User's Manual

Model 1150A DVOR
3-36 Rev. - November, 2008
This document contains proprietary information and such information may not be disclosed
to others for any purposes without written permission from SELEX Sistemi Integrati Inc.
3.6.8.1.1.2 Notch Monitor Data Screen
The Notch Monitor Screen is shown in Figure 3-32. This screen displays the Notch Monitor data from the associated
Monitor. The monitor measures the signal from the Field Monitor for “notches” in the detected signal. A notch
indicates a fault in one or more transmitting antennas, feed cables or commutator switch channels. When a failure
occurs in one of these channels there is a lack of signal and therefore a notch in the detected signal pattern. The
1150A DVOR is a double sideband configuration and therefore there are four sideband antennas on at any one time.
Therefore the notch will not fall to zero but since three other antennas are contributing to the signal only a reduction
in signal can be expected.
The Record baseline button is used when the technician is confidant that the DVOR is operating properly, such as
following a flight inspection of the facility. When the Record Baseline button is pressed, the current data is copied
into memory as the “Baseline” Data and then used as the reference. If the Sideband power is varied, then a new
baseline will be required. When the measured signal differs from the Baseline by more than the Notch Monitor
tolerance set in the Monitor Alarm Limits screen, the alarm (red) or alert (yellow) indication is generated, depending
on if the Notch Monitor is configured as a Primary or Secondary Alarm.
The tolerance for notch monitoring should be set to approximately 20% in the Monitor Alarm Limit screen, but the
technician can adjust this tolerance as needed for more or less sensitivity. Note that when one antenna fails there will
typically be an out-of-tolerance indication for one to four of the possible radiating antennas. When an out of
tolerance condition exists, the Sideband VSWR data screen should be reviewed as well. If there is an indication of
Sideband VSWR alarm, investigate the VSWR alarm indication first.
Figure 3-32 Notch Monitor 1 & 2 Data