Section II
Paragraphs 2-9 to 2-11
g. Test the omni-bearing indicator and cross pointer
NOTE
sensitivity to small omni-bearing changes with the +1
DEGREE switch. Consult the receiver handbook for
Complete receiver testing using Antenna AT-
acceptable tolerances. Tap the instruments lightly
170/ARN is recommended only after communi-
before reading if the engines are not operating.
cation officers correlate signal strengths ob-
tained outside the aircraft using the antenna
h. Rotate the omni-bearing selector knob through
with those obtained when Signal Generator SG -
360 degrees and note operation of the TO-FROM indi-
13/ARN is directly connected to the receiver.
cator.
Such correlation must be carried out for each
type of aircraft since the receiving antenna
i. Tune Signal Generator SG-13/ARN and receiver
location may vary with each type of aircraft.
to desired frequency in the 118 to 135.9 mc band. Set
Further, position of Antenna AT-170/ARN with
meter to red line with CARRIER SET control.
r e s p e c t to the receiving antenna must be
specified and maintained for each type of air-
j. Check the receiver's aural output by placing the
craft. Unless this procedure is carefully ad-
hered to wide discrepancies in flag sensitivi-
SG-131/ARN AUDIO SELECTOR switch in the 1000
position and listening for the tone in the receivers
ties may exist. See figure 2-4 for signal
headset.
levels observed in a typical situation, where
a nearby obstruction causes a dissymmetry in
the field strength pattern.
the localizer operation of navigation receivers follow
the procedure outlined below.
a. Carry out adjustments listed under paragraph
2-3, above.
check the omni-range operation of navigation re-
ceivers follow the procedure below.
b. Make connections in accordance with instructions
in paragraph 2-7 above.
a. Carry out adjustments listed under paragraph 2-3.
c. Turn AUDIO SELECTOR to TONE LOC and NAV-
b. Make connections in accordance with instructions
GS switch to NAV position.
in paragraph 2-7 above.
d. Tune Signal Generator SG-131/ARN and receiver
c. Turn AUDIO SELECTOR to VOR position, and
to desired channel in 108 to 110.9 mc band. Set meter
NAV-GS switch to NAV position.
to red line with CARRIER SET control.
d. Tune Signal Generator SG-13/ARN and receiver
Rotate the MICROVOLTS dial on Signal Generator
to desired frequency in the 112.0 to 117.9 mc band.
e.
SG-13 clockwise until the flag alarm OFF indicator on
With the METER switch in CAR position, set meter to
the receiver's course deviation indicator disappears
red line with CARRIER SET control.
from the vertical bar. Consult the receiver handbook
for correct flag sensitivity values.
e. Rotate the SG-13/ARN MICROVOLTS dial clock-
wise until the flag alarm OFF indicator on the re-
f . Rotate the LOC-GS control over the range
ceiver's course deviation indicator disappears from
Covered by the left segment and note the amount of
the vertical bar. Compare the resulting MICROVOLTS
cross pointer deflection to the left. With the LOC -GS
setting with the flag sensitivity value called out in the
control set at the middle of the left segment the
navigation receiver handbook.
vertical bar of Course Indicator ID-249A/ARN should
be displaced to the second dot on the left.
f. Select an omni-bearing on the VOR switch. Use
a MICROVOLTS setting of 1000 microvolt. Center
the vertical bar of the course deviation indicator with
NOTE
the receiver omni-bearing selector. The COURSE
indication should read the same as the setting on the
Tests in paragraphs f. and g. are based on a
SG13/ARN VOR switch setting. Consult the receiver
standard localizer receiver sensitivity of 90
handbook for acceptable tolerances. Repeat for the
microampere deflection for a 4 db ratio be-
remaining seven radial settings of the VOR switch.
tween tones.
NOTE
g. Rotate the LOC-GS control over the range
covered by the right segment and note the amount of
The VOR switch setting provides an output
crosspointer deflection to the right. With the LOC-GS
signal simulating that received by an aircraft
control set at the middle of the right segment the
flying to a ground station. Therefore the course
vertical bar of Course Indicator ID-249A/ARN should
indication noted above reads the same as the VOR
be displaced to the second dot on the right.
switch setting only when the TO-FROM indicator
reads TO. The vertical bar may be centered
h. Check crosspointer centering by turning the LOC-
with the indicated course reading 180 degrees
GS control to the white center sector. The cross-
from the VOR switch setting, in which case the
pointer should be centered when the LOC-GS control
TO-FROM indicator would read FROM.
is within this sector.
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