
Chapter 6: Diagnose Copper Test Failures
Causes of Twisted Pair Test Failures
189
Length gives a FAIL result
Link is too long (may need to remove coiled service loops)
NVP is set incorrectly
Note
To do the length test continuously while you look for
a fault, tap TOOLS
> Single Tests > Length.
Length exceeds the limit, but the length test did not fail
If the length of the shortest pair does not exceed the limit by 10 %, then the
length test passes even if other pairs exceed the limit. This is the 10 % rule for
length, as given in the ANSI/TIA standard. See the Fluke Networks Knowledge
base for details.
Propagation delay or delay skew gives a FAIL result
Link is too long (may need to remove coiled service loops)
Cable has different insulation materials on different pairs. This causes
differences in the twist ratios, which causes differences in propagation
delays among pairs.
“Bad patch cord” message (indicates excessive crosstalk over the first or last
2 m of the cabling)
Wire pairs are untwisted too much in the RJ45 plug
Poor quality patch cord used for channel
Cable on a permanent link interface adapter is badly distorted or
damaged
Wrong test standard selected
Table 8. Causes of Twisted Pair Test Failures (continued)
Summary of Contents for CableAnalyzer DSX-5000
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