TM 11-6625-828-45
cycle component, and a decrease of 2 db in the 90-cycle
component for AMP LOC (needle left).
The ratio detector-discriminator, consisting of the
m. 90- and 150-Cycle Amplifier. Amplifier
network Z101 and CR105, CR106, produces the 30-
V105 is a duotriode amplifier which increases the 90-
cycle voltages used in the omni signal circuit, and the
and 150-cycle signal level output from the ratio network
90- and 150-cycle voltages used in the amplitude
described in 1 above. The amplified signal is applied
localizer signal circuit. The ratio detector-discriminator
through S102H to V104B. Demodulation amplifier V104B
connections are such that the 30-cycle output voltage is
raises the level of the variable 30-cycle signal or the 90-
maximum when the frequency of the frequency-
and 150-cycle signal as selected by S102H and applies
modulated input signal is minimum. This corresponds to
the amplified signal through R161 and C110 to the grid
a 180 phase difference between the reference and
of modulator V102.
variable channel signals. The output voltages of the
The modulation
ratio detector-discriminator are passed through a low-
frequency filter circuit as de- scribed in k below. Driver
components from V104B are applied to the grid of
V104A amplifies the level of the output signal from
modulator tube V102 through C110 and R161 and from
CR103, CR104, the variable channel limiter, before
V101B through limiter CR101, CR102 and C109.
entering the ratio detector-discriminator circuit.
Resistors R112 and R115 act to sup- press parasitic
oscillations. Capacitor C112 is a plate blocking capacitor
The output voltages from the ratio detector-discriminator
with a high value chosen to minimize a 30-cycle phase
are passed through filters to eliminate harmonics. Both
shift.
30-cycle low-pass filter and 90- to 150-cycle bandpass
filter networks are incorporated, the 30-cycle filter being
circuits for generating an amplitude-modulated, crystal-
connected for omni signals, the 90- to 150-cycle filters
controlled RF signal, and for demodulation of the signal.
for localizer signals. The 30-cycle filter consists of R138,
The RF signal is produced by a Pierce oscillator circuit in
R139, L106, C114A, C114B, and C121A, C121B, and
which either or two crystals, Y101 or Y102, is selected by
C121C. After passing through the filter, the 30-cycle
MC switch S105A. Two doubler circuits are used for
output is passed through a resistance network. For 30
raising the fundamental crystal frequency to the desired
omni courses, as selected by OMNI TRACK switch
output frequency. The final output frequency may be
S101, the network consists of resistors R140 and R141.
located anywhere between 108 and 132 mc. The
In the case of odd 15 omni courses selected by S101,
crystals normally supplied with the AN/ARM-5A produce
the network consists of R142, R143, and C122. This
output frequencies of 110.9 and 114.9 me. Other
network causes an additional phase shift. For 30
crystals (not supplied) may be used for other output
courses, the output is taken from the low end of R140
frequencies.
with a slight reduction in signal amplitude. For 15
courses, the output is taken from the junction of R143
V108A is connected in a modified Pierce circuit in which
and C122, reducing the signal amplitude an equal
one terminal of the crystal is grounded The plate
amount.
(terminal 6) of V108A is therefore at ac ground potential,
and the output load actually is located in the cathode
the ratio network is to set the relative levels of the 90-
circuit. The output of the oscillator is applied to the grid
and 150-cycle components derived from the ratio
of first doubler V108B through C141.
detector-discriminator circuit.
When MODULATION
switch S102 is in the AMP LOC ( (needle center)
V108B is connected in a doubler circuit, the tuned plate
position, these voltages, taken from the junctions of
circuit of which consists of choke L112, and either
R145 and R146 and R147 and R148, are equal' and
C143A or C143B as chosen by the setting of MC switch
each provides 20 percent modulation of the carrier.
S105B Tuning of this output circuit is accomplished by
Resistors R146 and R148 are selected to produce this
front- panel screwdriver adjustments which vary the
result. For the AMP LOC O (needle left) and AMP LOC
setting of the capacitors. The output of V108B
) (needle right) switch positions, the voltages are
unbalanced to produce 3-dot deflection on a cross-
pointer meter of a standard localizer receiver. This
corresponds to an increase of 2 decibels (db) in the 150-
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