UHF Analog Driver/Transmitter/
Chapter 4, Circuit Descriptions
Translator
LX Series, Rev. 3
4-1
Chapter 4
Circuit Descriptions
4.0 (Optional) Exciter Switcher Tray,
(110 VAC 1305727 or 220 VAC
1305715); Appendix B)
NOTE:
Part of a dual exciter system.
4.0.1 Exciter Switcher Control Board
(220 VAC 1305704 or 110 VAC
1305725; Appendix B)
The Exciter Switcher Control Boards for
220 VAC and 110 VAC are the same
except for the location of the T1
transformer. Location T1-110 is used
with 110VAC input and location T1-230
is used with 230VAC input. Refer to the
schematic for the board 1305705 Page 3
of 4, located in Appendix B, for a visual
representation of the wiring.
The Exciter Switcher Control Board
monitors and controls both Exciters and
controls automatic switching of the
Exciters in case of malfunction in the On-
Air Exciter using a coaxial relay. ICs on
the board monitor the operating
parameters of the Exciters and determine
if the Exciters are functioning properly.
The front panel of the Exciter Switcher
has an LCD display, which provides set
up screens for the operation of the
switching process.
The coaxial relay has four “N” connectors
that provide input and output
connections to the relay. The RF Output
from Exciter “A” connects to J21. The RF
Output from Exciter “B” connects to J23.
The Selected Exciter RF Output to the
external amplifiers connects to J24. The
Exciter “A/B” Load connects to J22, to
which the RF output of the Off Air Exciter
is connected. An internal wire harness
connects the relay to J14 on the Exciter
Switcher Control Board. These
connections provide the control voltages
to the relay from the control board and
status indication connections back to the
control board.
4.1 (A1) Receiver Module (1304002;
Appendix B)
NOTE:
Not present in a transmitter
system.
4.1.1 IF ALC Board (1304003;
Appendix B)
The board provides the interface between
the receiver and the backplane and also
contains the control and ALC circuits for
the sled.
The control portion of the board consists of
a microcontroller (U8) and its associated
components that communicate to the
outside world via an RS-485 serial data
link. The microcontroller receives various
metering and alarm functions such as AFC
and ALC voltages, PLL and ALC faults and
communicates them back to the system
controller for display on the transmitter’s
LCD display. It also receives the channel
information from the system controller,
and converts it to the programming data
for the PLL chip on the Mixer/PLL Board in
the receiver.
The IF portion of the board consists of an
input pin attenuator, which is used to
normalize the gain of the board to account
for variations in the input level to the
board. The pin attenuator consists of
DS1, DS2 and associated components.
The signal is then amplified by U2-U4 and
associated components and applied to a
SAW filter that rejects any out of channel
signal that made it through the receivers
RF front end. Amplifiers U5, U6 and their
associated components are used to
amplify the signal to make up for the loss
through the filter. The final output of U6 is
split by a lumped element Wilkinson
splitter consisting of C21, C26, C27, L12,
and L14. The output from one of the
output ports is sent to the output of the
receiver, and the other output is
connected to a peak detector and used by
the ALC. The ALC circuit, consisting of
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Страница 105: ...APPENDIX C TRANSMITTER LOG SHEET...
