Section IV
Paragraphs 4-6 to 4-11
4-6.
TONE LOCALIZER CENTERING ACCURACY
c. Modulate the SG-2 with a zero db glide slope
CHECKS .
signal and adjust the receiver for zero crosspointer
current. (Consult receiver handbook for location of
a. Connect an SG-1/ARNsignal generator modulated
adjustment. )
with an MD-83A/ARN to an ARN-14 navigation re-
ceiver equipped with a precision crosspointer meter.
d. Using the same 6-db pad, substitute the SG-13
Use a 6-db, 53-ohm attenuator pad at the receiver
/ARN for the SG-2 and set its frequency to 332.0 mc.
input. See figure 8-5.
See figure 8-6, part 2.
b. Set the frequencies of the receiver and signal
e. Set the SG-13/ARN MICROVOLTS dial to 1000
generator to 110.1 mc, and set the MICROVOLTS
and set the SG-13/ARN for an "ON COURSE" glide
dial of the signal generator to 500.
slope signal (LOC-GS control to top center panel
mark). The crosspointer current reading should be
0 12 microampere.
c. Modulate the SG-1/ARN with a zero db tone
localizer signal and adjust receiver for zero cross -
4-9. GLfDE SLOPE 3-DB ACCURACY CHECK.
pointer current. (Consult receiver handbook for lo-
cation of adjustment. )
a. Repeat steps a and b of paragraph 4-8.
d. Substitute the SG-13/ARN for the MD-83A/ARN,
b. Modulate the SG-2 with a 2-db UP glide slope
SG-1/ARN combination using the same 6-db pad, and
signal and adjust the ARN-18 glide slope receiver for
set the MEGACYCLES control to 110.1. Allow SG-13
/ARN to warm up at least 15 minutes and adjust SET
90 microampere crosspointer current.
(Consult
LINE TO 21V switch for 21V 0.5V on panel meter.
receiver handbook for location of adjustment.)
Set METER ZERO and adjust carrier level to red line.
c. Substitute the SG-13/ARN for the SG-2 and set
the SG-13/ARN frequency to 332.0 mc.
e. Set the MICROVOLTS dial to 1000 and set the
SG-13/ARN for an "ON COURSE" tone localizer signal
d. Set the SG-13/ARN MICROVOLTS dial to 1000
(LOC-GS control to top center panel mark). The
and set the SG-13/ARN for a 3-db UP glide slope
cross pointer current reading should be 0 8 micro-
signal. (Top mark on the course width sector.)
ampere.
4-7. TONE LOCALIZER 6-DB ACCURACY CHECK.
e. The crosspointer current should be 135 18
microampere.
a. Repeat steps a and b of paragraph 4-6.
f. Repeat steps b, c, d and e for a 3 db DOWN
b. Modulate the SG-1/ARN with a 4-db LEFT tone
setting.
localizer signal from MD-83A/ARN and adjust the
navigation receiver for 90 microamperes cross pointer
4-10. Failure of the SG-13/ARN to meet the above
current. (Consult receiver handbook for location of
VOR, TONE -LOC, and GS accuracy requirements
adjustment.)
usually indicates that one or more of the audio signals
involved is not set to the correct frequency or per-
c. Substitute the SG-13/ARN for the MD-83/ARN,
centage modulation. Excessive distortion can also
SG-1/ARN combination and set its frequency to 110.1
cause inaccuracy.
mc.
4-11. MAJOR INSPECTION. (Not to exceed 500 hrs).
d. Set the MICROVOLTS dial to 1000 and set the
SG-13/ARN for a 6-db LEFT tone localizer signal.
(Top mark on the course width sector. )
a. Remove SG-13/ARN from case.
b. Remove top and bottom covers from RF chassis
e. The crosspointer current should be 135 15
and clean inside with a soft brush or vacuum cleaner.
microampere.
c. Check the signal generator and dynamotor for
f. Repeat steps b, c, d and e for a 6-db RIGHT tone
mechanical damage, loose parts, and signs 01 over-
localizer setting.
heating and corrosion.
4-8. GLIDE SLOPE CENTERING ACCURACY CHECK.
d. Check the dynamotor brushes for a minimum
length of 1/4 inches. Replace if necessary. See
a. Connect an SG-2 signal generator through a 6-db
Section VII, paragraph 7-18.
53-ohm attenuator pad to an ARN -18 glide slope
receiver equipped with a precision cross pointer
e. Check the dynamotor commutator for evidences
meter. See figure 8-6, part 1.
of grooving or pitting. Dress or replace if necessary.
See Section VII, paragraph 7-17.
b. Set the frequencies of the signal generator and
receiver to 332.0 mc and set the SG-2 microvolt dial
f. Lubricate equipment as follows:
to 500.
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