User's Manual

SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
ARINC 781-200 SDU and SCM
23-15-30 3-10
DATE TBD
The MCDU displays the overall PIM status and results for each direction. If the overall
status is PASS, the SDU can continue to use SBB services.
If the overall status is FAIL:
• Check the cable connections of the antenna and the SDU.
• Check the direction in which the test failed and verify that the antenna is not
blocked in that direction—see
"Directional PIM Test Results" on page 3-10.
(2) Directional PIM Test Results
The SDU performs the PIM test with the antenna pointing in different directions and
displays the results of the test in each direction. If the overall status of the PIM test
is FAIL, you can check the specific directions in which the test failed.
For each direction, the PIM test results provide:
• Overall Status—pass or fail.
• The direction coordinates.
• The signal degradation—the maximum value to pass the test is 3 dB.
• Possible interference—interference caused by environmental factors, not the
SDU transmit frequencies. Interference indicates that the SDU received a signal
in the receive band even when it wasn’t transmitting, therefore an external signal
may be interfering with communication in that direction.
• Signal and noise levels before and after the test—the SDU uses this information
to check for possible interference.
7. Installation and Engineering Drawings
This section contains the Outline and Installation diagrams, and Interconnection and Contact
Assignment drawings for the SDU and SCM.
All foldout pages are odd-numbered and not-backed for print production purposes.
A. Outline and Installation Drawings
The Outline and Installation drawings on pages 3–11 to 3–17 show the physical
characteristics of the SDU and SCM, and provide installation data for the system.
B. System Interconnect Drawings
System Interconnect drawings on pages 3–19 to 3–23 show the interconnection details
for the SDU and SCM.