Thales 421, Эксплуатация и обслуживание, Страница: 124 / 256

LLZ 421
Alignment Procedure LLZ−2F (Dip./Refl.) Operation and Maintenance
ILS 420
5−10
Ed. 07.08 SOAC
c) Set parameter ’CLR CSB RF−Level’ of both TX to 0 W.
d) Set parameter ’CLR SBO Amplitude’ of both TX to 0 %.
e) Set parameter ’CRS CSB RF−Level’ of both TX to 25 W.
f) Set parameter ’CRS SBO Amplitude’ of both TX to 30 %.
g) Measure DDM with portable DDM instrument at a distance of approx. 1000 m (test point A or A’,
Fig. 5−7) and at approx. 2° away from course line; then set ’CRS SBO Phase’ so that the instru-
ment indicates DDM 0 (Phase in Quadrature).
NOTE: Range of values 0...359°
h) Read out phase value determined in g). Then add or subtract 90° to or from it and enter as new
value, so that150 Hz predominates to the left of the course line, as seen in the radiation direction.
If not, a further 180° must be either added or subtracted (Normal Phase).
i) Set TX2 on aerial and repeat the phasing for TX2 with steps b) to h).
j) Switch both TX off.
5.3.4 Set CSB/SBO Phase (Clearance)
a) Switch both TX on and set TX 1 on aerial.
b) Open dialog ’Transmitter1−Waveform Data#1’, open dialog ’Transmitter2−Waveform Data#1’.
c) Set parameter ’CRS CSB RF−Level’ of both TX to 0 W.
d) Set parameter ’CRS SBO Amplitude’ of both TX to 0 %.
e) Set parameter ’CLR CSB RF−Level’ of both TX to 25 W.
f) Set parameter ’CLR SBO Amplitude’ of both TX to 30 %.
g) Measure DDM with portable DDM instrument at a distance of at least 150 m (at measurement
circle) and at approx. 25° (min. of clearance DDM) away from course line; then set ’CLR SBO’
Phase so that the instrument indicates DDM 0 (Phase in Quadrature).
NOTE: Range of values 0...359°
h) Read out phase value determined in g) then add or subtract 90° to or from it and enter as new value,
so that when seen in the radiation direction, 150 Hz predominates to the left of the course line.
If not, a further 180° must be either added or subtracted (Normal Phase).
i) Set TX2 on aerial and repeat the phasing for TX2 with steps b) to h).
j) Switch both TX off.
5.3.5 Check SBO null of Course Antenna
The DDM null must not deviate from the nominal course line by more than ±10 cm at a distance of
150 m from the LLZ antenna, and the DDM must rise in a linear fashion from the null on either side.
If not, the dipoles must be phased in pairs. To perform this procedure refer to the appropriate Part
3 of the LLZ−manuals: Antenna System Description for Dipole/Reflector Antenna, Chapter 5.