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VGA – AUDIO – RS232 EXTENDERS
3.2 UTP Cable Recommendations
RED
GREEN
BLUE
UTP cables have 4 twisted pairs inside. The video transmission over UTP uses
3 individual pairs for each color (Red, Green, & Blue). As shown in figure 3.2
above, a characteristic of Category-5/5e/6 cable is that the pairs of wires are
twisted at different rates. Therefore, for a given length of Cat-5 cable the total
length of a particular pair could be longer than others. Since the signals travel in
the cable at a fixed speed, the arrival times of signals can 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. Hall Research
highly recommends the use of UTP cables specifically constructed for video
transmission. In these cables the all the twisted pairs are the same length. They
are available from several sources including Hall Research (part numbers
shown below).
Zero-Skew CAT5 Cable for use with Hall Research CAT5 Products
PART NUMBER
CUTP-Z-1000-BLK 1000 ft.
Zero-Skew CAT5 cable. Bulk spool of 1000 ft
CUTP-ZP-1000-BLK 1000 ft.
Zero-Skew CAT5 cable. Bulk spool of 1000 ft Plenum Rated
If you are going to use commercial grade UTP cable, then we recommend using
Cat5 or Cat5e rather than Cat6, since the twist ratio match is better in Cat5
cable.
6
Figure 3.2
RED
GREEN
BLUE
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