System Description Chapter 2

100 Watt High Band VHF Transmitter Chapter 2, System Description
420A, Rev. 0 2-3
A5) 2-way combiner board. The RF
output from the 2-way combiner board
(+51 dBm) is fed through (A31) an
output coupler board (1088-1104) that
provides a forward power sample to
(A19) the visual/aural metering board
(1265-1309). A forward sample connects
to the transmitter control board that
supplies the voltage sample to the front
panel meter of the tray. The reject port
of the output coupler board provides the
reject sample to the visual/aural
metering board. The metering board
connects the reflected sample to the
transmitter control board for VSWR
cutback and front panel-reflected
metering for the tray.
2.1.4 Bandpass Filter Assembly
The output from the (A1) 100-watt, high-
band VHF exciter/amplifier tray is fed to
the input of the (A2) bandpass filter
assembly. The signal is fed to the (A2-
A1) 5-section bandpass filter with traps
and then through (A2-A2) a high-band
VHF coupler assembly that provides a
filtered RF sample for test purposes.
2.1.5 Operational Voltages
The transmitter needs an AC input of 115
or 230 VAC at 10 amps connected to it,
through the AC power plug, in order to
operate. The tray is set at the factory to
operate at the proper input voltage. This
is accomplished by setting the (A1)
power entry module to the correct line
voltage.
2.1.6 Configuration of the Power
Entry Module AC Input
For 115 volts, verify that 115V is
indicated on the rear panel cover on the
power entry module. If it is not, gently
open the cover, remove the fuse
assembly, and reinsert it so that 115V is
visible with the cover closed.
For 230 volts, verify that 230V is
indicated on the rear panel cover on the
power entry module. If it is not, gently
open the cover, remove the fuse
assembly, and reinsert it so that 230V is
visible with the cover closed.
The input AC voltage connects from the
jack (J14), which is part of (A1) the
power entry module on the rear of the
tray, to (CB1) a 10-amp circuit breaker
that is also on the rear of the tray. The
switched AC is wired through (A1) the
power entry module. This module
contains two fuses, one on each line, to
the terminal block (TB2). TB2 has four
MOVs mounted to the terminal block, one
connected from each leg of the input AC
to ground and one across each of the two
legs, for surge and transient voltage
protection of the tray.
The input AC is wired from TB2 to (A28)
the switching power supply and to (A2) a
toroid transformer. The (A28) switching
power supply (1063547) provides the
+48 VDC to operate the amplifier
assembles and also to (A10) the +48
VDC fan in the tray. The step-down
toroid (A2) supplies two 16 VAC outputs,
through the terminal block (TB2), to (A3)
the +12V(4A)/-12V(1A) power supply
board (1265-1312). The AC connects on
the board to two full-wave bridge
networks for +12 VDC and one full-wave
bridge network for -12 VDC. The rectified
DC from the +12 VDC full-wave bridge
networks is connected to the (U1-U4)
current limiting voltage regulator ICs.
The rectified DC from the -12 VDC full-
wave bridge network is connected to the
(U5) current limiting voltage regulator
ICs. The ±12 VDC outputs connect to the
rest of the boards in the tray through
jacks (J3-J8).