User's Manual

Digital UHF Driver/Transmitter Chapter 2, System Description,
Maintenance & Remote Control Connections
LX Series, Rev. 1 2-9
2.2 RF Output Assemblies
The RF output from the exciter power
amplifier is at the RF output jack, an “N”
connector J25, PA RF Output, of the
chassis assembly. If this assembly is
used as a driver the output connects to
the input of the PA Assembly or a splitter
for multiple PA Assemblies, mounted
beneath the Exciter Assembly. If this
assembly is used as a 5W to 50W
transmitter, then the output connects
directly to the bandpass filter for the
system.
The RF output of the transmitter is
typically connected to a low pass and
DTV mask filters mounted on the rear or
top of the cabinet assembly. The low
pass and DTV mask filters are tuned to
eliminate unwanted sideband and
harmonic frequencies.
2.3 Control and Status
The control and status readings of the
exciter/amplifier Chassis assembly are
found by operating the front panel
display screen on the front of the
assembly. Detailed information on the
use of the screens is found in chapter 3.
2.3.1 Front Panel Display Screens
A 4 x 20 display located on the front of
the Control & Monitoring/Power Supply
Module is used in the LX Series
transmitter for control of the operation
and display of the operating parameters
of the transmitter. Refer to Chapter 3
for descriptions of the screens.
2.4 System Operation
When the transmitter is in operate, as set
by the menu screen located on the
Control & Monitoring Module, the
following occurs. The IF Processor will be
enabled and the mute indicator on the
front panel will be extinguished. The
+32 VDC stage of the Power Supply in
the Control & Monitoring Module is
enabled, the operate indicator on the
front panel is lit and the DC OK on the
front panel should also be green. The
enable and DC OK indicators on the PA
Module will also be green.
When the transmitter is in standby, the
IF Processor will be disabled, and the
mute indicator on the front panel will be
red. The +32 VDC stage of the Power
Supply in the Control & Monitoring
Module is disabled, the operate indicator
on the front panel will be extinguished
and the DC OK on the front panel should
remain green. The enable indicator on
the PA Module is also extinguished.
If the transmitter does not switch to
Operate when the operate menu is
switched to Operate, check that all faults
are cleared and that the remote control
terminal block stand-by signal is not
active.
The transmitter can be controlled by the
presence of an input signal. If the input
signal to the transmitter is lost, the
transmitter automatically cuts back and
the input fault indicator on the IF
Processor module lights. When the input
signal returns, the transmitter
automatically returns to full power and
the input fault indicator is extinguished.
2.4.1 Principles of Operation
Operating Modes
This transmitter is either operating or in
the standby mode. The sections below
discuss the characteristics of each of
these modes.
Operate Mode
Operate mode is the normal mode for
the transmitter when it is providing RF
power output. To provide RF power to
the output, the transmitter is not in
mute. Mute is a special case of the