Diagnosing Twisted Pair Cabling Faults
The HDTDR Analyzer 4
4-15
A Open on pair 7, 8 near the smart remote. A positive
reflection indicates an increase in impedance. Opens
are large increases in impedance and create large
positive reflections
B Short on pair 3, 6 near the smart remote. A negative
reflection indicates a decrease in impedance. Shorts are
large decreases in impedance and create large negative
reflections.
C Bad connection or kink near the smart remote. The
reflection for this example starts with a positive pulse.
This indicates that the fault has higher impedance than
the rest of the cable. A fault with lower impedance
would start with a negative pulse.
D Cable section with higher impedance than the rest of
the cable. The bad cable section is near the smart
remote. Note the positive pulse where the impedance
increases at the beginning of the bad section, and the
negative pulse where impedance decreases at the end
of the bad section.
E A spool of cable with poor return loss. This cable
produced a FAIL* result. The cable produces reflections
along its entire length.
Figure 4-4. Interpreting HDTDR Plots (cont.)
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