Extron electronics Twisted Pair Receiver VTR001, User Manual

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VTT001 and VTR001 • Installation
increases, the amount of skew increases. Skew affects the
displayed image when the differential length between wire pairs
exceeds two feet, causing the timing of the red, green, and blue
video signals to appear out of alignment (horizontal registration
errors). A white vertical line on a black field can appear as
individual red, green, and blue lines that are close together; the
signal transmitted on the shortest wire pair leads the other
colors and appears to the left on the display.
UTP cable test equipment measures and reports wire pair
length. The report on the various
pair lengths can be used in
equalizing pair skew. The nominal
velocity of propagation (NVP —
the speed at which the signal
travels on the transmission line,
measured as a percentage of the
speed of light) of TP cable is very
close to that of conventional
coaxial cable. The difference in
NVP means that an additional
length of coax equal to the length
of pair skew, placed on the
receiver’s output, equalizes the
effects of pair skew.
CAT 5 TP cable can lead to
registration errors between the red, green, and blue video
signals. Pair skew can be measured with test equipment or
identified by viewing a crosshatch test pattern closely to
determine if either the red, green, or blue video image leads
(appears to the left of) the other two video images. These
images can be minimized or eliminated by one of the following
methods:
• Switch to Extron’s Enhanced Skew-Free A/V UTP cable.
• Add a skew compensation cable equal to the length of
pair skew to the receiver’s output.
• Install an Extron Skew Equalizer, SEQ 100 15HD
(part #60-676-01) or SEQ 100 BNC (part #60-675-01), on
the receiver’s video output and adjust the skew for the
leading video image.
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