©1999 Navia Aviation AS 21833-3.4 Maintenance Procedures
OPERATING MANUALNORMARC 7013
INSTRUMENT LANDING SYSTEM
C-21
from the PMDT: Open the TX Adjustments window. Select COURSE RF Power (for active
transmitter to antenna). Note the 3-digits value.
(b) Then reduce the value of the 3-digits number followed by Update until the monitor chan-
nel CL is in alarm. Measure and record the COU CSB dc voltage at the transmitter test con-
nector.
(c) Measure the carrier power using the BIRD wattmeter connecting to the course CSB feed-
line inside the facility.
(d) Restore the carrier rf power to normal (original 3-digit value).Measure and record the car-
rier power still connecting the BIRD wattmeter to the course CSB feedline inside the facility.
(e) operating tolerance in chapter 3.
(f) Remove the wattmeter from the carrier feedline.
10.Clearance transmitter. Repeat steps (8) and (9).
NOTE:
The FA-9438 modulation meter may not accurately measure the high 150 Hz modulation per-
centage. In this case, use the alternate procedure explained in paragraph 5-47.
11.Restore the facility to service.
5-46 Reserved.
5-47 90 AND 150 Hz MODULATION PERCENTAGES.
a. Object.
This procedure provides a method to determine the amplitude modulation percentages of the
90 and 150 Hz navigational tones.
b. Discussion.
1. The FA-9438 modulation meter (or equivalent) is the primary standard for the measure-
ment of modulation percentage. Other equivalent pieces of test equipment could include a
portable ILS receiver (PIR) capable of measuring modulation directly or built-in test equip-
ment (BITE). These may be substituted for the FA-9438 when properly calibrated and/or
verified for accuracy. The oscilloscope method is a backup method that uses the detected
composite carrier envelope for determining the approximate percentage. The oscilloscope
reference values should be noted when flight inspection or FA-9348 modulation meter have
been used to measure modulation.
2. If flight inspection reports the modulation out of tolerance, reconfirm your measurement. If
the measurement is within the FA-9438 or BITE that has been verified with the FA-9438,
To Next Page
Loading...