User's Manual

Innovator CU0TD-1/CU0RD-1 – CU4TD/CU4RD System Description
ATSC Transmitter/Regenerative Translator
Instruction Manual, Rev. 1 14
drawer are displayed on the LCD Screen on the driver drawer. In the amplifier
drawer the input RF signal at J1, located on the rear panel of the drawer, is fed to
J1 on the 4 Way Splitter Board, which supplies four outputs, one to each 888A
amplifier pallet. Each amplifier pallet has approximately 15 dB gain. The
amplified outputs of the pallets are combined in the 4 Way combiner board whose
output is at J1. The RF is connected to J2 the 7/16” (1.1cm) Din RF output jack
located on the rear panel of the drawer. The 4 way combiner board supplies a
forward and a reflected power sample to the amplifier control board for metering
and monitoring purposes. The typical sample value at J6, a 50Ω BNC jack
located on the front panel of the drawer, is approximately 65dB down from the
output power level of the drawer.
In higher power systems, multiple amplifier drawers are used along with splitters
and combiners to produce the desired output. A System Metering Board
(1312666) provides forward, reflected, overtemperature and other parameters to
the exciter/driver drawer from the external power amplifier chain. The
CU2TD/RD is made up of a driver drawer, a two way splitter, two amplifier
drawers and a two way combiner with a reject load. The reject load provides
isolation protection of the operating power amplifier if the other amplifier fails.
One–half the power of the operating amplifier drawer connected to the combiner
will be dissipated by the reject load with the other half of the power going to the
output filters and the antenna. The CU3TD/RD is made up of a driver drawer, a
three way splitter, three amplifier drawers and a three way combiner with reject
load. The CU4TD/RD is made up of a driver drawer, a four way splitter, four
amplifier drawers and a four way combiner with reject load. The reject loads in
the multi-amplifier systems have thermal switches connected to them which
monitor the temperature of the load and provide the overtemperature fault, if it
occurs, through the system metering board to the exciter/driver drawer.
The On Channel RF output of the amplifier drawer either connects directly to the
digital mask filter and low pass filter and then to the antenna in single amplifier
systems or to a combiner, the digital mask filter, low pass filter, output coupler
and finally to the antenna in multiple amplifier systems. The output coupler
provides a forward and a reflected power sample to the system metering board
which detects the samples and supplies the forward and reflected power levels to
the exciter/driver drawer for use in the metering circuits.
Optional Dual Exciter System w/Axciter Modulator Trays
The typical optional Dual Exciter System contains a Remote Interface Unit, two
Axciter modulators, two CXB Exciter/Driver Assemblies, an Exciter Output
Routing Switch, a power amplifier tray, a pre filter coupler, a low pass filter, a
digital bandpass filter, a post filter coupler and an output coupler. The system
also contains two Axciter relays, two 2 way splitters, a signal routing board and
two system metering boards which generate forward and a reflected power
samples for metering purposes in the exciter/driver assemblies.
The Remote Interface Unit monitors that state of the exciters and provides
automatic exciter switching based on current conditions and operator inputs. The
two exciters are configured as either the main On-Air exciter or the back-up
exciter. Either exciter can be used as the selected main exciter and the other
exciter functions in a backup role if it is not faulted.