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HD cable interference


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#1 JensSchroeder

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Posted 23 April 2013 - 02:18 AM

Hi All,

 

I have had a strange problem with my internal HD cable. When I plugged in the HD signal from the camera to my internal HD-cable of the sled, the sound department in the TV studio had massive interference noise on their public address system speakers in the UHF-range. Then I connected Camera directly with my monitor on no more problems. Anyone had the same problems or any idea?

 

Thanks in advance. Cheers,

 

jens


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#2 Tuomas Viitakoski

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Posted 23 April 2013 - 03:45 AM

Hi Jens,

First of all..
:ph34r:
..as long as your video is fine you dont say a thing..

Then more serious:
The post cable (like basicly any cable) works as an antenna. 
How good antenna? - depends on their shielding. It's absolutely possible to have interference in your video feed from all the waves blasting through your sled. Sometimes just a walkie-talkie can mess up your video.

PAL/NTSC-post cables were more prone to this kind of interference but HD-SDI/3G/6G etc have more shielding materials (like foil) and that's why they are thick as garden hose.
The video line outside of the post could have been just different type of cable with different specs and therefore not affecting so much.
Hopefully someone can give you a more thorough answer.

Just for the record - what type of sled & post cable you got?


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#3 Evrim KAYA

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Posted 23 April 2013 - 04:10 AM

:ph34r: ..as long as your video is fine you dont say a thing..
 

 

hahaha! good one Tuomas!

 

 

I never thought that hd-sdi cable could cause this mush interference to outside world. Generally it’s the other way around; the unshielded bnc getting interference from outside world preventing it from cleanly carrying the sdi signal.

Could you also tell us what kind of camera you are using? It could be relevant as the signal is created by the camera in the first place.


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#4 Jens Piotrowski SOC

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Posted 23 April 2013 - 08:41 AM

Hi Jens,

 

sounds like a "leak" in your system. The HD-SDI signal is essiantially an RF signal and it looks like your internal wiring is leaking or radiating, like an antenna. Check with Markus (Bear-Bel) or Christian Betz (Betz-Tools) in Munich. Curt @ Artemis in Munich might be able to help too.

 

Gruesse!


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#5 Jameson Johnson

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Posted 23 April 2013 - 12:11 PM

HDSDI is actually a voltage carried over the cable, not an RF signal as described, though it would be possible for other high powered transmitters nearby to introduce voltage into the cable and cause interference in your picture. However, that's not what was described. 

 

If the sound department is getting interference from you when you plug in, then it's not an issue of your gear receiving RF interference, but them getting it from you. But this is an odd situation given that your HDSDI monitor cable shouldn't have anything to do with their wireless transmitters.

 

You mentioned you were in a TV studio - are you using a studio camera and tethered to their system or wireless? Which camera is it? What else is on your sled? Do you have any transmitters of any kind? Does sound have any devices on your rig?

 

This one has be intrigued, so at the very least I'm curious what the solution is, but I'd love to help troubleshoot.


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#6 JensSchroeder

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Posted 23 April 2013 - 02:05 PM

Hi guys,

 

first of all thanks for your comments and thoughts. I just can repeat it, I love the steadicam forum.

 

As for my strange problem - Tuomas, I unfortunately couldn't hide it because we were in the process of rigging down the camera for a wired one. And then the focus puller noticed that,  when I plugged out my bnc cable , all of a sudden the interferences were gone. With nobody else around I probably would have plugged in directly to the monitor and have said, I did a very complicated repair and now everything is fine ;-)

 

I used a wireless camcorder from Ikegami (first time for me), had the BFD for focus and my sled is the new carbon sled 

from Baer.Bel. I wasn't connected in any kind with the sound department, no microphone on the camera, no sound transmitter attached. Being an antenna with my sled would be kind of logical to me, but this time it seems I had an sled that had become a transmitter. Plus my position in the studio wasn't very close to the sound department.

 

I'll let you know when I have found out something.

 

Fly safe and don't 'interfere' ,

 

jens


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#7 Jens Piotrowski SOC

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Posted 23 April 2013 - 02:44 PM

Re RF, the HD-SDI signal is transmitted in the 1.5 to 4.5 ghz range and is very fragile.

I know of issues with carbon fiber posts and HD-SDI signals since they are conductive...talk to Curt @ Artemis
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#8 JensSchroeder

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Posted 24 April 2013 - 02:06 AM

Re RF, the HD-SDI signal is transmitted in the 1.5 to 4.5 ghz range and is very fragile.

I know of issues with carbon fiber posts and HD-SDI signals since they are conductive...talk to Curt @ Artemis

Thanks Jens, good to know

 

(und Gruesse zurueck)


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