User's Manual

Digital UHF Transmitter Chapter 2, System Description and
Customer Remote Connections
DT835A, Rev. 1 2-1
Chapter 2
System Description and Customer Remote Connections
MAJOR ASSEMBLY NUMBER TRAY/ASSEMBLY NAME
A1 Single UHF exciter assembly
A2 and A3 two 2-3kW amplifier array assemblies
A4 Hybrid combiner assembly
A7 Directional coupler assembly
Output coupler assembly
DM8-R digital modulator tray
Table 2-1: DT835A Major Assemblies
2.1 System Overview
The DT835A is a complete UHF solid-
state television transmitter that operates
at an output power of 2000 watts to
3000 watts digital, depending on the
digital application. The DT835A is made
up of three cabinets: a UHF exciter
cabinet and two amplifier array cabinets.
The DT835A is made up of the trays and
assemblies shown in Table 2-1.
2.1.1 (A1) Single UHF Exciter
Assembly
The single UHF exciter assembly
contains (A1) a UHF exciter tray, a DM8-
R digital modulator tray, (A10) an
(Optional) 10 MHz reference generator
tray, (A3) a splitter, (A4 and A5) two
variable phase/gain trays, (A6) a
metering panel, (A8) an AC distribution
assembly, and (A9) a remote interface
assembly.
The DM8-R modulator tray can have an
external 10 MHz reference connected to
J3 on the rear panel or it will generate
and internal 10 MHz reference if no
external reference is supplied. The
Digital input connects to J2 on the
remote interface assembly that is cabled
to J2 on the DM8-R modulator. The
Output from the DM8-R modulator at J4
connects to J6 on the rear of the UHF
exciter tray. The Digital IF is wired to
J18 on the 5 section delay equalizer
board, 44 MHz (1072090). The
processed digital IF signal is then cabled
to the J32 on the ALC board (1265-
1305). The digital IF input must be
selected as the input. This is
accomplished by connecting the jumper
W11 on J29 between pins 2 and 3 on the
ALC board. The digital IF is wired
through the K3 and K4 relays to the rest
of the ALC board. The LED DS5, digital
IF modulator enable, should be lit. The
ALC board has the capability of
switching between two different IF
inputs, but in this case only the digital IF
input is used.
The output of the ALC board (-10 dBm)
connects to (A11) the UHF upconverter
board (1265-1310) in the upconverter
section of the UHF digital exciter. The
upconverter takes the LO and
heterodynes it with the IF; the signal is
then filtered to produce the RF on-
channel output.
The (A15-A1) UHF generator board
(1565-1109) is mounted in the UHF
Generator Enclosure (1519-1144) for EMI
and RFI protection. The board contains a
VCXO circuit and additional circuitry to
multiply the VCXO frequency by eight.
The output is split and provides an input
to the x8 multiplier circuitry as well as a
sample for the PLL board. The amplified
eighth harmonic is then fed to the SMA
output jack of the board at J3. Typical
output level of the signal is +16 dBm
nominal.
The (Optional) (A14-A1) 10-MHz
reference generator board (1519-1126)