Fluke DSX-600 - NEXT (Near-End Crosstalk)

Chapter 3: Certify Twisted Pair Cabling
Frequency-Domain Results
79
NEXT (Near-End Crosstalk)
NEXT results show the crosstalk attenuation between wire pairs.
NEXT is the difference in amplitude (in dB) between a transmitted
signal and the crosstalk received on other wire pairs at the same
end of the cabling. Higher NEXT values correspond to larger
differences between the amplitudes of the transmitted signals
and the crosstalk, which corresponds to better cabling
performance. Figure 35 shows the NEXT plot. The tester puts the
cursor at the worst margin.
Note
If the NEXT result is an an , the 4 dB rule applies.
See “About dB Rules” on page 90.
Because of insertion loss, crosstalk signals occurring farther from
the signal source are weaker and cause less trouble than crosstalk
nearer the source (Figure 35). For this reason, the tester measures
NEXT from both ends of the cabling.
For NEXT failures, you can use the HDTDX analyzer plot to locate
cause of the failure. See “The HDTDR Analyzer” on page 127.
GPU82.EPS
Figure 35. Near-End Crosstalk (NEXT)
Signal
input
Crosstalk near
the source
Crosstalk
farther from
the source
NEXT