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Chapter 6: Diagnose Copper Test Failures
Causes of Twisted Pair Test Failures
191
Return loss gives a FAIL, FAIL*, or PASS* result (continued)

Mismatches in cable construction (such as cable from different
manufacturers)

Water in the cable jacket (typically causes failures on all pairs at lower
frequencies)

Cable compression (tight cable ties, pinches, kinks, etc.)

Poorly matched plug and jack (6A/Class E
A
applications)

Wrong test standard selected

Defective link interface adapter
Note
The HDTDR analyzer can help you locate the cause of
a return loss failure. See page 204.
NEXT, PS NEXT, ACR-N, PS ACR-N, ACR-F, PS ACR-F gives a FAIL, FAIL*, or
PASS* result

Excessive untwisting of pairs at a connector

Poor quality patch cords

Poor quality connectors

Poor quality cable

Poorly matched plug and jack (6A/Class E
A
applications)

Incorrect link interface adapter

Cable compression that distorts the pattern of twists in the pairs (tight
cable ties, pinches, kinks, etc.)

Inappropriate use of couplers

Excessive noise source near cabling under test

Wrong test standard selected
Note
The HDTDX analyzer can help you locate the cause of
a NEXT failure. See page 194.
Correcting NEXT problems usually corrects ACR-F
problems.
Table 8. Causes of Twisted Pair Test Failures (continued)