Posted by Richard Crowley on 01/31/08 15:37

<blackburst@aol.com> wrote ...
> SDI signals, we are counseled, must travel along the shortest possible
> cable route, so as not to encounter the "cliff-effect," where the
> signal vanishes unless it is equalized and reclocked (akin to a
> "repeater"). The typical maximum distance without reclocking is 15
> meters (about 50 feet).
>
> This is all well and good for typical control room cabling, which
> usually runs anywhere from 6 inches to 20 feet per cable. But what
> about cameras? Camera pickup CCDs are, by nature, analog, and the
> conversion to SDI would best be done in the camera head, and sent
> along the multicore/triax to the camera control unit, and out of an
> SDI output. But, does this limit camera cables (which cannot contain
> reclockers) to 50 feet???

1) Cameras don't necessarily use "SDI" to send video from
camera to CCU.
2) CCUs have special electronics that adjust (manually or
automatically) for camera-cable losses.

>
> Some cameras/CCUs send the signal component analog along the cable,
> and convert it to SDI at the CCU. But what is the point of doing the
> conversion just a few feet from the switcher, or whatever destination?

The point is to interface with equipment with SDI inputs.

> An alternative is to run a separate SDI BNC cable from the camera
> head, all the way to the switcher; but again, are we limited to 50
> feet??? (JVC uses this scheme with the studio version of their GY-
> HD250).

Why do you think you need SDI out of a single camera?

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