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HD compatible connections

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#1 Iain Baird

Iain Baird

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Posted 17 March 2009 - 08:48 PM

I'm not trying to start a brand bashing thread here but I would like some clarification on a few things when it comes to an HD-SDI signal through the post.

I was under the understanding that an HD-SDI signal will not pass through a regular LEMO plug as the shield is broken at each connection and this causes signal problems. It was because of this understanding that I sourced out a LEMO that had co-ax connections built in so I could upgrade my sled to carry HD-SDI down the post without ever breaking the shield. I can't speak to any interference problems I might encounter with HD transmitters (mentioned in another thread) but I can say that the connection I built works. I've tested it on a scope with an HD tech at Panavision and the Signal through the post was solid.

I know of one company that makes what is advertised as an HD-SDI compatible sled that uses the old style LEMO connections. I've never used it so can't speak one way or another of whether it works properly or not. But based on previous threads about the Ultra 2 and other HD compatible sleds the regular LEMO plugs don't work.

I would like to hear any experts chime in as to what is required to carry a clean HD-SDI signal from point A-B. Does the shield need to remain intact? Or any other variables that might make a difference.

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#2 Jess Haas SOC

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Posted 17 March 2009 - 09:43 PM

With the old style lemo the shield is electrically connected but since its not going through a connector designed for carrying RF the impedance is going to be wrong which is going to result in signal losses. There may also be shielding issues resulting in it being more susceptible to interference.

SD composite signals aren't all that picky about such things especially with the short distance of travel found in a sled. It would seem the HDSDI signal is much pickier and degrades much quicker requiring correctly speced connectors and cable. It would not surprise me if someone was able to get a signal through a traditional lemo.

In the end it all comes down to what works, but if you are not using correctly speced parts you are going to have a weaker signal which will be much more susceptible to things like interference.

~Jess "Not an expert but I do own atleast 3 books on the subject of RF. I have no idea where they are."
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#3 Iain Baird

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Posted 18 March 2009 - 07:06 PM

I wonder if Jerry or anyone from Tiffen can comment on any testing that was done in putting the ULTRA 2 together? I seem to recall previous posts commenting on the inadequacies of a regular LEMO for HD-SDI.
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