Section VI
Paragraphs 6-44 to 6-4
cover on the front panel to obtain an oscillator fre-
b. Connect this signal into the navigation receiver
quency of 1000 200 cps as measured with an oscil-
and read the 30 cps voltage developed at the receiver
loscope and audio oscillator using Lissajous patterns.
detector with an a-c vacuum tube voltmeter. Also
read the receiver avc voltage with a d-c vacuum tube
6-45. MODULATION PERCENTAGES. The modula-
tion levels can be adjusted with the test setup shown
in figure 5-1. The modulation levels are stable and
c. Substitute Signal Generator SG-13/ARN for Signal
will seldom need resetting. A substitution method is
Generator SG-l/ARN and Modulator MD-83A/ARN.
used to set the audio levels on Signal Generator
Adjust SET LINE TO 21V, METER ZERO and CAR-
RIER SET controls. Adjust the MICROVOLTS dial
SG-13/ARN. A signal from Signal Generator SG-
l/ARN and Modulator MD-83A/ARN is fed into a navi-
until the same receiver avc voltage is obtained as in
gation receiver. The avc and detector audio voltages
step b above. The MICROVOLTS dial should read ap-
of the receiver are noted. A similar signal from Sig-
proximately 1000 microvolt.
nal Generator SG-13/ARN is then applied to the re-
ceiver and the levels adjusted to repeat the noted
d. With the AUDIO SELECTOR on the 30
VAR
readings. In all the alignment procedures that follow
position, adjust the 30
LEVEL SET control (figure
a 53-ohm 6-db attenuator pad is used between the r-f
cable from the SG-13/ARN to the input connector of
tained as in step b. Lock the 30
LEVEL SET con-
the navigation receiver. In all of the following proce-
trol.
dures the r-f output cable is connected to the NAV
OUTPUT connector and the NAV-GS switch must be in
6-47. 9960 FM MODULATION LEVEL. With the
the NAV position.
AUDIO SELECTOR in the 9960 FM position set the
9960 FM LEVEL SET control (figure 6-11) to 30 per-
cent modulation using the same procedure as described
in paragraph 6-46, above.
a. Set up Signal Generator SG-1/ARN to read 500
microvolt at 110.1 mc and modulate it with 30 cps at
30 percent modulation as read on the SG-1/ARN mod-
AUDIO SELECTOR in the 1000
position, adjust the
ulation meter.
1000
LEVEL SET control (figure 6-11) to 30 percent
