Thales 421, Эксплуатация и обслуживание, Страница: 130 / 256

LLZ 421
Alignment Procedure LLZ−2F (Dip./Refl.) Operation and Maintenance
ILS 420
5−16
Ed. 07.08 SOAC
Phase adjustment, using delay trigger option
Oscilloscope setting:
Channel 1
CSB
Channel 2 SBO, position below or on same line
V/div. 0,5
Trigger internal, channel 1 (or ext., from LGA, TP11)
Time sweep 0.1 ms; delayed: 50 us
Time delay Adjust to show a sine curve segment
CSB
SBO
delayed trigger point
Signal A (e.g. TP1 CRSCSB, TP19 CLRCSB): standby
Signal B (e.g. TP5 CRSSBO, TP23 CLRSBO): standby
NOTE:
For more clear representation the use of an analog oscilloscope is recommended. For the phase align-
ment procedure, the delayed trigger segment of 50 us has to be in a range of the signals where the ampli-
tudes rise in the same direction to get correct phasing. Check the trigger position of the signal if the result
seems to be in the opposite phase range (e.g. 180° rotated); read also monitor result in the PC User Pro-
gram (ADRACS or MCS) for correct sign. If the phase cannot be adjusted insert phase adapters or phas-
ing cables to achieve a sufficient setting range of the potentiometers.
Recommended measurement procedure:
Adjust the scope so that both signals are equal in amplitude. Turn on the ADD and INVERT functions.
Make the signal now created on the scope as flat as possible. This will ensure the signals are within a cou-
ple of degrees. It is very important that these two signals are in phase.
50 us
(use maximum of SBO)
Fig. 5−5 Relative phase adjustment of Stby CSB/SBO for CRS and CLR
5.4.3 Calibration and Normalization of Integral Monitors
NOTE: Before performing this procedure it is recommended to check alarm limits acc. 5.4.5.
a) Switch both TX on and set TX1 on aerial.
5.4.3.1 Integral Monitoring Posn. (DDM 0 %)
a) RF−level of the corresponding path on the SOAC (Fig. 5−2, 5−3) is set to amplitude of 3.6 Vpp
as described in 5.4.1.
b) Set indicated DDM to 0 by inserting phase adapters in coupling lines from dipoles. Watch the DDM,
measured with the portable DDM instrument connected to the output Pos. Integral of the integral
network in the antenna distribution unit (ADU).
NOTE: If any corrections are necessary, start with dipole pairs whose nulls have been corrected by
inserting phase adapters.
c) Open dialog ’Monitor1−Nominal Values’ and open dialog ’Monitor2−Nominal Values’. Enter the
measured values for the parameters ’EXEC CRS Position DDM’ and ’EXEC CRS Position SDM’.
d) Open dialog ’Transmitter1−Waveform Data#1’. Note down the values of ’CRS SBO Amplitude’
and ’CLR SBO Amplitude’. Set them all to 0. Set ’ILS Ident keying’ to 10 % and ’continuous’.
e) Send to Monitor1/2 the command ’Calibration, Executive CRS Position detector’.
f) Restore TX1 SBO settings of 5.4.3.1 d) back to normal.
g) Send to Monitor1/2 the command ’Normalization, Executive CRS Position detector’.
NOTE: The automatic normalization procedure runs only if the actual DDM and SDM values do not
vary to much from the nominal values !