TM 11-6625-828-45
network is a filter for the onmi circuit to eliminate
harmonics and high-frequency components.
individual setting of the modulation level for the 9,960-,
i. 15 Phase Shift Network. When selected,
30-, 90-, and 150-cycle components. The modulation
the 15 phase shift network adds 15 to the phase of the
percentage of each of these modulation components is
filtered 30-cycle signal.
adjusted to the N. proper value by means of separate
j. Modulation , Amplifier. Modulation amplifier
potentiometers following the limiter circuits. The circuit is
designed so that when the 30- and 9,960-cycle
V104B amplifies its various input signals to a level
components are properly adjusted to 30 percent
sufficient to drive modulator V102.
k. 1,000-Cycle Oscillator. The 1,000-cycle
modulation, the needle of %M meter M102 will align with
the green arrow on the dial. When the 90- and 150-cycle
oscillator (V107) supplies 1,000-cycle signals to
components are properly adjusted to 20 percent
modulation amplifier V104B. Oscillator V107 is keyed by
modulation, the needle of M102 will point to the red dot
oscillator keyer V106 when IDENTIFIER switch S104 is
on the dial. First, adjust the 90-cycle component and
in the ON position to identify a radiated test signal.
then adjust the 150-cycle component.
l. Modulator. Modulator V102 amplitude-
modulates (am.) the radio frequency (RF) signals
30-cycle tone wheel coils (L101, L104, L105, and L102)
generated in RF unit Z104.
are connected to OMNI TRACK switch S101. These
m. RF Unit. Rf unit Z104 generates an RF
coils are disposed around tone wheel E1O1A at precise
voltage of known amplitude which is controlled by RF
angular spacings of 0, 30, 120, and 180. Switch
attenuator Z105. This output is available at ATTEN jack
S101 selects these coils in pairs, in various
J104. Also, a 1-volt output is available at I VOLT jack
combinations, and with MODULATION switch S102 in
J105. The RF voltage is modulated by the frequency
the OMNI position, connects one to the input of
selected at MODULATION switch S102. The RF output
reference amplifier V101 and the other to variable
is demodulated by cathode follower V116A and is
amplifier V103. For zero-degree track, the same coil is
available at DEMOD jack J107.
connected to both channels. The output of V101 is
clipped symmetrically by the twin, crystal diode limiter
1-4.
Stage Analysis
CR101, CR102, and applied to modulator tube V102 as
Test Set, Radio AN/ARM-5A produces crystal- controlled
the reference-phase component of modulation. The
RF signals that are amplitude-modulated by any of three
output of V103 is clipped by crystal diode limiter CR103,
types of internally generated signals. These are omni,
CR104, and amplified by V104A, and then discriminated
localizer, and 1,000-cycle signals. The omni signal
by net- work Z101 and CR105, CR106. The resulting
consists of an RF signal simultaneously amplitude-
variable phase 30-cycle signal is fed through a 30-cycle
modulated with 30 cycles known as the variable 30-
filter for the elimination of harmonics and then through a
cycle component and 9,960-cycle subcarrier component.
phase-shifting resistance network to modulation amplifier
The subcarrier is frequency-modulated at a 30-cycle rate
V104B. The signal, after being amplified by V104B, is
(known as the reference 30- cycle signal). OMNI
applied to modulator V102 as the variable-phase
TRACK switch S101 determines the phase angle
component of modulation,
between the variable and reference 30-cycle signals.
The localizer signal consists of an
RF
signal
simultaneously amplitude-modulated with 90- and 150-
11). With the MODULATION switch set to any of the
cycle components. On course indicates equality of these
three AMP LOC positions, the input to the reference
components. Off course indicates inequality, with the
phase channel is disconnected from the tone generator
150-cycle component predominating for needle left and
and grounded. Amplitude localizer pickup coil L103,
the 90-cycle component predominating for needle right.
associated with tone wheel E101B, is connected to the
The third type of signal is 1,O00-cycle internal
variable-phase channel. Amplitude localizer tone wheel
modulation or the RF signal may be externally modulated
E101B is cut to provide a 9,960-cycle signal, frequency-
by an audio- frequency or voice signal, The various
navigational signal outputs generated by a tone
generator are selected by means of MODULATION
switch S102, located on the front panel. Switch S102
1-2
