LANTEK User Manual - Ideal Industries

Chapter 3
Structured Cable Field Calibration and Testing
Troubleshooting Attenuation Problems
Problem: High Attenuation Reading
Probable Causes
Poor connector termination points.
Excessive cable length.
Incorrect or poor quality adapter cable.
Incorrect cable.
Other Tests Affected Test Possible Result
DC Loop Resistance May be high.
Capacitance
May be high.
Length
May be over limit.
NEXT
May be low on pair combinations.
Average Impedance May be low.
Return Loss
May be over limit.
Return Loss Test
This test measures the ratio of reflected to transmitted signal strength. Good quality
cable runs will have little reflected signal, indicating good impedance matches in the
run’s various components.
Return Loss Errors
Figure 3-17: Return Loss Test Screen
Like attenuation, excessive return loss reduces signal strength at the receive end. It
also indicates a mismatched impedance at some point along the cable run. A value of
20 dB or greater indicates a good twisted pair cable. A value of 10 dB or less is
severe, and causes a large reflection of signal back to the source.
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