Product Manual

Product Manual for Tornado Radio Unit
41
8.2.3 ESSENTIAL POWER REQUIREMENTS
8.2.3.1 Voltage Range
The operating input voltage range of the power supply is 10.5 to 60 VDC. This means that the voltage must not
rise above 60 VDC under idle conditions or fall below 10.5 VDC at full load.
8.2.3.2 Static Power Input
The typical power drawn when the transmitter is active is about 21W (maximum 26W). This occurs when the two
transmitter channels are operating at full power. The power drawn via the internal switching regulators is nearly
independent of supply voltage, except for some additional converter loss at the top end of the voltage range, so
that the input current to the RU is almost inversely proportional to supply voltage, e.g. approximately 2.4A at 10.5V
or 0.5A at 56V This needs to be considered when the power source is remote from the RU and cable loss is a
factor.
Input Source Voltage (S)
Average Current in Amperes
= Iavg = 25/S
Circuit Breaker Current in
Amperes = Imcb = 1.5*Iavg
10.5 Volts
2.4 Amps
3.6 Amps
24 Volts
1.1 Amps
1.7 Amps
48 Volts
0.6 Amps
0.9 Amps
56 Volts
0.5 Amps
0.8 Amps
Table 1: Current draw
8.2.3.3 Starting Current
As long as the power supply can supply the static power it should be able to provide sufficient current during start-
up.
8.2.3.4 Supply Polarity (Isolated Power Supply)
Both the positive and negative connections of the power supply are isolated from the case and other circuitry. The
standard DC power cable supplied with an RU is twin 1.5mm (16AWG), approximately 2m long, terminated at the
RU end with a Phoenix Contact MSTB 2,5 HC plug. This cable is wired to pins 1 (positive) and 2 of the plug, which
employs screw terminal contacts.
Pin 1 – Positive (Red)
Pin 2 – Negative (Black)
Power supply connector
8.2.3.5 Grounding
The radio unit case must be grounded through an external earth strap. Generally, this is done to the local rack
frame, which in turn should be part of a well-designed station grounding system. This internal grounding is
designed for EMC and transient protection currents. The RU casting is tapped to take a M4 x 8mm screw for
grounding purpose.