(2) On the front panel of the HVPS, a
fuse is a primary fuse to the other four. A crowbar
MONITOR meter and associated selector switch permit
overload protection thyristor will blow this fuse under
the observation of various voltage and current levels
certain fault overload conditions. The 280-Vdc power to
within the power amplifier group. Operating conditions
the low-voltage module is fused by the LV fuse.
h. Amplifier/Mixer. During multicarrier operation,
are indicated by five STATUS lamps. These include
STANDBY, OPERATE, HV INHIBIT, FIL INHIBIT, and
the amplifier/mixer combines the SHF outputs of two,
WG/ANT INHIBIT. The STANDBY or OPERATE lamp
three, or four upconverters onto a single cable for driving
will light, according to the position of the OPERATE-
a PA. The unit consists of power combining circuitry
STANDBY switch. STANDBY indicates that the high
which provides isolation between the four input ports, a
voltage is inhibited, but the RF amplifier is ready to
low-distortion broadband TWT (or FET) linear amplifier,
Illumination of the HV INHIBIT lamp is
monitor and alarm circuits and power supplies.
lamp indicating the cause of the inhibit.
of the amplifier/mixer. SHF output signals from the
(3) The five FAULT lamps are BODY OVLD,
upconverters enter the SHF combiner. Front-panel
HV ARC, INTERLOCKS, TEMP-LOAD, and TEMPKLY-
LEVEL ADJUST controls provide for input level
STRON. Body overload and high voltage arc faults will
balancing. The SHF MONITOR meter indicates the level
cause the high voltage to be inhibited until the reset
of the channel selected by the coaxial selector switch.
switch is depressed and released. The temperature
The combined signal is routed to the SHF drive
faults will inhibit the high voltage until the over-
assembly, where the OUTPUT LEVEL control adjusts
the drive level to the TWT amplifier to control the TWT
INTERLOCKS fault indicates that the BLOWER circuit
output, TWT amplifier output is applied to the SHF output
breaker is off, or that RF amplifier or HVPS covers are
assembly, where it passes through a bandpass filter.
not in proper position.
The filtered output is connected to the front-panel SHF
(4) Four fuses labeled HV1, HV2, HV3, and
A14, A15, A16, and A17, respectively. The HV MAIN