Page 2-8
Vector-LP Radio Beacon Transmitter Technical Instruction Manual
Issue 1.1
Section 2 Preparation for Use and Installation
Table 2-2:
Dc Power Consumption
Transmitter
Max. Line Current
VR125
6.3 A (48 V); 12.6 A (24 V)
VR250
12.4 A (for 48 V)
based on worst-case parameters (maximum RF
output power, minimum dc voltage and efficiency)
x
The capacity of the dc battery bank and
the
Low Battery Voltage Threshold
setting, dictates the length of time the
transmitter will operate. When the battery
bank voltage falls below the low battery
voltage threshold (factory set for 42 V dc
for 48 V sources or 21 V for 24 V
sources; limit is adjustable), the
transmitter turns off and prevents the
battery from fully discharging.
x
Use an external circuit breaker for the dc
power source. There is an internal fuse
for the dc supply.
2.2.9 Antenna System
The antenna system must present 50 ± j0
:
impedance at the carrier frequency. The
transmitter will function while operating into
a maximum VSWR of 1.5:1, but overall
system performance will be degraded.
Circuitry within the transmitter will prevent
damage to the transmitter from high VSWR
loads. Refer to the associated antenna
tuning unit’s manual for further information.
2.2.9.1 RF Feed Cable
The RF feed cable must be a 50
:
coaxial
cable that is terminated by a type N coaxial
connector. The RF output connector of the
transmitter is located at the back of the
transmitter. If the transmitter is installed in the
deluxe or short cabinet mounting option, the
RF output connector is located on top of the
cabinet. If the transmitter is installed in the
IP66 cabinet mounting option, the RF output
connector is located on the side of the
cabinet.
2.2.9.2 Interface Protection Unit
An interface protection unit (SPU1) is
available from Nautel. It prevents lightning
induced transients from flowing through the
transmitter. Isolation of the transmitter and
the desired lightning protection is
accomplished by:
x
Inserting a 1:1 isolation transformer in the
RF feed cable to ensure there is no dc
connection between the transmitter's RF
output and the antenna system.
x
Passing all wires through ferrite toroids. A
toroid is an inductance transparent to
normal signals but presents impedance to
lightning induced transients.
x
Connecting suitably rated varistors
between the ac line and the station
reference ground.
x
Connecting the shield of the coaxial
cable from the antenna/phaser directly to
the reference ground.
When used, the antenna feed cable is
connected directly to the interface protection
unit. Fifty feet of coaxial cable is provided for
the connection between the interface unit
and the transmitter.
2.2.10 Internal DDS Source
The integral numerically controlled oscillator
is the RF drive source. Configure the
shorting posts on RF synthesizer PWBs (A5
and, if used, A8) as follows:
- E1 in
INT
position (pins 2 and 3 shorted)
- E2 in
INT
position (pins 2 and 3 shorted)
- E4 in
INT
position (pins 2 and 3 shorted)
