User's Manual

350-Watt Digital VHF LB Transmitter Chapter 4, Circuit Descriptions
DT325B, Rev. 0 4-5
that supplies the information from the
selected source to the display. By
pushing the button again, a different
source is selected. This occurs for each
push button. Refer to Chapter 3 for
more information on the Display Menu
Screens.
4.1.4 (A2) Switching Power Supply
Assembly
The power supply module contains a
switching power supply, a terminal
blocks, V1, V2 & V3, for distributing the
DC voltages, and a 3 position terminal
block to which the AC Input connects.
Jack J1 connects to the Control Board
and supplies DC OK, at J1-4 & 3, and AC
OK, at J1-2 & 1, status to the control
board. A Power Supply enable connects
from the control board to the power
supply at V1B-6 & 7. The power supply
is configured for three output voltages
+12V, -12V, at the 10 position terminal
block, and a main output power of +32
VDC at J50 pin A (+) and J50 pin B
(Rtn). The power supply is power factor
corrected to .98 for optimum efficiency
and decrease in energy consumption.
For safety purposes all outputs are over
voltage and over current protected. This
supply accepts input voltages from 85 to
264 volts AC, but the power entry
module, for the exciter/amplifier chassis,
must be switched to the proper input
voltage setting, for the transmitter to
operate.
4.1.5 RF Output of Driver/Amplifier
Chassis Assembly
The RF output from the upconverter at
the upconverter RF output jack J23, a
BNC connector. The RF is cabled to the
“S” input Jack on the (A10) 2 Way
Splitter. One output of the splitter
connects to the VHF Amplifier Tray. The
other output of the splitter connects to
the triple peak detector board for
metering, ALC and monitoring purposes.
NOTE: Information and drawings on the
Axciter Modulator Tray, the Upconverter
Module and the Downconverter Module
are contained in the separate Axciter
Manual.
This completes the description for the
Driver/Amplifier chassis assembly.
4.2 (A3) VHF Low Band Amplifier
Tray (1304363; Appendix D)
The VHF low band amplifier tray is
adjusted at the factory for use as a
digital RF amplifier tray. The tray has
approximately 55 dB of gain at the
frequency of the VHF low band channel
and will take the typical +4 dBm DTV
input and amplify it to an output level of
approximately +55.8 dBm. As a DTV
amplifier, the tray is calibrated for 350
watts average power that is equal to a
100% meter reading. The tray is made
up of the boards and assemblies listed in
Table 4-1.
Table 4-1: VHF Low Band Amplifier Tray Boards and Assemblies
MAJOR ASSEMBLY
DESIGNATOR
BOARD/ASSEMBLY NAME DRAWING NUMBER
A1-A1
Phase shifter board (mounted in
[A1] an RF enclosure assembly)
1198-1602
A1-A2
Filter/amplifier board (mounted in
[A1] an RF enclosure assembly)
1198-1606
A2-A1
VHF low band amplifier board
(mounted in [A2] an RF enclosure
assembly)
1198-1605
A2-A2
Overdrive protection board
(mounted in [A2] an RF enclosure
assembly)
1198-1601