1855 versus 1694

[NECRAT]

Has anyone of the TV guys here wired HDSDI using Belden 1855? (The real small video cable) How was the response and how well did it work?

--Mike

[eadler]

All BNC cables in our plant newer than 5-7 years are 1855A. Our entire HD part of the plant and much of the digital SD part of our plant is 1855A.
The only place I have an issue with it is on a SD GVG ViBE decoder feeding a GVG Kayak through a patch panel and router has immense jitter (the jitter only appears in this routing configuration with no patch cables installed). Bypassing the normaled patch with a cable on each side or completely bypassing the router alleviates this jitter. My guess is that there's a pinched cable somewhere but we use this configuration so rarely that it is of lower priority and I haven't had time to completely sniff it out.
We use 100'+ runs of 1855A for sync to and HDSDI video from two cameras on the floor of the studio, with an additional 80' or so to get them into the switcher and an additional 20' run up a jib arm and we do not have any issues (other than someone ripping off a connector by bending the cable hard at the camera -- solved this on the jib camera by making runs along the jib and terminating them at the camera and BNC barrels at the base, now they just connect at the loose cables on the jib base).

[PID_Stop]

Like Eric, we use 1855A for reference and short (typically <25') HD-SDI runs between racks. Longer runs of HD-SDI, especially on lines fed by non-reclocking amplifiers, are 1694A. We have absolutely no problems with either cable. Also, both types work fairly well for analog NTSC: better response than typical RG59 (e.g., Belden 8241) but not as good as 8281.

We're paying $326 per thousand feet of 1694A, and $256 per thousand feet of 1855A, so that's also something of a factor. (1505A is $268 per thousand, but we have stopped using it since it's not all that better than 1855A, is larger and stiffer to bundle, and doesn't work so well for analog video.)

-- Jeff

[eadler]

I believe that some of our early AES3id wiring and some of the early SDI wiring is 1505A. The only reason that I've needed to redo any of these (1855 or 1505) run is because someone destroys the connector or squeezes the cable in a floor tile...

[w9wi]

Our hub rack is wired with 1855. Works fine. Includes HD-SDI, reference, a bit of AES, and some ASI. It was wired in Atlanta, so I don't know what it's like installing connectors.

They included an extra long cable for testing. That cable has been quite a bit of abuse and is still working reliably.

We're still using 1694 for the rest of our plant.

[eadler]

I forgot to mention, I've also used the 1855A to run an L-band signal about 40' no problem and we use it for all of our ASI (now routed) and SMPTE310 and for AES3id and ASI (and 310) at transmitter sites (both TV and HDRadio). We've even used it for composite audio in a pinch. Honestly, I think I'd probably go to glass (reclocked, preferably) for any run too long for 1855A.

I should put ends on the full spool that I have and put the Tek analyzer and a display on one end and the Tek SDI generator on the other and measure how much jitter I need to add in the generator for it to become unstable at the analyzer/display (and compare it to 1' lengths of various cables).

[Kelly]

Cables don't actively add jitter to the signal, however they can slow the signal transitions or edges. When the edges are slowed, the receiver or buffer at the cable destination is less likely to detect the transition at the correct time with certainty, which results in jitter. Really it's a cable bandwidth issue.