LANTEK User Manual - Ideal Industries
LANTEK User Manual - Ideal Industries
LANTEK User Manual - Ideal Industries
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Chapter 3<br />
Structured Cable Field Calibration and Testing<br />
Troubleshooting Return Loss Problems<br />
Problem: Excessive Return Loss (Value of 10 dB or less)<br />
Probable Causes<br />
Open, shorted, or damaged cable.<br />
Installed cable, cable segments, or patch cord have improper<br />
characteristics.<br />
Damaged or worn cable or connectors.<br />
Poor punch-down.<br />
Factory splice in cable.<br />
Other Tests Affected Test Possible Result<br />
Attenuation<br />
May be high.<br />
Capacitance and Could be affected if the impedance<br />
Average Impedance mismatch is caused by cable damage.<br />
DC Loop Resistance May be high if due to a poor punch-down.<br />
Impedance Test<br />
Average impedance is derived from electrical delay and capacitance measurements.<br />
The results of this test are expressed in ohms. Average impedance testing can help<br />
identify physical damage to the cable, connector defects, or cable segments with<br />
incorrect characteristic impedance.<br />
This test uses capacitive measurements; therefore, it is necessary to specify the<br />
correct cable type in order to accurately perform the test.<br />
Note: If a CAT 3 cable is selected (specified as the cable type where PVC is used in<br />
the cable insulation) but a CAT 5 cable (where Teflon ® is used as the cable insulation)<br />
is actually used, the average impedance will be calculated incorrectly. To avoid this<br />
problem, be sure to specify the correct cable type.<br />
Impedance Errors<br />
Figure 3-18: Impedance Test Screen<br />
Impedance errors cause signal reflection and strength reduction. Average impedance<br />
of each pair should be equal to the LAN system impedance of 100, 120, or 150 Ω.<br />
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