| Electronics > Beginners |
| Testing 12G-SDI cable |
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| misquamacus:
I work in video production, and have purchased a spool of Belden 4855r coax cable to make my own custom cable runs. Right now I am testing them by simply connecting two components together to see if a signal goes through, but I'd like to test them more comprehensively. How does one check for things like the actual strength of the signal from one end to the other. https://www.iewc.com/assets/specsheets/spec_4855r_belden_4k%20uhd%20coax.pdf Any advice would be greatly appreciated. Thank you |
| BrianHG:
It's been awhile, but, when I was testing development of 3G SDI hardware for distance on 3G cable, 1 thing was a must, do not test the cable on the spool. It will almost always work. You must have the cable off the spool, running huge straight lengths even if you need to make a few loops around the outer perimeter of the office. The signal in the cable degrades that way as stray interference begins to penetrate the coax shielding which does not happen in a compact spool as only the outer edges of that spool have to deal with the bulk of such external emi. |
| dmills:
A Tek Prism or similar with the 12G physical layer option ($$$) or a VNA capable of S parameters to at least 25GHz (Would be my preferred option, slightly cheaper and more generally applicable, but you want the 75 ohm option). The elephant in the room is usually cable termination, closely followed by things like installation bend radius and not crushing the cable by over tightening the cable ties (Some installers can be a little heavy handed). I will admit to being a little surprised to see 12G single link being used, it tends to be a Japan and Korea thing at the moment in my experience, the US seems to be doing the quadlink 3G thing (Pain in the arse that is), and EU is going hard for the 2022-6 and 2110 IP approach for all that both are still more then a little immature on the control and system timing fronts (There is sometimes even a little TECO in there but the football types seem to have decided that any compression is a no go, so...). Regards, Dan |
| misquamacus:
Thanks very much Dan and Brian! It sounds like proper testing myself will be too expensive, so I'll try to hire someone with the proper equipment. @dmills, I'm with you on the single link 12G, but a lot of this is being pushed through by companies like Blackmagic Design. They started selling 12G equipment to people before the SMPTE standards were even ratified. |O |
| dmills:
BMD the Bheringer of broadcast! Nobody shopping BMD has any actual need for 12G :palm: I mean the glass you need to actually manage to capture 4K, never mind the sensors means that even if you are shopping GV or the like you probably don't bother with the 4K option for most things. Yes, I know BMD advertise a "4K" camera but there is not much point in outputting 4K if the sensor and glass are not up to the job. The Japs are going 12G on fibre, the Koreans on coax, Europe is mostly ignoring 12G as an SDI thing and going IP (Now they have finally ratified 2110, shame the control layer is still a bit of a puzzler), and the yanks seem to be mostly doing quadlink..... Regards, Dan. |
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