m 23x10-3
3.5.3. Loop Length
The method of determining subscriber loop length using the signal resistance limit as a basis is called the basic resistance design. The maximum subscriber loop length, which is defined as the distance from the subscriber to the central office, is expressed as
Loop resistance limit RL
dc loop resistance Rdc The dc loop resistance is measured in ohms per kilometer and expressed as
Where 'd' is the diameter of the conductor in millimeters.
Example 3.3. Calculate dc loop resistance, if the loop resistance limit is 1250 ohm for the loop length of 10 km.
Rdc L 10 km
From the equation 3.13 with the knowledge of dc loop resistance, the diameter of copper wire can be determined. The table shows American Wire Gauge (AWG) versus wire diameter and resistance. From the table 3.4, for the required diameter of the cable, the size of wire gauge can be determined.
GAUGE NO (AWG) |
diameter 'd' (mm) |
Rdc (Q/kM) |
Attenuation or loss per km (dB/km) |
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