Hall-research UVA-8 User Manual download pdf (Page 10)

Model UVA-4 and UVA-8

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 5 - 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 CAT5/5e/6 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 viewed 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 CAT5/5e/6 cables can be utilized, this will necessitate a

receiver that can also move each color component to the left and right in order to

realign them.

300 ft of CAT6 (1280x1024 source)

* actual zoomed photo of screen *

After skew adjustment

Figure 6 – Example of Skew manifested

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Hall-research UVA-8 User Manual Page 10