
« Reply #11 on: March 23, 2013, 11:32:56 am »

We were discussing the issue of RF interference from LED walls at work this morning. I'm wondering which part of the wall would generate the problem. Is it the PSU's, the spider web of interconnecting wires within the panels, PCB's? Any insight would be appreciated. Thanks.

At a recent Sennheiser class, I heard that at the last Norwegian-held Eurovision finals there was a vendor who was prototype-testing a new brand of LED-wall.  The radiated noise around the venue was right right up there in RF level with the actual wireless mics and receivers :O  Needless to say, that design was not approved.

I think this is one major issue:  The market (even the pro market)is beeing flooded with surprisingly cheap LED apparatus.  I'm not surprised that some manufacturers cut some corners...
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Bob Charest

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Re: RF Interference fro LED Video walls
« Reply #12 on: March 23, 2013, 05:19:49 pm »

hey

while I'm not enough of an electronics Wiz to know much about the details of what causes the interference or how to prevent it, I do remember reading this article in Lighting & Sound International a while ago that spoke of exactly this issue.

http://edition.pagesuite-professional.co.uk/Launch.aspx?EID=5ef20413-6934-481a-ab19-3aae38bece6d&pnum=63
Thanks for posting the article, Kevin!
k
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Henry Cohen

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Re: RF Interference fro LED Video walls
« Reply #13 on: March 27, 2013, 07:39:20 am »

In the older LED designs, especially the earlier analog products, it was the power supplies that were the primary broadband noise generator. Secondarily was the LED drivers themselves.

With first generation of digital LED modules, the biggest emitter of RFI was no longer the PSU, but rather the scalers and the interconnect cables. Digital data is noisy and the cables between the scalers and modules, and between modules, was generally unshielded. This remains the primary RFI source of noisy walls.

The better products are using shielded interconnect cabling, and better shielding of scalers and the rear of the LED module assemblies themselves. The e-Galaxy Winvison series and the new Daktronics seem to be rather quiet. I've been seeing only 6db increase in the noise floor from about 300MHz to 1GHz at 3 feet on average with no harsh spurs.
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Henry Cohen

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Henry Cohen

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Re: RF Interference fro LED Video walls
« Reply #14 on: March 27, 2013, 07:43:04 am »

As an employee of Daktronics I know all of our products go through our EMI chamber for extensive testing. What they are tested to I have no idea.  See attached pic.

This is a fundamental error in RF emissions measurement: Only one module is being measured, rather than a large assembled wall with multiple modules, interconnect cables and support electronics. The RF emissions do not scale linearly as more components are added.
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Henry Cohen

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David Sturzenbecher

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Re: RF Interference fro LED Video walls
« Reply #15 on: March 27, 2013, 09:24:29 am »

This is a fundamental error in RF emissions measurement: Only one module is being measured, rather than a large assembled wall with multiple modules, interconnect cables and support electronics. The RF emissions do not scale linearly as more components are added.

Henry, the picture I attached was actually testing of audio components in prep for ETL certification, not LED display modules.  We test all components... modules, power supplies, etc and full displays.  I was simply posting the picture to show our chamber.

   
« Last Edit: March 27, 2013, 10:37:56 am by David Sturzenbecher »
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Re: RF Interference fro LED Video walls
« Reply #15 on: March 27, 2013, 09:24:29 am »


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