Thales 421, Эксплуатация и обслуживание, Страница: 103 / 256

LLZ 421
Operation and Maintenance Alignment Procedure LLZ−1F (Dip./Refl.)
ILS 420
4−13
Ed. 01.10 SOAC
4.4.2 Adjustment Procedure of Standby Channels
See Fig. 4−2, 4−4, 4−8.
4.4.2.1 Stby CRS Posn. Channel
(Input connector J2)
− Connect oscilloscope to TP47 and TP59 (GND). Measure output level.
Adjust IF gain to achieve approx. 3.6 Vpp output: R499 is set to mid position. Perform first coarse
alignment removing or inserting attenuators with JP2,3; perform fine adjustment with R2. Phase
adjustment with R123 is factory set and not needed for Posn. channel.
4.4.2.2 Stby CRS Width Channel
(Input connector J6)
− Connect oscilloscope to TP49 and TP59 (GND). Measure output level.
Adjust IF gain to achieve approx. 3.6 Vpp output: perform first coarse alignment removing or insert-
ing attenuators with JP4, JP5; perform fine adjustment with R25. Check relative CSB − SBO phase
with oscilloscope, measure between TP1 (CSB) and TP5 (SBO), see Figs. 4−5, 4−8. Adjust with
R136 (and R123 if needed) to 0°. R123 is normally factory set. If need be readjust R499 for CSB
component level. Stby CRS Width DDM is defined by CSB/SBO ratio set with R25 and R499. Finally
adjust output level with R133 to 3.6 Vpp.
IF gain set
R2
Stby CRS CSB
J2
TP72
out
CRS Posn. Stby
TP2
R499
JP2
in
TP47
TP1
input attenuation* Output level
−15 dB −10 dB
Phase adjust
3.6 Vpp
R123
JP3
IF gain set
R25
Stby CRS SBO
J6
CRS Width Stby
TP4
JP4
in
TP5
input attenuation*
Output level
−10 dB −10 dB
Phase adjust
R136
JP5
TP3
signal inversion
TP73
out
TP49
3.6 Vpp
R133
rel. Phase CSB − SBO =0°
set to mid position*
factory
field
setting depends on local conditions
0/180°
mid position*
set to mid position: 3.7k*
1.5Vpp
ca. 0.16Vpp
ca. 3.2Vpp
ca. 0.16Vpp
ca.
* initial setting
TP59, TP30
GND
Fig. 4−4 Adjustment of detector channels for standby monitoring
Phase adjustment, using delay trigger option
Signal A (e.g. TP1 CSB)
Signal B (e.g. TP5 SBO)
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
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
Fig. 4−5 Relative phase adjustment of Stby CSB/SBO