TM 11-6625-821-45
1-9. Tuning Control
Selection
The control unit tunes the receiver over each
a. Function selection (fig, 5-11). Control
frequency range by remotely controlling a ser-
unit function switch S302 connects 27.5 volts
vomechanism that is connected mechanically to
dc to the receiver and selects one of the three
a variable capacitor in the receiver. When
operating modes of the receiver When f unc-
control unit function switch S302 is moved
tion switch S302 is set to any position other
from OFF to ADF, ANT, or LOOP posi-
than OFF, 27.5 volts dc from the test set pow-
tion, 26 volts, 400 cps from the test set power
er circuit ( para 1-4) is applied through con-
circuit is connected to the rotor of tuning
tacts 9.5 and 11 of rear switch wafer S302B
synchro B301. This voltage also is connected
and out pin L on connector P301. This voltage
through rear switch wafer S4D in the test set
is applied to the receiver through front and
to the rotor of the servomechanism in the re-
rear switch wafers S4D in the test set. When
ceiver. The rotor in tuning syncro B301 in-
function switch S302 is set to ADF, front
duces a voltage into its stator windings. Front
switch wafer S302B connects 27.5 volts dc to
and rear switch wafers S4A conned these volt-
the antenna and loop mode circuits and opens
ages to the stators in the servomechanism in
the ADF mode circuit. The voltage for the an-
the receiver. A magnetic field is then set up
tenna and loop circuits is connected to the re-
in the receiver servomechanism that has the
ceiver through front and rear switch wafers
same direction and phase as the magnetic
S4A. Setting function switch S302 to the ANT
field set up by the rotor in tuning synchro
position applies 27.5 volts dc to two of the op-
B301. The rotor in the receiver servomechan-
crating mode wires (ADF and LOOP) while
ism will therefore be in the same' position as
leaving the third operating mode wire (ANT)
the rotor in tuning synchro B301. Since the
open. Test set rear switch wafer S4A connects
rotor in tuning synchro B301 is geared to the
the 27.5 volts dc from ADF and LOOP mode
TUNE control, the receiver is remotely tuned
wires to the receiver. When function switch
by rotating the TUNE control.
S302 is set to the LOOP position, front switch
wafer S302B connects 27.5 volts dc to the
ADF and ANT mode circuits and opens the
LOOP mode circuit. Front and rear switch
The manual loop control circuit supplies a
wafers S4A connect the 27.5 volts dc from the
ground or either one of two phases of a 110-
ADF and ANT mode circuits to the receiver.
cps signal to a manual loop control circuit in
b. Frequency Range Selection (fig. 5-11)
the receiver. This manual loop control circuit
When selecting any one of the three fre-
in the receiver supplies a signal which drives
quency ranges of the receiver, range switch
the servo-driven goniometer. Two phases of
S304 connects 27.5 volts dc to two frequency
110-cps signals, derived from receiver 110-cps
range circuits and connects ground through a
oscillator Q22, are applied through f rent and
25-ohm resistor to the desired frequency range
rear switch wafers S4B in the test set to
circuit. If, for example, range switch S304 is
LOOP switch S303 in the control unit. Switch
set to the 190-400 position, rear switch wafer
S303 has two positions, R (right) or L (left),
S304 connects 27.5 volts dc to the 400- to
with spring return to its center or grounded
850- to 1,750-kc range circuits. Front switch
wafer S304 connects ground through resistor
position. In the center position, LOOP switch
R308 to the 190- to 400-kc range circuit. Front
S303 applies ground to the manual loop con-
trol circuit in the receiver through front
switch wafers S4C an S4D in the test set con-
switch wafer S4B and GONIO DRIVE switch
nect the 27.5 volt dc from the two frequency
range circuits (400850 kc and 850-1,750 kc)
S2. The receiver requires this ground in order
to the receiver. Ground through a 25-ohm
for the servo-driven goniometer to operate
resistor (R308) is connected to the receiver
properly when the receiver is in the ADF
through rear switch wafer S4B.
mode. GONIO DRIVE switch S2 provides the
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