Instruction Manual

Table Of Contents
Length (m/ft) = V/I/R
where:
V = voltage drop in one leg of the loop (max = 0.5 V)
I = current the base radio draws during DC operation
R = resistance of the wire being considered (in Ohms per ft)
For common wire sizes, the maximum distances shown in Table 34: DC Power Connection Wire
Gauge Maximum Distances for an IV and D Site on page 103 apply.
Table 34: DC Power Connection Wire Gauge Maximum Distances for an IV and D Site
AWG Resistance (ohm/304.8 meter/ 1000 ft) Maximum Distance (for 13A)
2 0.1563 75 m (245 ft)
3 0.1970 60 m (195 ft)
4 0.2485 47 m (155 ft)
5 0.3133 37 m (120 ft)
6 0.3951 30 m (95 ft)
3.4.4.3
DC Power Connection Wire Gauge Calculations for HPD
Since the power supply disconnects itself from the DC input when it senses that DC voltage has
dropped to 42 VDC, it is important to minimize the voltage drop in the DC power supply loop (the total
length of the 48 VDC hot wire and the DC return wire) to no more than 1 V total. Minimizing the voltage
drop ensures that the maximum energy is removed from the battery before disconnecting the power
supply from the DC input line.
A base radio transmitting at 50 W draws up to 7.4 A current when operating from a 54 V source
(nominal 48 VDC system). As voltage decreases (due to the standby battery discharging) the current
increases proportionally (since the base radio appears to be a constant power load). At the low voltage
disconnect point (42 V for a nominal 48 VDC system), the current will be up to 9.5 A. Use of smaller
gauge wire would reduce this length depending on the resistance of the wire. To determine the
maximum length of wire for wire other than 2 AWG, the following relationship can be used:
Length (ft) = V/I/R
where:
V = voltage drop in one leg of the loop (max = 0.5 V)
I = current drawn by the base radio during DC operation (9.5A)
R = resistance of the wire being considered (in Ohms per ft)
For common wire sizes, the maximum distances shown in Table 35: Power Connection Wire Gauge
Maximum Distances for HPD on page 103 apply.
Table 35: Power Connection Wire Gauge Maximum Distances for HPD
AWG Resistance (ohm/1000 ft) Maximum Distance
2 0.1563 102m (335 ft)
3 0.1970 81m (265 ft)
4 0.2485 64m (210 ft)
MN003286A01-H
Chapter
3: GTR 8000 Base Radio Installation
103