TM 11-6625-828-45
wheel is surrounded by pickup coils L101, L102, L104,
90 setting provides modulation
and L105. Voltages generated in selected pairs of these
corresponding to the signal received due west of the
coils are used in the formation of signals for omni
omni station, and so forth.
modulation. The other wheel (E101B) is frequency-
modulated by equal components of 90 cycles,
corresponding to 3 cycles per revolution of the wheel,
V1O1B and variable channel amplifier V103A, V103B are
and 150 cycles, corresponding to 5 cycles per revolution.
similar, each being a triode amplifier designed to
Coil L103 is used with E101B to generate the localizer
increase the respective channel modulations derived
modulations. Capacitors C102 through C106 are used to
from tone generator MG101 to a suitable level.
tune the coils to a broad resonance at 9,960 cps. The
9,960-cycle signal frequency-modulated at 30 cycles as
channel limiter CR101, CR102 circuit and variable
generated by E101A, is amplified, limited, and applied to
channel limiter CR103, CR104 circuit differ slightly in
modulator tube V102 as the reference modulation
circuit values, but function identically within their
component for omni signal. The 30-cycle modulation, or
respective channel circuits. They limit the upper and
90-cycle and 150-cycle modulation for localizer signals,
lower peaks of the input signals symmetrically, thereby
is obtained by discriminating and filtering the frequency-
removing amplitude variations, and perform as follows:
modulated output of the appropriate tone wheel pickup
The limiter in its quiescent state (no signal in- put) may
coil.
be considered as a resistor network in which the current
f. MODULATION
Switch
through R128 divides equally through R127 and R129
MODULATION switch S102 is a rotary switch with ten
active positions which, when set to the-proper position,
current flow from R127 to R128, and similarly, from,
selects the type of emission desired from the AN/ARM-
R129 to R128. ' - If the voltage at the cathode of CR103
5A. There are three amplitude localizer (AMP LOC)
is reduced, due to an applied signal, the voltage at the
standard positions on this switch corresponding to off
anode of CR103 will also be reduced, as will the voltage
course- needle right, off course-needle left, and one
at the anode of CR104. If the potential at the anode of
course signals. A single switch position OMNI selects a
CR104 reaches ground potential or attempts to go lower,
standard omni signal. In addition to the standard AMP
no current can flow because of the rectifier action of the
LOC and OMNI positions, four SET positions, 30, 90,
anode and cathode of CR104. The negative swing of the
150, and 9,960 cycles, are included. The EXT position is
input signal is limited. Circuit values are chosen so that
used for setting the RF level or for external modulation.
the voltage at CR101, CR102 circuit may be reduced to
g. OMNI TRACK Switch (fig. 1-4). OMNI
ground potential, but no further. If the voltage at the
TRACK switch S101 selects, from pickup coils L101,
cathode of CR103 increases, the action is relatively the
L102, L104, and L105, the pair of coils which determines
same, with component values chosen so that the voltage
the phase relationship between the 30-cycle. frequency
at CR101, CR102 circuit will rise to twice the no-signal
modulation on the reference-phase component of
voltage and no further, resulting in the limiting of the
modulation, and the 30-cycle variable-phase component
positive swing. The action of reference channel limiter
of modulation. By selecting these coils in proper
CR101, CR102 circuit (fig. 1-7) is the same. In the
combination, S101 is capable of shifting the track angle
variable channel circuit, the output is applied to the grid
through 360 in twelve 30 steps.
The angular
of V104A, which serves to amplify the limited signal
relationship between various paired coils is shown in
present at the output of CR101, CR102. Resistor R109
(fig. 1-7) is
used to
adjust the level of
the 9,960-cycle
an additional phase shift is introduced by the connection
modulation component to its proper value. Resistors
of a phase- shifting circuit consisting of R142, R143, and
C122. This circuit is connected between the 30- cycle
modulation level of the 30-cycle or 90 plus 150-cycle
filter and modulation amplifier V104B.
The OMNI
components.
TRACK switch is calibrated in angle to degrees to
simulate an omni transmitter. At a zero-degree setting of
S101, the emitted signal 1-4 is the same as that which
would be received by an aircraft due south of an omni
1-4