Hall Research URA-232-XT - Manual (Page 12)

Model URA-232 & URA-232-XT
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3.4 Why Skew Adjustment?
UTP cables have 4 twisted pairs inside. The Hall Research UVA/URA video
transmission on UTP uses 3 individual pairs for each color (Red, Green, & Blue).
Figure 6 - skew mechanism, example
As shown in the figure above, a characteristic of CAT5/5e/6 cable is that the pairs of
wires twist at different rates.
Therefore, for a given length of CAT6 cable the total length of any particular pair
could be longer than other pairs in the same cable. Since the signals travel along the
length of each pair at a fixed speed, the arrival times of signals will be skewed in a
long cable (those that have to travel farther arrive later and the corresponding color
shifts to the right).
This is seen on the monitor as separation, or lack of convergence in colors. For
example, a vertical white line on the screen may look to have a red tinge on the left
edge and blue tinge on the right edge.
This effect gets worse at high resolutions, high refresh rates, long cables (in excess
of 200 feet), and depends on the cable construction itself.
If you are using special UTP cables that are specifically designed for video
transmission (such as Hall Research Zero-Skew™), then there should be no shift in
color alignment regardless of the cable length. However, in many applications
standard and common CAT6 cables may be utilized, this will necessitate a receiver
that can also move each color component to the left and right in order to realign
them.