Fluke DTX Series - NEXT (Near-End Crosstalk)

DTX Series CableAnalyzer
Technical Reference Handbook
3-20
NEXT (Near-End Crosstalk)
NEXT results show the crosstalk attenuation between
cable pairs. NEXT is the difference in amplitude (in dB)
between a transmitted signal and the crosstalk received
on other cable pairs at the same end of the cabling.
Higher NEXT values correspond to better cabling
performance.
Because of insertion loss, crosstalk signals occurring
farther from the signal source are weaker and cause less
trouble than crosstalk nearer the source (Figure 3-14). For
this reason, NEXT is measured from both ends of the
cabling.
For NEXT failures, the testers diagnostic screens (
J
Fault Info) may show more than one possible cause for
the failure. In this case, you can use the HDTDX analyzer
results to further diagnose the problem. See Chapter 4
for details.
Figure 3-15 describes the NEXT plot.
Note
For ISO/IEC 11801-2002 and EN50173:2002
standards, NEXT is not evaluated where
insertion loss at the same frequency is less than
4 dB.
Signal
source
Resulting
NEXT
Crosstalk near
the source
Crosstalk farther
from the source
amd89f.eps
Figure 3-14. Near-End Crosstalk (NEXT)