Posted by blackburst@aol.com on 01/31/08 15:18

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???

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?

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).

If there are these kinds of limits, what is the purpose of SDI? Am I
missing something here?

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