LANTEK User Manual - Ideal Industries

Chapter 3
Structured Cable Field Calibration and Testing
NEXT and ELFEXT Errors
Crosstalk is usually caused by poor connector termination on the ends of the cable. A
low value of dB measurement reading indicates presence of high crosstalk.
Troubleshooting NEXT and ELFEXT Problems
Problem: Low dB test readings
Probable Causes
Installed cable or patch cable not correctly rated.
Defective, poor quality cable or too many connectors.
Poor quality installation at the connection points.
Too much insulation has been stripped from the wires at
termination.
A pair of wires has been untwisted too much at termination.
Split-pairs.
Poor quality connectors or connectors not rated to desired
category.
Delay skew (ELFEXT).
Excessive noise entering the cabling system from external sources.
Other Tests Affected Test Possible Result
Return Loss
May be over limit.
NEXT
May show same symptoms.
Attenuation Test
This test measures the overall signal strength loss in the cable and verifies that it is
within acceptable limits. Low attenuation is essential for error-free transmission.
Attenuation is measured by injecting a signal of known amplitude at the Remote
Handset and reading the amplitude at the Display Handset.
Attenuation Errors
Figure 3-16: Attenuation Test Screen
Attenuation causes a loss of signal strength over a cable. The loss increases with cable
length, signal frequency, and temperature. Attenuation testing can be used to find
problems in the cable, connectors, or connecting hardware. A high value of dB test
reading indicates a high value of attenuation, leading to greater loss of signal.
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