LANcat
User Manual
Page 7-10
Signal generator
Signal measurement
1
2
M
3
6
Crosstalk
Figure 7-7. NEXT Measurement
The twisting of pairs of wires is essential to minimizing crosstalk
effects from pair to pair. The amount of twisting is a key difference
between high-performance Category 5 cable and lessor rated cable,
such as Category 3.
A common problem with installing Category 5 cable is
maintaining the wire twist when terminating the cable. The
EIA/TIA 568-A specification states the twists must be maintained
to within 0.5 inch (13 mm) of the termination for Category 5 and
within 1.0 inch (25 mm) for Category 4. If the twists are not
maintained, NEXT will increase.
NEXT also varies with the frequency of the signal, but the
relationship is not linear. Therefore, because the NEXT of a cable
is within a certain specification at lower frequencies does not
guarantee the NEXT will be within the same specifications at a
higher frequency. Figure 7-8 illustrates an example of how NEXT
varies with signal Frequency.
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