switched on, it supplies 115 volts ac and 28 volts dc to
the omega receiver.
ANTENNA COUPLER. The AS-2623/
ARN-99(V) antenna coupler has two loop antennas
mounted at 90-degree angles to each other and at
45-degree angles to the aircraft centerline. These
antennae are directional, and the proper antenna
selection is based upon location to the station being
received, relative to the heading to the aircraft. One
of the four antenna lobes is selected (A+, B+, A-, or
B-) to give the receiver-converter the maximum
signal strength from the desired omega ground
station. Once the omega has been synchronized, the
antenna selection process is automatically controlled
by the central computer.
ARN-99(V) receiver-converter consists of five
sections. These sections are the receiver section,
correlator and digital converter section, computer
communication section, discrete storage section, and
the power supply section.
Receiver Section. The receiver section consists
of the antenna switching matrices, RF amplifiers, IF
amplifiers, and a precision frequency generator.
The antenna switching matrices sum and phase
shift the incoming signals to provide an antenna
configuration that will be best oriented to a specific
omega station. These circuits also enables test signals
to be injected into the omega system. There are three
of these matrices in this section, one for each of the
The RF amplifiers remove the IF image and
provide attenuation to remove signals far from the
operating frequency. There are three of these circuits,
one for each frequency, with the only difference
between them being the tuning of the bandpass filters
and the notch filters. The heterodyne mixers are
identical for all three.
The local oscillator frequencies produce a 1.33
kHz IF signal. Each frequency used has its own IF
amplifier circuit; these circuits are identical for all
Figure 2-15.-Omega power control panel.
three frequencies. The limiters in the circuit control
the dynamic signal level in the amplifier, preventing
saturation of the linear filters.
The precision frequency generator generates the
precision frequency signals required for operation of
the system. The generator consists of a 10.608 MHz
crystal oscillator and counters. The counters divide
the oscillator frequencies to provide a 13.6 kHz RF
test signal, a 1.133 kHz IF reference signal, a 14.733
kHz local oscillator signal, a 176.8 kHz receiver-
computer input/output clock signal, a 11.333 kHz RF
test and local oscillator signal, and a 10.2 kHz RF test
and local oscillator signal.
Correlator and Digital Converter Section.
This section converts the phase of the IF signals into
digital form. The three channels use identical phase
The phase of the IF signal is the
navigation information needed by the central
Computer Communication Section. The
receiver-converter operation is computer controlled
and cannot be operated manually. This section
provides a means of communication between the
receiver-converter and the central computer. This
section receives data requests from the computer and
sends the desired data to the computer.
Discrete Storage Section. This section
provides a means of storing and controlling antenna
switching and test signal gating commands from the
central computer for use in the receiver-converter.
The discrete storage consist of control line drivers and
a decoder circuit. It acts as an interface between the
communication section and the receiver sections.
Power Supply Section. The power supply
generates regulated and unregulated dc voltages for
the system. The power supply also provides for
short-circuit protection and for overvoltage
protection. The short-circuit protection is for the
three regulators, (+16, +5, and -16 Vdc regulators). A
short in any of these will cause the regulator to be
clamped to ground, and the power supply will need to
be reset. The overvoltage protection is for the +5 Vdc
circuit. When the output of the +5 Vdc exceeds the
breakdown voltage of the Zener, a relay is energized
that removes the input power. When this occurs,
system power needs to be cycled to reset the