TM 11-6625-828-45
modulated (fm) simultaneously at 90 and 150- cycles. In
V114. The grid bias applied to V114 is determined by
place of the 30-cycle filter used for omni signals, a 90- to
load resistor R196 and error amplifier Vl13 and voltage
150- cycle filter is connected, and a ratio network
reference V112 which are series-connected across the
replaces the resistor network. The 90- to 150-cycle filter
dc output of V111. Voltage reference V112 holds the
is used to pass the 90- and 150-cycle voltages produced
cathode of V113 at a constant reference potential of
by the ratio detector-discriminator, and to remove the
approximately 150 volts with respect to ground, while the
higher- frequency components. The ratio network, in
control grid of V113 is fed from the tap on the voltage
combination with the 90- to 150-cycle filter, functions to
divider, consisting of resistors R204, R202, and R198. If
set the relative levels of the 90- and 150-cycle
the load voltage rises, whether from a decrease in the
components. The ratio' detector-discriminator (Z101,
load current or from an increase in the input voltage, the
CR105, CR106) and modulation amplifier V104B
voltage on the grid of V113 rises, decreasing the bias,
function in the same way as in the omni positions of
while its cathode volt- age remains practically constant.
MODULATION switch S102.
The plate cur- rent of V113 increases thereby causing a
c. Output
Circuits.
The
modulation
larger voltage drop across load resistor R196. This
components developed in the omni and localizer signal
change in voltage will also be applied to the grid of V114,
circuits are amplified by modulator tube V102. This tube,
but with inverted form, causing the grid of V114 to
in turn, amplitude-modulates the RF signals generated in
become more negative; in effect, increasing the plate
RF unit Z104. The resulting RF output is made available
resistance of V114. Under these conditions, a larger
at a 1-volt level at 1 VOLT jack J105 or at an attenuated
portion of the available dc voltage will appear across
level from ATTEN jack J104. Detection of the modulated
V114 which tends to restore the output voltage. The
RF signals takes place within the RF unit, and the
action of the regulator circuit is reversed if the load
demodulated output is connected through cathode
voltage tends to fall. The low end of the voltage divider
follower V116A to DE- MOD output connector J107. The
(R204, R202, and R198) is re- turned to ground through
RF level and modulation percentage are measured by
R200 and R203. Also, the input voltage to the regulator
two volt- meter circuits, incorporating V115A and V115B
circuit is bled through R197, R200, and R203, so that
and indicated by meters M101 and M102. External voice
any change in input voltage will produce the same effect
modulation may be obtained through a microphone
as a change in output voltage. The ripple current
connected to MIC jack J108. Other external modulation
through C158 will produce a voltage drop across R203
is connected to EXT MOD binding posts on the front
which will tend-to oppose any ripple that does appear at
panel.
the input point of the regulator circuit. Resistor R201
maintains the flow of operating current through V112.
Resistor R199 is the screen voltage-dropping resistor for
high voltages for the operation of Test Set, Radio
V113. In case of transient load variations, such as motor
AN/ARM-5A are from a regulated power supply. The
surges, C159C produces a corrective voltage at-the grid
115-volt alternating current (ac), 60-cycle, primary power
of V113 of a greater magnitude than would the voltage
is connected at POWER INPUT connector J106 and
from the divider.
controlled by POWER STANDBY switch S106. For
Modulation
circuit protection, both sides of the input line are fused by
frequencies in the AN/ARM-5A are produced by tone
F101 and F102. With S106 at STANDBY, primary power
generator MG101. The modulation frequencies are
is supplied to the space heaters. Switching S1Q6 to
derived from tone wheels ElO1A and E101B, which are
POWER applies primary volt- age to transformers T101
mounted on a common shaft and driven by motor B101,
and T102 of the power supply and applies power to
a 60-cycle, 1,800-revolution per minute (rpm)
motor B101 of tone generator MG101. The regulator
synchronous motor. Each tone wheel has teeth so cut
circuit is de- signed to compensate for input voltage
as to generate a frequency-modulated signal with a
variations as well as load-voltage variations. The direct
9,960-cycle center frequency. On one wheel (E101A),
current (de) output from rectifier V11, filtered by a single-
the modulation frequency is 30 cycles, that is, 1 cycle per
section choke-input filter, consisting of choke L121 and
revolution of the wheel. This
capacitor C158, is connected in series with series
regulator V114. The load current through V114 is
dependent on TM 11-6625-4$' 45 the grid bias applied to
1-3
