User's Manual

350-Watt Digital VHF LB Transmitter Chapter 2, System Description, Maintenance &
Remote Control Connections
DT325B, Rev. 0 2-7
hold the IF Processor module in a mute
state.
Operate Mode with Mute Condition
The transmitter will remain in operate
mode but will be placed in mute when
the following fault conditions exists in
the transmitter.
• Upconverter is unlocked
• Upconverter module is not present
• IF Processor module is not present
Entering Operate Mode
Entering the operate mode can be
initiated a few different ways by the
transmitter control board. A list of the
actions that cause the operate mode to
be entered is given below:
• A low on the Remote Transmitter
Operate line.
• User selects "OPR" using switches
and menus of the front panel.
• Receipt of an “Operate CMD” over
the serial interface.
There are several fault or interlock
conditions that may exist in the
transmitter that will prevent the
transmitter from entering the operate
mode. These conditions are:
• Power Amplifier heat sink
temperature greater than 78°C.
• Transmitter is Muted due to
conditions listed above.
• Power Amplifier Interlock is high
indicating that the amplifier is not
installed.
Standby Mode
The standby mode in the transmitter
indicates that the output amplifier of the
transmitter is disabled.
Entering Standby Mode
Similar to the operate mode, the
standby mode is entered various
different ways. These are:
• A low on the Remote Transmitter
Stand-By line.
• Depressing the “STB” key on
selected front panel menus.
• Receipt of a “Standby CMD” over the
serial interface.
Auto Standby Mode
The FCC requires that certain
transmitters automatically switch to
standby operation on loss of input. The
transmitter incorporates this feature as
a user configurable setting. When Auto
Stand-By On Modulation Loss is selected
in the set-up menus, the transmitter
temporarily switches to standby after
ten seconds of modulation loss. When
the modulated signal as reported by the
IF Processor module is again present,
the transmitter automatically returns to
Operate mode.
RF System Interlock
A RF System Interlock signal is provided
through TB30-5. When this signal's
circuit is completed to ground such as
through a wire between TB30-5 and
TB30-15, the transmitter is allowed to
operate. If this circuit is opened, the
transmitter switches to a Mute condition.
This circuit may be completed through
coax relay contacts or reject load
contact closures to assure the RF output
system is available to receive the
transmitter's output RF signal.
Operating Frequency
The transmitter controller is designed to
operate on UHF frequencies. The exact
output frequency of the transmitter can
be set to one of the standard UHF
frequencies, or to a custom frequency
using the software channel set-up menu