HD-SDI cable?

[Matthew Rogers]

Hey guys, I've been told in the past and also this week by my buddy that you need a certain kind of BNC cable to run SDI/HD-SDI over. However, I've never had any trouble with running SDI over decently flexible cable--I've never tried the super flexible cable though.

Does anyone know what the min cable specs needed for running HD-SDI from the RED to a monitor?

Matthew

 

[Shawn Nelson]

75 ohm

 

[Mitch Gross]

At least 3Ghz signal passthru, 4.5Ghz even better. Don't think that all BNC cables deliver this spec -- they do not.

 

[Anders Yarbrough]

The basic jist of it, that I've found in practice, has been:
o What Shawn said is pretty much it: 75 Ohm
o You can run the flexible stuff that doesn't have the passthru that Mitch is talking about, but you will get a shorter run.
o If you run the higher end solid conductor coax, that has the passthru that Mitch is talking about, you should be able to get a much further run without getting sparklies. Don't quote this, but maybe 100'

 

[david farland]

Nice to know thats guys.

The other related item is HDMI/DVI cables, which I guessing has far less protection from interference and produces 'noise' at less runs than SDI cables.

I'm guessing that 5~10M gets into the noise susceptable range for HDMI/DVI cables.......depending on the emf (apologies) environment.

I've compared.....

1) HDMI output on a Dell 24".
2) SDI (preview) output with BLACKMAGIC SDI/DVI converter on another Dell 24".
3) AJA SDI/Component converter to a Sony PVM D20L5.

Not much difference in the 'basic' picture quality.

My philosophy would be use the HDMI for shorter 5-7M runs and the SDI solutions for longer....or if I get interference on the HDMI solution.

Obviously if I have a SDI monitor, the preference would be to use SDI cables/outputs.

Dave,

 

[Michael Bravin]

Almost any cable with BNC connectors on each end will pass HDSDI. The issue is at what distance. The good news is that when the cable cannot pass enough signal it (the signal) goes away. No static drop outs etc just nothing, it's called the cliff effect. The better the spec of the cable the longer the run. Proper cable will run HDSDI over 1000 feet. The reason to use good cable and connectors is to insure success, there is no picture quality improvement with better cable or connectors, just better and more reliable performance.

Michael Bravin
Chief Technology Officer
Band Pro Film & Digital

 

[Matthew Rogers]

Almost any cable with BNC connectors on each end will pass HDSDI. The issue is at what distance. The good news is that when the cable cannot pass enough signal it (the signal) goes away. No static drop outs etc just nothing, it's called the cliff effect. The better the spec of the cable the longer the run. Proper cable will run HDSDI over 1000 feet. The reason to use good cable and connectors is to insure success, there is no picture quality improvement with better cable or connectors, just better and more reliable performance.

Well, I am only wanting a 25ft and 50ft run so I am in good shape.

Matthew

 

[Mitch Gross]

Good to see you here Michael. The only other problem with non-compliant cable is backfeed. If it does not properly pass the signal, a voltage buildup can occur and backfeed into the camera, resulting in a short. This used to be a product on the Varicam, which could lead on that camera to a $2000 board level replacement. Ouch.

If a non-compliant 25' BNC cost $15, then a compliant one costs maybe $25. Do yourself a favor and get one that is compliant. Even the little adaptor cables RED supplies to go from mini-BNC to standard size are compliant.

 

[Matthew Rogers]

Good to see you here Michael. The only other problem with non-compliant cable is backfeed. If it does not properly pass the signal, a voltage buildup can occur and backfeed into the camera, resulting in a short. This used to be a product on the Varicam, which could lead on that camera to a $2000 board level replacement. Ouch.

If a non-compliant 25' BNC cost $15, then a compliant one costs maybe $25. Do yourself a favor and get one that is compliant. Even the little adaptor cables RED supplies to go from mini-BNC to standard size are compliant.

So how do you tell what is a compliant cable? Are you talking about the 50/75 ohms or what?

Matthew

 

[Mitch Gross]

They are sold as (and the cable jacket marked as) 3Ghz up to 4.5Ghz and generally called HD-SDI compliant. We sell these but so do plenty of other places. Try Comprehensive or Markertek.

 

[Harry Clark]

I use the Markertek assembled Canare cable. L-61S I think? Never had trouble.
Cheers,
Harry