Vector-LP Radio Beacon Transmitter Technical Instruction Manual Page 2-7
Section 2 Preparation for Use and Installation Issue 1.1
2.2.5 Antenna Feed Cable
The shield of the antenna feed coaxial cable
should be connected directly to the station
reference ground where it enters the
building. In addition, the centre conductor
and the shield of the feed cable should pass
through a ferrite toroid positioned between
the shield ground at the building entrance
and the shield termination at the transmitter
reference ground. This toroid is transparent
to the RF signal, but presents impedance to
transients originating in the antenna. When
Nautel’s
interface protection unit is installed,
the RF feed cable is connected directly to it.
It contains the necessary ferrite for the ac
wiring and RF feeder cable.
2.2.6 Antenna Tower
The antenna tower is the most likely target
for lightning strikes. It is imperative that it
contain lightning protection devices as the
first line of defense against lightning strikes.
2.2.7 External Control/Monitor
Wiring
All external control/monitor wiring that may
be subject to lightning induced transients
should be interfaced to the station reference
ground by surge protection devices at the
building entry. All conductors and shields
should pass through a ferrite toroid that is
positioned between its surge protection
device and the transmitter. This toroid is
transparent to control/monitor signals, but
presents impedance to lightning induced
transients. Connect shields to the ground
stud at the back of the transmitter, above the
cable routing channel (see Figure 2-2).
2.2.8 Electrical Power
The transmitter is configured during
manufacture to operate from an ac or dc
power source. The power source and
associated switching components and wiring
must meet the following requirements:
2.2.8.1 Ac Voltage Source
The VR250 can operate from a 170 to 270 V
ac, 50 Hz, (line-to-neutral) or 60 Hz (line-to-
line) ac power source. The VR125 can
operate from a 90 to 270 V ac, 50/60 Hz,
(line-to-neutral) or 60 Hz (line-to-line) ac
power source. The voltage must be
maintained within the specified voltage
range under all loading conditions. The
transmitter contains circuitry that maintains
the RF output at the pre-set carrier level for
voltage variations within this range. Power
consumption and line current depends on
the transmitter’s maximum rated power level
(see Table 2-1). Nautel recommends the ac
power source have a 20% over-capacity to
ensure adequate regulation.
Table 2-1: Ac Power Consumption
Vector
Product
Max. Power
Consumption
Max. Line
Current
VR125 500 VA *5 A RMS
VR250 1000 VA *5 A RMS
based on worst-case parameters (maximum RF
output power, minimum ac voltage and efficiency)
* maximum line current cannot exceed 5 A (ac
power entrance uses a 5 A breaker)
2.2.8.2 External Ac Switching
All current carrying conductors from the ac
power source should be controlled by an
external switching box located in close
proximity to the transmitter. This switch box
should be clearly marked TRANSMITTER
EMERGENCY ON/OFF SWITCH. Refer to
Table 2-1 for current ratings that should be
observed when selecting a circuit breaker
and associated input wiring.
2.2.8.3 Dc Voltage Source
As an option, the transmitter may operate
from a dc power source (battery bank).
x The dc source must provide a nominal
24 V (VR125 only) or 48 V. When a 24 V
battery is used in VR125 transmitters, a
24-48 V power supply (A16) is used to
boost the dc voltage. The no-load voltage
must be in excess of 44.0 V (or 22.0 V for
24 V sources, limit is adjustable) for the
transmitter to turn on initially.
x Line current depends on the
transmitter’s maximum rated power level
(see Table 2-2).
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